CHAPTER XI.

Cobalt, as furnishing a blue colour, is usually associated with alumina, silica, or tin; and, as furnishing a green colour, with zinc. But there is obtainable a compound of zinc and cobalt which gives a blue not only free from green, but inclining rather to red. It is made by adding to a solution of ordinary phosphate of soda in excess a solution first of sulphate of zinc and then of sulphate of cobalt, and washing and igniting the precipitate. The result is a vitreous blue with a purple cast, of little body, and exceedingly difficult to grind. Altogether, it is not unlike smalt, over which it has no advantages as an artistic pigment either in colour or permanence. For tinting porcelain, however, it is admirably adapted, imparting thereto a very pure darkblue of extraordinary beauty. This blue is distinguished from smalt by dissolving in acetic acid.Compared with the wide range of yellows, or even with reds, the artist finds the number of his blues limited. The perfect native and excellent artificial ultramarines, the good blues of cobalt, the fair Prussian blue, and the doubtful indigo, are the four varieties he has for years been in the habit of using, and is still mainly dependent on. Our division, therefore, into permanent, semi-stable, and fugitive, is easily effected.In the front rank, pre-eminent among blues as among pigments generally, stands genuine ultramarine. Behind it, are the artificial ultramarines; and behind them again, cobalt and cerulian blue. To a greater or less extent, all these are durable.Among the semi-stable, must be classed cyanine or Leitch's blue, smalt, and Prussian blue.To the fugitive, belong indigo and the somewhat more permanent intense blue, Antwerp blue, and the copper blues.In this list of blues, which grace or disgrace the palette of the present day, there is one colour which, although not permanent, is almost indispensable. As yet, the chemist cannot in all cases lay down the law as to what pigments may or may not be employed. The painter who unnecessarily uses fugitive colours must have little love for his craft, and a poor opinion of the value of his work; but, even with the best intentions and the utmost self-esteem, the artist cannot always confine himself to strictly stable pigments. He has no right to use orpiment instead of cadmium yellow, or red lead instead of vermilion, or copper blue instead of cobalt: he has no business to employ indigo when Prussian blue saddened by black will answer his purpose; but—what pigment can he substitute for Prussian blue itself? None. In its wondrous depth, richness, and transparency, it stands alone: there is no yellow to compare with it, no red to equal it, no blue to rival it. In force and power it is a colour among colours, and transparent beyond them all. The great importance of transparent pigments is to unite with solid or opaque colours of their own hues, giving tone and atmosphere generally, together with beauty and life; to convert primary into secondary, and secondary into tertiary colours, with brilliancy; to deepen and enrich dark colours and shadows, and to impart force and tone to black itself. For such effects, no pigment can vie with Prussian blue. What purples it produces, what greens it gives, what a matchless range of grays; what velvety glow it confers, how it softens the harshness of colours, and how it subdues their glare. No; until the advent of a perfect palette, the artist can scarcelypart with his Prussian blue; nor can the chemist, who has nothing better to offer, hold him to blame. It is for Art to copy Nature with the best materials she possesses: it is for Science to learn the secrets of Nature, and turn them to the benefit of Art.CHAPTER XI.ON THE SECONDARY, ORANGE.Orangeis the first of the secondary colours in relation to light, being in all the variety of its hues composed ofyellowandred. A true or perfect orange is such a compound of red and yellow as will neutralize a perfect blue in equal quantity either of surface or intensity; and the proportions of such compound are five of perfect red to three of perfect yellow. When orange inclines to red, it takes the names ofscarlet,poppy, &c.: in gold colour, &c., it leans towards yellow. Combined with green it forms the tertiarycitrine, and with purple the tertiaryrusset: it also furnishes a series of warm semi-neutral colours with black, and harmonizes in contact and variety of tints with white.Orange is an advancing colour in painting:—in nature it is effective at a great distance, acting powerfully on the eye, diminishing its sensibility in accordance with the strength of the light in which it is viewed. It is of the hue, and partakes of the vividness of sunshine, as it likewise does of all the powers of its components, red and yellow. Pre-eminently awarmcolour, being the equal contrast of or antagonist to blue, to which the attribute ofcoolnesspeculiarly belongs, it is discordant when standing alone with yellow or with red, unresolved by their proper contrasts or harmonizing colours, purple and green. As an archeus or ruling colour, orange is one of the most agreeable keys in toning a picture, from the richness and warmth of its effects. If it predominate therein, for the colouring to be true, the violet and purple should be more or less red, the red more or less scarlet, the yellow more or less intense and orange, and the orange itself be intense and vivid. Further, the greens must lose some of their blue and consequently become yellower, the light blues be more or less light grey, and the deep indigo more or less marrone.Although the secondary colours are capable of being obtained by admixture of the primaries in an infinitude of hues, tints, and shades; yet simple original pigments of whatever class—whether secondary, tertiary, or semi-neutral—are, it has been said before, often superior to those compounded, both in a chemical and artistic sense. Hence a thoroughly good original orange is only of less value and importance than a thoroughly good original yellow, a greenthan a blue, or a purple than a red. To produce pure and permanent compound hues requires practice and knowledge, and we too often see in the works of painters combinations neither pleasing nor stable. Colours are associated with each other which do not mix kindly, and compounds formed of which one or both constituents are fugitive. As a consequence, mixed tints are frequently wanting in clearness, and, where they do not disappear altogether, resolve themselves into some primary colour; orange becoming red by a fading of the yellow, green yellow by a fading of the blue, and purple blue by a fading of the red. Again, with regard to compound tints, there is the danger of one colourreactingupon and injuring another, as in the case of greens obtained from chrome yellow and Prussian blue, where the former ultimately destroys the latter. Of course a mixture of two permanent pigments which do not react on each other will remain permanent; the green, for instance, furnished by aureolin and native ultramarine lasting as long as the ground itself. To produce, however, the effects desired, the artist does not always stop to consider the fitness and stability of his colours in compounding, even if he possess the needed acquaintance with their physical and chemical properties. At all times, therefore, but especially when such knowledge is slight, good orange, &c., pigments are of moreor less value, as by their use the employment of inferior mixtures is to a great extent avoided. In mingling primary with primary, if one colour does not compound well with the other, or is fugacious, the result is failure; but a secondary is not so easily affected by admixture: a green, for example, is seldom quite ruined by the injudicious addition of blue or yellow; and even if either of the latter be fugitive, the green will remain a green if originally durable. Thus the secondaries, if they are not already of the colour required, may be brightened or subdued, deepened or paled, with comparative impunity. The artist who, from long years of experience, knows exactly the properties and capabilities of the colours he employs, may in a measure dispense with secondary pigments, and obtain from the primaries mixed tints at once stable, beautiful, and pure; but even he must sometimes resort to them, as when a green like emerald or viridian is required, which no mixture of blue and yellow will afford. The primaries, by reason of their not being able to be composed of other colours, occupy the first place on the palette, and are of the first importance; but the secondaries are far too useful to be disregarded, and have a value of their own, which both veteran and tyro have cause to acknowledge.The list of original orange pigments was once so deficient, that in some old treatises on thesubject of colours, they are not even mentioned. This may have arisen, not merely from their paucity, but from the unsettled signification of the term orange, as well as from improperly calling these pigments reds, yellows, &c. In these days, however, orange pigments are sufficiently numerous to merit a chapter to themselves; they indeed comprise some of the best colours on the palette.155. BURNT SIENNA,orBurnt Terra di Sienna, is calcined raw Sienna, of a rich transparent brown-orange or orange-russet colour, richer, deeper, and more transparent than the raw earth. It also works and dries better, has in other respects the qualities of its parent colour, and is a most permanent and serviceable pigment in painting generally. For the warm tints in rocks, mud banks, and buildings, this colour is excellent. When mixed with blue it makes a good green; furnishing a bright green with cobalt, and one much more intense with Prussian blue. For the foresea, whether calm or broken by waves, it may be employed with a little madder; while compounded with a small portion of the latter and lamp black, it meets the hues of old posts, boats, and a variety of near objects, as the tints may be varied by modifying the proportions of the component colours. Used with white, it yields a range ofsunny tones; and with aureolin or French blue and aureolin will be found of service, the last compound giving a fine olive green. Similar but fugitive greens are afforded by admixture of burnt Sienna with indigo and yellow or Roman ochre, or raw Sienna; tints which may be saddened into olive neutrals by the addition of sepia, and rendered more durable by substituting for indigo Prussian blue and black. Mixed with viridian, it furnishes autumnal hues of the utmost richness, beauty, and permanence; and, alone, is valuable as a glaze over foliage and herbage. For the dark markings and divisions of stones a compound of Payne's gray and burnt Sienna will prove serviceable; while for red sails the Sienna, either by itself, with brown madder, or with Indian red, cannot be surpassed. For foregrounds, banks and roads, cattle and animals in general, burnt Sienna is equally eligible, both alone and compounded. It has a slight tendency to darken by time.156. CADMIUM ORANGEwas first introduced to the art-world at the InternationalExhibitionof 18621862, where it was universally admired for its extreme brilliancy and beauty, a brilliancy equalled by few of the colours with which it was associated, and a beauty devoid of coarseness. We remember well the power it possessed of attracting the eye from a distance;and how, on near approach, it threw nearly all other pigments into the shade. It has in truth a lustrous luminosity not often to be met with, added to a total absence of rankness or harshness. A simple original colour, containing no base but cadmium, it is of perfect permanence, being uninjured by exposure to light, air or damp, by sulphuretted hydrogen, or by admixture. Having in common with cadmium sulphides a certain amount of transparency, it is invaluable for gorgeous sunsets and the like, either alone or compounded with aureolin. Of great depth and power in its full touches, the pale washes are marked by that clearness and delicacy which are so essential in painting skies. As day declines, and blue melts into green, green into orange, and orange into purple, the proper use of this pigment will produce effects both glowing and transparent. Transparency signifies the quality of being seen through or into; and in no better way can it be arrived at than by giving a number of thin washes of determined character, each lighter than the preceding one. With due care in preserving their forms, from the commencement to the termination, such washes of orange will furnish hues the softest and most aerial. For bits of bright drapery, a glaze over autumn leaves, and mural decoration, this colour is adapted; while in illumination it supplies a want formerly much felt. "Withthe exception of scarlet or bright orange," said Mr. Bradley, nine or ten years since, in his Manual of Illumination, "our colours are everything we could wish." As an original pigment, a permanent scarlet does not yet exist; but the brilliancy of cadmium orange cannot be disputed, nor its claim to be the only unexceptionable bright orange known. It even assists the formation of the other colour: remarks the author mentioned, "Brilliancy is obtained by gradation. Suppose a scarlet over-curling leaf, for example. The whole should be painted in pure orange, with the gentlest possible after-touch of vermilion towards the corner under the curl. When dry, a firm line—not wash—of carmine, (of madder, preferable.—Ed.), passed within the outline on the shade side only of the leaf, will give to the whole the look of a bright scarlet surface, but with an indescribable superadded charm, that no merely flat colour can possess." In the same branch of art, illumination, cadmium orange, opposed to viridian, presents a most dazzling contrast, especially if relieved by purple.157. CHINESE ORANGEbelongs to the coal-tar colours, and ought strictly to have been classed therewith. We have preferred, however, to keep it separate, because, as Chinese Orange, it was introduced as a pigment,and has not been employed as a dye. In colour, it somewhat resembles burnt Sienna, enriched, reddened, brightened, and made more transparent, by admixture with crimson lake. From its behaviour, it would seem to be composed of yellow and red, such a compound as magenta and aniline yellow would afford. Its pale washes are uncertain, being apt to resolve themselves into red and yellow, of which the latter appears the most permanent; for, on exposure to light and air, the red more or less flies, leaving here a yellow, and there a reddish-yellow ground: in places both red and yellow disappear. Like all fugitive colours, it is comparatively stable when used in body; but even then it entirely loses its depth and richness, and in a great measure its redness, becoming faded and yellowish. In thin washes or glazing it is totally inadmissible; and, being neither a red, an orange, nor a brown, is unsuited to pure effects. Nevertheless, where it need not be unduly exposed; in portfolio illuminations, for instance, the richness, subdued brilliancy, and transparency of this pigment, justify its adoption. It is not affected by an impure atmosphere.Aniline colours may be adapted for oil painting by dissolving them in the strongest alcohol, saturating the solution with Dammar resin, filtering the tincture, and pouring the filtrate either on pure water or solution of common salt, stirring well allthe time. The water or brine solution must be at least twenty times the bulk of the tincture. The colour after being collected on a filter, washed, and dried, can be ground with linseed oil, poppy oil, or oil varnishes.158. CHROME ORANGE,Orange Chrome, orOrange Chromate of Lead, is a sub-chromate of lead of an orange-yellow colour, produced by the action of an alkali on chrome yellow. Like all the chromates of lead, it is characterized by power and brilliancy; but also by a rankness of tone, a want of permanence, and a tendency to injure organic pigments. By reason of its lead base it is subject to alteration by impure air, but is on the whole preferable to the chrome yellows, being liable in a somewhat less degree to their changes and affinities. As, however, a colour has no business to be used if a better can be procured, the recent introduction of cadmium orange renders all risk unnecessary.159. MARS ORANGE,Orange de Mars, is a subdued orange of the burnt Sienna class, but without the brown tinge that distinguishes the latter. Marked by a special clearness and purity of tone, with much transparency, it affords bright sunny tints in its pale washes, and combines effectively with white.Being an artificial iron ochre it is more chemically active than native ochres, and needs to be cautiously employed with pigments affected by iron, such as the lakes of cochineal and intense blue.160. MIXED ORANGE.Orange being a compound colour, the place of original orange pigments can be supplied by mixtures of yellow and red; either by glazing one over the other, by stippling, or by other modes of breaking and intermixing them, according to the nature of the work and the effect required. For reasons lately given, mixed pigments are apt to be inferior to the simple or homogeneous both in colour, working, and other properties; yet some pigments mix and combine more cordially and with better results than others; as is the case with liquid rubiate and gamboge. Generally speaking, the compounding of colours is easier in oil than in water; but in both vehicles trouble will be saved by beginning with the predominating colour, and adding the other or others to it.Perhaps in this, our first chapter on the secondary colours, and consequently on colours that can be compounded, a few remarks on mixed tints from a chemical point of view will not be deemed superfluous.There are two ways, we take it, of looking ata picture—from a purely chemical, and from a purely artistic, point of view. Regarded in the first light, it matters little whether a painting be a work of genius or a daub, provided the pigments employed on it are good and properly compounded. The effects produced are lost sight of in a consideration of the materials, their permanence, fugacity, and conduct towards each other. Painting is essentially a chemical operation: with his pigments for reagents, the artist unwittingly performs reaction after reaction, not with the immediate results indeed of the chemist in his laboratory, but often as surely. As colour is added to colour, and mixture to mixture, acid meets alkali, metal animal, mineral vegetable, inorganic organic. With so close a union of opposite and opposing elements, the wonder is not so much that pictures sometimes perish, but that they ever live. It behoves the artist, then, not only to procure the best and most permanent pigments possible, but to compound them in such a manner that his mixed tints may be durable as well as beautiful. To effect or aid in effecting this, although he may not always be able to act upon them, the following axioms should be borne in mind:—If they do not react on each other, a permanent pigment added to a permanent pigment yields a permanent mixture.If they do react on each other, a permanentpigment added to a permanent pigment yields a semi-stable or fugitive mixture.A permanent pigment added to a semi-stable pigment yields a semi-stable mixture.A permanent pigment added to a fugitive pigment yields a fugitive mixture.Consequently—A permanent pigment may be rendered fugitive or semi-stable by improper compounding.A semi-stable or fugitive pigment is not rendered durable by being compounded.As a chain is only as strong as its weakest link, so a mixture is only as permanent as its least durable constituent.To give illustrations—Ultramarine added to Chinese white yields a permanent mixture.Ultramarine added to an acid constant white yields a semi-stable or fugitive mixture.Ultramarine added to Prussian blue yields a semi-stable mixture.Ultramarine added to indigo yields a fugitive mixture.Except in the second instance, where the blue is either partially or wholly destroyed—in time, be it remembered, not at once—according to the quantity and strength of the acid in the white, the ultramarine remains unchanged. Hence at first sight our third and fourth conclusions mayappear wrong; inasmuch as, it may be argued, a blue mixture cannot be semi-stable or fugitive when blue is left. To this we reply, unless both constituents are fugitive, a mixture will always more or less possess colour; but, if even one constituent be semi-stable or fugitive, a mixture will slowly but surely losethecolour for which it was compounded, and beas a mixturesemi-stable or fugitive.It need hardly be observed that the number of permanent orange, green, and purple hues which the artist can compound, depends mainly on the number of permanent yellows, reds, and blues at his disposal. In mixed orange, therefore, a selection of durable yellows and reds is of the first importance. It should, however, be remarked that mixed orange, more sober and less decided, is obtainable by the use of citrine and russet; in the former of which yellow predominates, and in the latter, red: consequently orange results when yellow is added to russet, red to citrine, or citrine to russet.PERMANENT YELLOWS.PERMANENT REDS.Aureolin.Cadmium Red.Cadmium, deep.Liquid Rubiate.Cadmium, pale.Madder Carmine.Lemon Yellow.Rose Madder.Mars Yellow.Mars Red.Naples Yellow, modern.Ochres.Ochres.Vermilions.Orient Yellow.Raw Sienna.None of these pigments react on each other, and from them can be produced the most durable mixed orange that yellow and red will afford.161. NEUTRAL ORANGE,orPenley's Neutral Orange, is a permanent compound pigment composed of yellow ochre and the russet-marrone known as brown madder: it is chiefly valuable in water-colour. Paper, being white, is too opaque to paint upon, without some wash of colour being first passed over it; otherwise the light tones of the sky are apt to look crude and harsh. It must, therefore, be gone over with some desirable tint, that shall break, in a slight degree, the extreme brilliancy of the mere paper. For this purpose, a thin wash of the orange is to be put over the whole surface of the paper with a large flat brush, care being taken never to drive the colour too bare,i.e.never to empty the brush too closely, but always to replenish before more is actually required. This first wash of colour not only gives a tone to the paper, but secures the pencil sketch from being rubbed out.The reason why, in this compound, yellow ochre, as a yellow, is preferred to any of the others, is, that it is a broken yellow, that is, a yellow slightly altered by having another hue, such as red, or brown, in its composition. It is somewhat opaque too, and hence, from thisquality, is especially adapted for distances. Brown madder also is a subdued red, which, when in combination with the former, produces a neutral orange, partaking of the character of soft light. As a general rule, yellow ochre is to predominate in broad daylight, and brown madder in that which is more sombre and imperfect: hence the pigment can be yellowed or reddened, by the addition of one or the other. For a clear sunset, the neutral orange must be repeated, with a preponderance of ochre at the top, assisted by a little cadmium yellow near the sun; the madder being added downwards.In treating of distant mountains, a distinction is to be made between them and the clouds, the former requiring solidity, while the latter are only to be regarded as vapour and air. Mountains, being opaque bodies, are acted upon by atmosphere more or less, according to their position, their distance, and the state of the weather. To express this distinction, recourse must be had to an under tint, except where the tone is decidedly blue—an uncommon case. No mixture can give this with such truth as the neutral orange. A wash, therefore, should be passed over the mountains, with nearly all yellow in the high lights, or in the gleams of sunshine, and, on the contrary, almost all brown madder for the shadows. These two degrees of tone must be run into each otherwhile the drawing is wet. A beautiful and soft under tone will thus be given to receive the greys.162. ORANGE, OR BURNT ROMAN OCHRE,called alsoSpanish Ochre, is a very bright yellow or Roman ochre burnt, by which operation it acquires warmth, colour, transparency, and depth. Moderately bright, it forms good flesh tints with white, dries and works well both in water and oil, and is a very good and eligible pigment. It may be used in enamel painting, and has all the properties of its original ochre in other respects.A redder hue is imparted by mixing the ochre with powdered nitre before ignition, the orange red being subsequently washed with hot water.163.Anotta,Annotto, Annatto, Arnotto, Arnotta, Terra Orellana, Rocou, &c., is met with in commerce under the names of cake anotta, and flag or roll anotta. The former, which comes almost exclusively from Cayenne, should be of a bright yellow colour: the latter, which is imported from the Brazils, is brown outside and red within. It is prepared from the pods of thebixa orellana, and appears generally to contain two colouring matters, a yellow and a red, which are apt to adhere to each other and produce orange. Anottadissolves with difficulty in water, but readily in alcohol and alkaline solutions, from which last it may be thrown down as a lake by means of alum. Being, however, exceedingly fugitive and changeable, it is not fit for painting; but is chiefly employed in dyeing silk, and colouring varnishes and cheese. Very red cheese should be looked upon with suspicion, for although the admixture of anotta is in no way detrimental to health provided the drug be pure, it is commonly adulterated with red lead and ochre. Several instances are on record that Gloucester and other cheeses have been found contaminated with red lead, through having been coloured with anotta containing it, and that this contamination has produced serious consequences.Bixineis a purified extract of anotta made in France, and used by dyers.164.Antimony Orange,Golden Sulphur of Antimony, or Golden Yellow, is a hydro-sulphuret of antimony of an orange colour, which is destroyed by the action of strong light. It is a bad dryer in oil, injurious to many pigments, and in no respect eligible either in water or oil.165.Chromate of Mercuryhas been improperly classed as a red with vermilion, for though it is of a bright ochrous redin powder, when ground it becomes a bright ochre-orange, and affords with white very pure orange tints. Nevertheless it is a bad pigment, since light soon changes it to a deep russet colour, and foul air reduces it to extreme blackness.166.Damonico,or Monicon, is an iron ochre, being a compound of raw Sienna and Roman ochre burnt, and having all their qualities. It is rather more russet in hue than the pigment known as orange or burnt Roman ochre, has considerable transparency, is rich and durable in colour, and furnishes good flesh tints. As in orange ochre, powdered nitre may be employed in its preparation. Notwithstanding its merits, it is obsolete or nearly so; doubtless because burnt Sienna mixed with burnt Roman ochre sufficiently answers the purpose.167.Gamboge Orange.On adding acetate of lead to a potash solution of gamboge, a rich bright orange is precipitated, which may be washed on a filter till the washings are colourless, and preserves its hue with careful drying. The orange which we thus obtained stood well in a book, but it cannot be recommended as an artistic pigment. Perhaps in dyeing, the lead and gamboge solutions might be worth a trial.168.Laque Minéraleis a French pigment, a species of chromic orange, similar to the orange chromate of lead. This name is likewise given to orange oxide of iron.169.Madder Orange,or Orange Lake. It has been said that the yellows so-called produced from madder are not remarkable for stability, differing therein from the reds, purples, russets, and browns. Like them, this 'orange' is of doubtful colour and permanence, and not to be met with, brilliant and pure, on the palette of to-day. The russet known as Rubens' madder has a tendency to orange.170.Orange Lead,of a dull orange colour, is an orange protoxide of lead or massicot. Like litharge, it may be employed in the preparation of drying oils, and, being a better drier than white lead, may be substituted for it in mixing with pigments which need a siccative, as the bituminous earths.Minium sometimes leans to orange; and there is made from ceruse a peculiar red,Mineral Orange.Orange Orpiment,or Realgar, has also been called Red Orpiment,improperly, since it is a brilliant orange, inclining to yellow. There are two kinds, a native and an artificial, of which the former is thesandaracof the ancients, and is rather redder than the latter. They possess the same qualities as pigments, and as such resemble yellow orpiment, to which the old painters gave the orange hue by heat, naming it alchemy and burnt orpiment. Orange orpiment contains more arsenic and less sulphur than the yellow, and is of course highly poisonous. It is often sophisticated with brickdust and yellow ochre.172.Thallium Orangeis produced when bichromate of potash is added to a neutral salt of the protoxide of thallium, as an orange-yellow precipitate. The scarcity of the metal precludes their present introduction as pigments, but if the chromates of thallium were found to resist the action of light and air, and not to become green by deoxidation of the chromic acid, they might possibly prove fitted for the palette. It is a question whether theirveryslight solubility in water would be a fatal objection; and, although they would be liable to suffer from a foul atmosphere, we are inclined to think the effects would not be so lasting as in the chromates of lead. Like lead sulphide, the sulphide of thallium ranges from brown to brownish-black, or grey-black; and, like it too,is subject to oxidation and consequent conversion into colourless sulphate. It is, however, much more readily oxidized than sulphate of lead; and hence the thallium chromates would doubtless soon regain their former hue on exposure to a strong light.Mr. Crookes, who discovered this new metal in 1861, believes that the deep orange shade observable in some specimens of sulphide of cadmium is due to the presence of thallium. He has frequently found it, he says, in the dark-coloured varieties, and considers the variations of colour in cadmium sulphide to be owing to traces of thallium. That thallium affects the colour is most probable, but it is not necessarily the cause of the orange hue. The tint of cadmium sulphide is a mere matter of manufacture, seeing that from the same sample of metal there can be obtained lemon-yellow, pale yellow, deep yellow, orange-yellow, and orange-red. With deference to the opinion of a chemist so distinguished, we hold that thallium rather impairs the beauty of cadmium sulphide than imparts to it an orange shade, the thallium being likewise in the form of sulphide, and therefore more or less black. On chromate of cadmium, made with bichromate of potash, thallium would naturally confer an orange hue.173.Uranium Orangeis obtainable by wet and dry methods as ayellowish-red, or, when reduced to powder, an orange-yellow, uranate of baryta. It is an expensive preparation, superfluous as a pigment.174.Zinc Orange.When hydrochloric acid and zinc are made to act on nitro-prusside of sodium, a corresponding zinc compound is formed of a deep orange colour, slightly soluble in water, and not permanent.For a secondary colour, orange is well represented on the modern palette, and can point to some pigments as good and durable as any to be found among the primaries. Burnt Sienna, cadmium orange, Mars orange, neutral orange, and orange or burnt Roman ochre, are all strictly permanent. The so-called orange vermilions were, it will be remembered, classed among the reds.As semi-stable, must be ranked chrome orange; and as fugitive, Chinese orange, orange orpiment, and orange lead.From the foregoing division, the predominance of eligible orange pigments over those less trustworthy is manifest. Unfortunately, with many painters it is not so manifest that their secondary and compound colours should receive as much attention as the primaries, and that it is their duty, not only to the art which they practice, but to the patrons for whom they practiceit, that their orange and green and purple hues, should be as durable as their yellows, reds, and blues. For such, the introduction of a new permanent pigment is of little interest, unless its colour be primary; so wedded are they to that passion for compounding which the chemist views with dismay. With dismay, because he knows that the rules of mixture are severe, and cannot with impunity be altered; that, although disguised in oil or gum, each pigment is a chemical compound, with more or less of affinity and power, more or less likely to act or be acted upon. Because he knows that, except with the most experienced artists, compounding leads to confusion; and that in it the temptations to use semi-stable or fugitive colours are strong. Look at those tables of mixed tints of which artist-authors are so fond, and tell us whether they always bear scrutiny—surely not. Admirable, perfect as these tints may be in an artistic sense, how often is their beauty like the hectic flush of consumption, which carries with it the seeds of a certain death. Will that orange where Indian yellow figures ever see old age, or that green with indigo, or purple with cochineal lake? Will they not rather spread over the picture the Upas-tree of fugacity, and kill it as they die themselves!CHAPTER XII.ON THE SECONDARY, GREEN.Green, which occupies the middle station in the natural scale of colours and in relation to light and shade, is the second of the secondary colours. It is composed of the extreme primaries,yellowandblue, and is most perfect in hue when constituted in the proportions of three of yellow to eight of blue of equal intensities; because such a green will exactly neutralize and contrast a perfect red in the ratio of eleven to five, either of space or power. Of all compound colours, green is the most effective, distinct, and striking, causing surprise and delight when first produced by a mixture of blue and yellow, so dissimilar to its constituents does it appear to the untutored eye. Compounded with orange, green converts it into the one extreme tertiarycitrine; while mixed with purple, it becomes the other extreme tertiaryolive: hence its relations and accordances are more general, and its contrasts more agreeable with all colours, than those of any other individualcolour. Accordingly it has been adopted very wisely in nature as the common garb of the vegetal creation. It is, indeed, in every respect a central or medial colour, being the contrast, compensatory in the proportion of eleven to five, of the middle primaryred, on the one hand, and of the middle tertiaryrusset, on the other; while, unlike the other secondaries, all its hues, whether tending to blue or yellow, are of the same denomination.These attributes of green, which render it so universally effective in contrasting colours, cause it also to become the least useful in compounding them, and the most apt to defile other colours in mixture. Nevertheless it forms valuable semi-neutrals of the olive class withblack, for of such subdued tones are those greens by which the more vivid tints of nature are opposed. Accordingly, the various greens of foliage are always more or less semi-neutral in hue. As green is the most general colour of vegetal nature and principal in foliage; so red, its harmonizing colour, with compounds of red, is most general and principal in flowers. Purple flowers are commonly contrasted with centres or variegations of bright yellow, as blue flowers are with like relievings of orange; and there is a prevailing hue, or character, in the green colour of the foliage of almost every plant, by which it is harmonized with the colours of its flowers.The chief discord of green is blue; and when they approximate or accompany each other, they require to be resolved by the opposition of warm colours. It is in this way that the warmth of distance and the horizon reconciles the azure of the sky with the greenness of a landscape. Its less powerful discord is yellow, which needs to be similarly resolved by a purple-red, or its principles. In tone, green is cool or warm, sedate or gay, either as it inclines to blue or to yellow; yet in its general effects it is cool, calm, temperate, and refreshing. Having little power in reflecting light, it is a retiring colour, and readily subdued by distance: for the same reason, it excites the retina less than most colours, and is cool and grateful to the eye. As a colour individually, green is eminently beautiful and agreeable, but it is more particularly so when contrasted by its compensating colour, red, as it often is in nature, even in the green leaves and young shoots of plants and trees. "The autumn only is called the painter's season," remarks Constable, "from the great richness of the colours of the dead and decaying foliage, and the peculiar tone and beauty of the skies; but the spring has, perhaps, more than an equal claim to his notice and admiration, and from causes not wholly dissimilar,—the great variety of tints and colours of the living foliage, accompanied by their flowers and blossoms. Thebeautiful and tender hues of the young leaves and buds are rendered more lovely by being contrasted, as they now are, with the sober russet browns of the stems from which they shoot, and which still show the drear remains of the season that is past."The number of pigments of any colour is in general proportioned to its importance; hence the variety of greens is very great, though the classes of those in common use are not very numerous. Of the three secondaries, green is the colour most often met with, and, consequently, the most often compounded: for this last reason, perhaps, the palette is somewhat deficient in really good original greens—more deficient than there is any necessity for.CHROME OXIDES.By numerous methods both wet and dry, oxides of chromium are obtainable pale and deep, bright and subdued, warm and cool, opaque and transparent: sometimes hydrated, in which case they cannot be employed in enamelling; and sometimes anhydrous, when they are admissible therein. But whatever their properties may be, chemical, physical, or artistic, they are all strictly stable. Neither giving nor receiving injury by admixture, equally unaffected by foul gas and exposure to light, air, or damp, these oxides are perfectly unexceptionable in every respect.For the most part they are eligible in water and oil, drying well in the latter vehicle, and requiring in the former much gum. They have long been known as affording pure, natural, and durable tints; but, until within the last few years, have been rather fine than brilliant greens. Lately, however, processes have been devised, yielding them almost as bright, rich, and transparent, as the carmine of cochineal itself.175. OXIDE OF CHROMIUM,Opaque Oxide of Chromium,Green Oxide of Chromium,Chrome Oxide,True Chrome Green,Native Green,&c., is found native in an impure state as Chrome Ochre, but is always artificially prepared for artistic use. Obtained anhydrous by dry modes, this is the only chrome oxide available in enamelling, and is the one seen on superior porcelain. It is a cold, sober sage green, deep-toned, opaque, and, although dull, agreeable to the eye. Its tints with white are peculiarly delicate and pleasing, possessing a silvery luminous quality, and giving the effect of atmosphere. Being very dense and powerful, it must be employed with care to avoid heaviness, and is preferably diluted with a large quantity of white, or compounded with transparent yellow. In the hands of a master, this gray-green furnishes lustrous hues with brown pink, Italian pink, and Indian yellow; three beautiful butfugitive pigments, of which the two last may be replaced by aureolin. Of this Mr. Penley observes, "as adapted for the colouring of foliage and herbage, it is impossible to say too much in its praise. It imparts the vividness and freshness of nature to every colour with which it is combined;" and he brackets oxide of chromium with aureolin as a compound hue "extremely useful." In flat tints, the oxide sometimes does not wash well in water.176. TRANSPARENT OXIDE OF CHROMIUMbeing deficient in body, is only eligible in oil. A very pale greyish-white green in powder, it gives an agreeable yellowish green of some depth in oil, moderately bright, but not very pure or clear.We are acquainted with another transparent chrome oxide of far greater beauty, brightness, purity, and clearness than the above. Of a bluish green hue, a difficulty in getting it to mix with oil renders it at present unavailable.177. VERONESE GREEN,orFrench Veronese Green, is a comparatively recent introduction, similar in colour and general properties to the following; beside which, however, it appears dull, muddy, and impure. It is often adulterated with arsenic to an enormous extent, which interferes with its transparency,mars its beauty, and renders it of course rankly poisonous.178. VIRIDIANis a still later addition to the palette, and the only permanent green which can be described as gorgeous, being not unlike the richest velvet. Pure and clear as the emerald, it may be called the Prussian Blue of Greens, of such richness, depth, and transparency is it. In hue of a bluish-green, its deepest shades verge on black, while its light tints are marked by transparent clearness unsurpassed. No compound of blue and yellow will afford a green at once so beautiful and stable, so gifted with the quality of light, and therefore so suited for aerial and liquid effects. Used with aureolin, it gives foliage greens sparkling with sunshine; and, fitly compounded, will be found invaluable for the glassy liquidity of seas, in painting which it becomes incumbent to employ pigments more or less transparent. "The general failing in the representation of the sea is, that instead of appearing liquid and thin, it is made to bear the semblance of opacity and solidity. In order to convey the idea of transparency, some object is often placed floating on the wave, so as to give reflection; and it is strange that we find our greatest men having recourse to this stratagem. To say it is not true in all cases, is saying too much; but this we doassert, that as a general principle it is quite false, and we prove it in this way: water has its motion, more or less, from the power of the wind; it is acted upon in the mass, and thus divided into separate waves, and these individually have their surface ruffled, which renders them incapable of receiving reflection. The exception to this will be, where the heaving of the sea is the result of some gone-by storm, when the wind is hushed, and the surface becomes bright and glassy. In this state, reflections are distinctly seen. Another exception will be in the hollow portion of the waves, as they curl over, and dash upon the shore."As viridian, like the sea, is naturally "liquid and thin, bright and glassy," the extract we have quoted from Mr. Penley, points to this green as a pigment peculiarly adapted for marine painting; in which, it may be added, its perfect permanence and transparency will be appreciated in glazing. Its fitness for foliage has been remarked; but in draperies the colour will prove equally useful, and in illumination will be found unrivalled. In the last branch of art, indeed, viridian stands alone, not only through its soft rich brilliancy, but by the glowing contrast it presents with other colours: employed as a ground, it throws up the reds, &c., opposed to it, in a marvellous manner. Like the three preceding oxides of chromium, viridian neither injures noris injured by other pigments; is unaffected by light, damp, or impure air; and is admissible in fresco. In enamelling it cannot be used; the colour, depending on the water of hydration, being destroyed by a strong heat.COPPER GREENSare commercially known asEmerald Green,Malachite Green,Scheele's Green,Schweinfurt Green,Verdigris,Green Bice,Green Verditer,Brunswick Green,Vienna Green,Hungary Green,Green Lake,Mineral Green,Patent Green,Mountain Green,Marine Green,Saxon Green,French Green,African Green,Persian Green,Swedish Green,Olympian Green,Imperial Green,Mitis Green,Pickle Green, &c.The general characteristics of these greens are brightness of colour, well suited to the purposes of house-painting, but seldom adapted to the modesty of nature in fine art; considerable permanence, except when exposed to the action of damp and impure air, which ultimately blacken most of them; and good body. They have a tendency to darken by time, dry well as a rule in oil, and are all more or less poisonous, even those not containing arsenic.179. EMERALD GREEN,Schweinfurt Green,Vienna Green,Imperial Green,Brunswick Green,Mitis Green, &c., is a cupric aceto-arsenite, prepared on the large scale bymixing arsenious acid with acetate of copper and water. It differs from Scheele's Green, or cupric arsenite, in being lighter, more vivid, and more opaque. Powerfully reflective of light, it is perhaps the most durable pigment of its class, not sensibly affected by damp nor by that amount of impure air to which pictures are usually subject: indeed it may be ranked as permanent both in itself and when in tint with white. It works better in water than in oil, in which latter vehicle it dries with difficulty. Bearing the same relation to greens generally as Pure Scarlet bears to reds, its vivid hue is almost beyond the scale of other bright pigments, and immediately attracts the eye to any part of a painting in which it may be employed. Too violent in colour to be of much service, it has the effect, when properly placed, of toning down at once, by force of contrast, all the other greens in a picture. If discreetly used, it is occasionally of value in the drapery of a foreground figure, where a bright green may be demanded; or in a touch on a gaily painted boat or barge. When required, no mixture will serve as a substitute. Compounded with aureolin, it becomes softened and semi-transparent, yielding spring tints of extreme brilliancy and beauty.180. SCHEELE'S GREEN,orSwedish Green, resembles the preceding varietyin being a compound of copper and arsenic, and therefore rankly poisonous; but differs from it in containing no acetic acid, in possessing less opacity, and in having a darker shade. It is a cupric arsenite, with the common attributes of emerald green, under which name it is sometimes sold. Of similar stability, it must not be employed with the true Naples yellow or antimoniate of lead, by which it is soon destroyed.Upon the lavish use of this dangerous pigment in colouring toys, dresses, paper-hangings, artificial leaves, and even cheap confectionery, it is not our province to enlarge: the constant-recurring diseases and deaths, which, directly or indirectly, result from the employment of arsenical pigments, are such every-day facts that they are merely deplored and forgotten. With arsenic on our heads, our clothes, our papers, our sweets, ourchildren'splaythings, we are so accustomed to live—and die—in a world of poison, that familiarity with it has bred contempt. Into the fatal popularity, therefore, of arsenical colours for decorative purposes, we shall not further enter; but it behoves us to deprecate their presence, and the presence of all poisonous pigments, in colour-boxes for the young. It is one of the pleasures of childhood to suck anything attractive that comes in its way, openly if allowed, furtively otherwise: and as in early life we have a preference for brilliancy, so vivid a pigment asScheele's green is an object of special attention. Artistically, it matters little whether a pigment is noxious or not, but we hold that poison should not be put into the hands of the young; and indeed are of opinion that a box of colours is about the worst present a child can receive.181. MALACHITE GREEN,orMountain Green, is met with in Cumberland, and is also found in the mountains of Kernhausen, whence it is sometimes calledHungary Green. It is prepared from malachite, a beautiful copper ore employed by jewellers, and is a hydrated dicarbonate of copper, combined with a white earth, and often striated with veins of mountain blue, to which it bears the same relation that green verditer bears to blue verditer. The colour, which may be extracted from the stone by the process followed for native ultramarine, varies from emerald-green to grass-green, and inclines to grey. It has been held in great esteem by some, and considered strictly stable, on the assumption, probably, that a pigment obtained from a stone like ultramarine, and by the same method, could not be otherwise than permanent. That it is so, with respect to light and air, there is no denying; but the green, when separated from the ore and purified for artistic use, is merely a carbonate of copper, and therefore subject to the influence of damp and impure air, in common with other non-arsenical copper colours. As a pigment, native malachite green has the same composition, or very nearly the same, as that which can be artificially produced, and answers to the same tests. Water-rubs of the two varieties which we exposed to an atmosphere of sulphuretted hydrogen became equally blackened by the gas. Practically, there is little or no difference between them: both preserve their colour if kept from damp and foul air, both are injured by those agents, and both are liable to darken in time, especially when secluded from light. The artificial, however, can be obtained of a much finer colour than the natural, which it may be made to resemble by admixture with mineral gray. On the whole, they can scarcely be recommended for the palette, and are certainly inferior in durability to Scheele's and Schweinfurt greens. In fresco painting they have been pronounced admissible; but, apart from the question of damp, we should deem the conjunction of lime with carbonate of copper not favourable to permanence. By the action of alkalies, even the native green malachite may be converted into blue; and it becomes a question whether the dingy greenish-blue on some ancient monuments was not originally malachite green.182. VERDIGRIS,orViride Æris, is of two kinds, common or impure, and crystallized orDistilled Verdigris, or, more properly, refined verdigris. The best is made at Montpellier in France, and is a sub-acetate of copper of a bright green colour inclining to blue. The least durable of the copper greens, it soon fades as a water-colour by the action of light, &c., and becomes first white and ultimately black by damp and foul gas. In oil, verdigris is permanent with respect to light and air, but moisture and an impure atmosphere change its colour, and cause it to effloresce or rise to the surface through the oil. It dries rapidly, and is exceptionally useful with other greens or very dark colours. In varnish it stands better; but cannot be considered safe or eligible, either alone or compounded. Vinegar dissolves it, forming a solution used for tinting maps, and formerly much employed for colouring pickles, &c.The painters, who lived at the time when the arts were restored in Italy, used this pigment; and the bright greens seen in some old pictures are made by glazings of verdigris. It is often largely adulterated with chalk and sulphate of copper.183. MIXED GREENGreen, being a compound of blue and yellow, may be got by combining those colours in the several ways of working—by mixing, glazing, hatching, or otherwise blending them in the proportions of the various hues required. To obtain apuregreen, which consists of blue and yellow only, a blue should be chosen tinged with yellow rather than with red, and a yellow tinged with blue. If either a blue or a yellow were taken, tinged with red, this latter colour would go to produce some grey in the compound, which would tarnish the green. The fine nature-like greens, which have lasted so well in some of the pictures of the Italian schools, appear to have been compounded of ultramarine, or ultramarine ashes and yellow. Whatever pigments are employed on a painting in the warm yellow hues of the foreground, and blue colouring of the distance and sky, are advantageous for forming the greens in landscape, &c., because they harmonize better both in colouring and chemically, and impart homogeneity to the whole: a principle conducive to a fine tone and durability of effect, and applicable to all mixed tints. In compounding colours, it is desirable not only that they should agree chemically, but that they should have, as far as possible, the same degree of durability. In these respects, aureolin and ultramarine, gamboge and Prussian blue, Indian yellow and indigo, are all judicious mixtures, although not all to be recommended.PERMANENT YELLOWS.PERMANENT BLUES.Aureolin.Cerulian Blue.Cadmium Yellow, pale.Cobalt Blue.Cadmium Yellow, deep.Genuine Ultramarine.Lemon Yellow.Brilliant Ultramarine.Mars Yellow.French Ultramarine.Naples Yellow, modern.New Blue.Ochres.Permanent Blue.Orient Yellow.Raw Sienna.The foregoing yellows and blues are in no wise inimical to each other, and yield the best mixed greens, chemically considered, the palette can afford. In an artistic sense, we confess, the result is not so satisfactory: the list of blues, it must be admitted, being somewhat scant. Among the latter there is no pigment with the wonderful depth, richness, and transparency of Prussian blue, and none consequently which will furnish with yellow a green of similar quality. That the artist, therefore, will dispense with Prussian blue, it would be too much to expect. There is, however, less necessity for it since the introduction of viridian, a green resembling that which is produced by admixture of Prussian blue and yellow, and which may be varied in hue by being compounded with aureolin or ultramarine. Our object in this work is to give precedence tothe chemical rather than the artistic properties of pigments, to separate the strictly stable from the semi-stable, and the semi-stable from the fugitive. A colour or a mixture may be chemically bad but artistically good, and vice versâ; but the chemist looks upon no pigment or compound with favour unless it be perfectly permanent, and ignores its mere beauty when void of durability. Hence, all artistic considerations are set aside in our lists of permanent pigments: if it be possible to use them alone, so much the better for the permanence of painting; if not, so much the worse will it be, according to the degree of fugacity of the colours employed.184. BRONZE,and the three succeeding varieties, are greens resembling each other in being semi-stable, and more or less transparent. Bronze is a species of Prussian green, of a dull blue-black hue. In its deep washes it appears a greenish-black with a coppery cast. It is used in ornamental work, and sometimes as a background tint for flower pieces.185. CHROME GREENS,commonly so called, are compounds of chromate of lead and Prussian blue, a mixture which is also known asBrunswick Green. Fine bright greens, they are suited to the ordinary purposesof mechanic painting, but are quite unfit for the artist's craft, chrome yellow reacting upon and ultimately destroying Prussian blue when mixed therewith. For the latter, cheap cobalts and ultramarines are preferably substituted, although they do not yield greens of like power and intensity.Under the names of English Green, Green Cinnabar, &c., 'new' green pigments have been from time to time introduced, which have turned out mixtures of Prussian blue and chromate of lead; not made, however, by compounding the two, but directly by processes similar to the following:—A mixed solution of the acetates of lead and iron is added to a mixed solution of the yellow prussiate and chromate of potash, the necessary acetate of iron being obtained by precipitating a solution of acetate of lead by sulphate of iron, and filtering the supernatant liquid. Or; to a solution of Prussian blue in oxalic acid, first chromate of potash is added, and then acetate of lead.By the last process, superior and more permanent chrome greens may be produced, free from lead, by using chloride of barium or nitrate of bismuth in place of the acetate of lead. Chromate of baryta, or chromate of bismuth is then formed, neither of which acts on the Prussian blue.It should be added that where the latter pigment is present, no green will serve for painting walls containing lime, as its action alters the tint of the Prussian blue.186. HOOKER'S GREENis a compound of Prussian blue and gamboge, two pigments possessing a like degree of stability, and perfectly innocuous to each other. It is a mixture more durable and more transparent than chrome greens made with chromate of lead. There are two varieties in common use—No. 11, a light grass green, in which the yellow predominates; and No. 22, a deeper and more powerful green, with a larger amount of blue.187. PRUSSIAN GREEN,like the preceding, is composed of Prussian blue and gamboge; but contains a very great excess of the former, and is therefore a bluish-green of the utmost depth and transparency, verging on black in its deep washes. Yellow ochre may be employed instead of gamboge, but is not so eligible.A true Prussian green, which has been recommended as a pigment, can be produced as a simple original colour, with a base wholly of iron. It is got by partially decomposing the yellow oxalate of protoxide of iron with red prussiate of potash. We have made this green and given it a fair trial, but our verdict is decidedly againstit. In colour it is far from being equal to a good compound of Prussian blue and gamboge, and it assumes a dirty buff-yellow on exposure to light and air, the film of blue on the oxalate more or less disappearing.Another Prussian green, with a base of cobalt, is obtained by precipitating the nitrate of that metal with yellow prussiate of potash. According to the mode adopted, and the degree of heat, either a light or dark green results; but this also is inferior in colour, and presents no advantage as to permanence.188. SAP GREEN,Verde Vessie, orIris Green, is a vegetal pigment prepared from the juice of the berries of the buckthorn, the green leaves of the woad, the blue flowers of the iris, &c. It is usually preserved in bladders, and is thence sometimes calledBladder Green. When good, it is of a dark colour and glossy fracture, extremely transparent, and a fine natural yellowish green. This gummy juice, inspissated and formed into a cake, is occasionally employed in flower painting. It is, however, a very imperfect pigment, disposed to attract the moisture of the atmosphere, and to mildew; while, having little durability in water and less in oil, it is not eligible in the one and is totally useless in the other.Similar pigments, obtained from coffee-berries,and named Venetian and Emerald Greens, are of a colder colour, equally defective and fugitive, and now obsolete.189. TERRE VERTE,orGreen Earth, is a sober bluish green with a grey cast. It is a species of ochre, containing silica, oxide of iron, magnesia, potash, and water. Not bright and of little power, it is a very durable pigment, being unaffected by strong light or impure air, and combining with other colours without injury. It has not much body, is semi-transparent, and dries well in oil. Veins of brownish or reddish ochre are often found mixed with terre verte, to the detriment of its colour; and there are varieties of this pigment with copper for their colouring matter, which, although generally brighter, are inferior in other respects, and not true terre vertes. Verona Green and Verdetto or Holy Green, are ferruginous native pigments of a warmer hue. These are met with in the Mendip Hills, France, Italy, and the island of Cyprus, and have been used as pigments from the earliest times. Rubens has availed himself much of terre verte, not in his landscapes merely, but likewise in the carnation tints in his figures of a dead Christ. It is evident that much of the glazing is done with this colour: it is, in fact, most useful in glazing; because, having only a thin substance,it can be rendered pale by a small portion of white; although in the end it becomes darker by a concentration of its molecules. Mérimée states that in the greater part of Alexander Veronese's works—in his Death of Cleopatra, in the Louvre, for instance—there are some demi-tints which are too green, and which it is certain were not so originally. Terre verte, therefore, must be employed with caution; and it would be well to ascertain beforehand whether a mineral colour will in time become darker than when first laid on the picture, by putting a drop of oil on the powder in its natural state. If the tone this gives to it be more intense than that which it acquires by being ground up, it may fairly be assumed that it will attain to the same degree of strength whenever, having completely dried, its molecules shall have re-united as closely as it is possible. Umber and terra di Sienna are of this class.In combination with Indian red and Naples yellow, terre verte forms a series of mild russet greens, of much use in middle distance.190.Chrome Arseniateis an agreeable apple-green colour, prepared from arseniate of potash and salts of chromic oxide. It is durable, but possesses no advantages over the chrome oxides, and is of course poisonous.191.Cobalt Green,Rinman's Green, Vert de Zinc or Zinc Green. True cobalt green is made by igniting a very large quantity of carbonate of zinc with a very small quantity of carbonate of cobalt. To give a green tint to an enormous proportion of the former, an inappreciable amount of the latter will suffice. Some samples which were analysed, consisted almost entirely of zinc, there being only two or three per cent. of cobalt present. This green presents an example of a pigment being chemically good and artistically bad, or at least indifferent. It is a moderately bright green, apt to vary in hue according to the mode of manufacture, permanent both alone and compounded, but so sadly deficient in body and power, as to have become almost obsolete. With other physical defects, and a colour inferior to the chrome oxides, cobalt green has never been a favourite with artists, though justly eulogised by chemists.192.Copper Borateis obtained by precipitating sulphate of copper with borax, washing the residue with cold water, and, after drying, igniting it, fusion being carefully avoided. In this manner, a pretty yellowish green is produced, which upon longer ignition assumes a dark green shade: the massis levigated for use. The compound has the objection of being glassy, and possessing little body, but is preferable to verdigris as to permanence.193.Copper Chromemay be prepared by several methods, but the colour is in no case so fine as Scheele's or Schweinfurt green, nor is it as stable.194.Copper Stannate,or Tin-Copper Green, equals in colour any of the copper greens free from arsenic. The cheapest way of making it is to heat 59 parts of tin in a Hessian crucible with 100100 parts nitrate of soda, and dissolve the mass when cold in a caustic alkali. To the clear solution, diluted with water, a cold solution of sulphate of copper is added: a reddish-yellow precipitate falls, which on being washed and dried, becomes a beautiful green. On the palette it would be superfluous, but for common purposes might be found of service.195.Elsner's Greenis also a combination of tin and copper. It is made by adding to a solution of sulphate of copper a decoction of fustic, previously clarified by a solution of gelatine. To this mixture areadded ten or eleven per cent. of protochloride of tin, and lastly an excess of caustic potash or soda. The precipitate is then washed and dried, whereupon it takes a green colour tinged with blue, but without the brightness or durability of the preceding stannate.196.Green Bice,or Green Verditer, is the same in substance as blue verditer, which is converted into green verditer by boiling. This pigment is one of the least eligible of copper greens.197.Green Ochre.By partially decomposing yellow ochre with prussiate of potash, we have produced a fine dark blue-green, resembling Prussian green, of great depth and transparency. There are, however, difficulties in the process; and the results do not warrant us in pronouncing this green superior or equal to a mixture of the ochre and Prussian blue.198.Green Ultramarine

Cobalt, as furnishing a blue colour, is usually associated with alumina, silica, or tin; and, as furnishing a green colour, with zinc. But there is obtainable a compound of zinc and cobalt which gives a blue not only free from green, but inclining rather to red. It is made by adding to a solution of ordinary phosphate of soda in excess a solution first of sulphate of zinc and then of sulphate of cobalt, and washing and igniting the precipitate. The result is a vitreous blue with a purple cast, of little body, and exceedingly difficult to grind. Altogether, it is not unlike smalt, over which it has no advantages as an artistic pigment either in colour or permanence. For tinting porcelain, however, it is admirably adapted, imparting thereto a very pure darkblue of extraordinary beauty. This blue is distinguished from smalt by dissolving in acetic acid.

Compared with the wide range of yellows, or even with reds, the artist finds the number of his blues limited. The perfect native and excellent artificial ultramarines, the good blues of cobalt, the fair Prussian blue, and the doubtful indigo, are the four varieties he has for years been in the habit of using, and is still mainly dependent on. Our division, therefore, into permanent, semi-stable, and fugitive, is easily effected.

In the front rank, pre-eminent among blues as among pigments generally, stands genuine ultramarine. Behind it, are the artificial ultramarines; and behind them again, cobalt and cerulian blue. To a greater or less extent, all these are durable.

Among the semi-stable, must be classed cyanine or Leitch's blue, smalt, and Prussian blue.

To the fugitive, belong indigo and the somewhat more permanent intense blue, Antwerp blue, and the copper blues.

In this list of blues, which grace or disgrace the palette of the present day, there is one colour which, although not permanent, is almost indispensable. As yet, the chemist cannot in all cases lay down the law as to what pigments may or may not be employed. The painter who unnecessarily uses fugitive colours must have little love for his craft, and a poor opinion of the value of his work; but, even with the best intentions and the utmost self-esteem, the artist cannot always confine himself to strictly stable pigments. He has no right to use orpiment instead of cadmium yellow, or red lead instead of vermilion, or copper blue instead of cobalt: he has no business to employ indigo when Prussian blue saddened by black will answer his purpose; but—what pigment can he substitute for Prussian blue itself? None. In its wondrous depth, richness, and transparency, it stands alone: there is no yellow to compare with it, no red to equal it, no blue to rival it. In force and power it is a colour among colours, and transparent beyond them all. The great importance of transparent pigments is to unite with solid or opaque colours of their own hues, giving tone and atmosphere generally, together with beauty and life; to convert primary into secondary, and secondary into tertiary colours, with brilliancy; to deepen and enrich dark colours and shadows, and to impart force and tone to black itself. For such effects, no pigment can vie with Prussian blue. What purples it produces, what greens it gives, what a matchless range of grays; what velvety glow it confers, how it softens the harshness of colours, and how it subdues their glare. No; until the advent of a perfect palette, the artist can scarcelypart with his Prussian blue; nor can the chemist, who has nothing better to offer, hold him to blame. It is for Art to copy Nature with the best materials she possesses: it is for Science to learn the secrets of Nature, and turn them to the benefit of Art.

Orangeis the first of the secondary colours in relation to light, being in all the variety of its hues composed ofyellowandred. A true or perfect orange is such a compound of red and yellow as will neutralize a perfect blue in equal quantity either of surface or intensity; and the proportions of such compound are five of perfect red to three of perfect yellow. When orange inclines to red, it takes the names ofscarlet,poppy, &c.: in gold colour, &c., it leans towards yellow. Combined with green it forms the tertiarycitrine, and with purple the tertiaryrusset: it also furnishes a series of warm semi-neutral colours with black, and harmonizes in contact and variety of tints with white.

Orange is an advancing colour in painting:—in nature it is effective at a great distance, acting powerfully on the eye, diminishing its sensibility in accordance with the strength of the light in which it is viewed. It is of the hue, and partakes of the vividness of sunshine, as it likewise does of all the powers of its components, red and yellow. Pre-eminently awarmcolour, being the equal contrast of or antagonist to blue, to which the attribute ofcoolnesspeculiarly belongs, it is discordant when standing alone with yellow or with red, unresolved by their proper contrasts or harmonizing colours, purple and green. As an archeus or ruling colour, orange is one of the most agreeable keys in toning a picture, from the richness and warmth of its effects. If it predominate therein, for the colouring to be true, the violet and purple should be more or less red, the red more or less scarlet, the yellow more or less intense and orange, and the orange itself be intense and vivid. Further, the greens must lose some of their blue and consequently become yellower, the light blues be more or less light grey, and the deep indigo more or less marrone.

Although the secondary colours are capable of being obtained by admixture of the primaries in an infinitude of hues, tints, and shades; yet simple original pigments of whatever class—whether secondary, tertiary, or semi-neutral—are, it has been said before, often superior to those compounded, both in a chemical and artistic sense. Hence a thoroughly good original orange is only of less value and importance than a thoroughly good original yellow, a greenthan a blue, or a purple than a red. To produce pure and permanent compound hues requires practice and knowledge, and we too often see in the works of painters combinations neither pleasing nor stable. Colours are associated with each other which do not mix kindly, and compounds formed of which one or both constituents are fugitive. As a consequence, mixed tints are frequently wanting in clearness, and, where they do not disappear altogether, resolve themselves into some primary colour; orange becoming red by a fading of the yellow, green yellow by a fading of the blue, and purple blue by a fading of the red. Again, with regard to compound tints, there is the danger of one colourreactingupon and injuring another, as in the case of greens obtained from chrome yellow and Prussian blue, where the former ultimately destroys the latter. Of course a mixture of two permanent pigments which do not react on each other will remain permanent; the green, for instance, furnished by aureolin and native ultramarine lasting as long as the ground itself. To produce, however, the effects desired, the artist does not always stop to consider the fitness and stability of his colours in compounding, even if he possess the needed acquaintance with their physical and chemical properties. At all times, therefore, but especially when such knowledge is slight, good orange, &c., pigments are of moreor less value, as by their use the employment of inferior mixtures is to a great extent avoided. In mingling primary with primary, if one colour does not compound well with the other, or is fugacious, the result is failure; but a secondary is not so easily affected by admixture: a green, for example, is seldom quite ruined by the injudicious addition of blue or yellow; and even if either of the latter be fugitive, the green will remain a green if originally durable. Thus the secondaries, if they are not already of the colour required, may be brightened or subdued, deepened or paled, with comparative impunity. The artist who, from long years of experience, knows exactly the properties and capabilities of the colours he employs, may in a measure dispense with secondary pigments, and obtain from the primaries mixed tints at once stable, beautiful, and pure; but even he must sometimes resort to them, as when a green like emerald or viridian is required, which no mixture of blue and yellow will afford. The primaries, by reason of their not being able to be composed of other colours, occupy the first place on the palette, and are of the first importance; but the secondaries are far too useful to be disregarded, and have a value of their own, which both veteran and tyro have cause to acknowledge.

The list of original orange pigments was once so deficient, that in some old treatises on thesubject of colours, they are not even mentioned. This may have arisen, not merely from their paucity, but from the unsettled signification of the term orange, as well as from improperly calling these pigments reds, yellows, &c. In these days, however, orange pigments are sufficiently numerous to merit a chapter to themselves; they indeed comprise some of the best colours on the palette.

orBurnt Terra di Sienna, is calcined raw Sienna, of a rich transparent brown-orange or orange-russet colour, richer, deeper, and more transparent than the raw earth. It also works and dries better, has in other respects the qualities of its parent colour, and is a most permanent and serviceable pigment in painting generally. For the warm tints in rocks, mud banks, and buildings, this colour is excellent. When mixed with blue it makes a good green; furnishing a bright green with cobalt, and one much more intense with Prussian blue. For the foresea, whether calm or broken by waves, it may be employed with a little madder; while compounded with a small portion of the latter and lamp black, it meets the hues of old posts, boats, and a variety of near objects, as the tints may be varied by modifying the proportions of the component colours. Used with white, it yields a range ofsunny tones; and with aureolin or French blue and aureolin will be found of service, the last compound giving a fine olive green. Similar but fugitive greens are afforded by admixture of burnt Sienna with indigo and yellow or Roman ochre, or raw Sienna; tints which may be saddened into olive neutrals by the addition of sepia, and rendered more durable by substituting for indigo Prussian blue and black. Mixed with viridian, it furnishes autumnal hues of the utmost richness, beauty, and permanence; and, alone, is valuable as a glaze over foliage and herbage. For the dark markings and divisions of stones a compound of Payne's gray and burnt Sienna will prove serviceable; while for red sails the Sienna, either by itself, with brown madder, or with Indian red, cannot be surpassed. For foregrounds, banks and roads, cattle and animals in general, burnt Sienna is equally eligible, both alone and compounded. It has a slight tendency to darken by time.

was first introduced to the art-world at the InternationalExhibitionof 18621862, where it was universally admired for its extreme brilliancy and beauty, a brilliancy equalled by few of the colours with which it was associated, and a beauty devoid of coarseness. We remember well the power it possessed of attracting the eye from a distance;and how, on near approach, it threw nearly all other pigments into the shade. It has in truth a lustrous luminosity not often to be met with, added to a total absence of rankness or harshness. A simple original colour, containing no base but cadmium, it is of perfect permanence, being uninjured by exposure to light, air or damp, by sulphuretted hydrogen, or by admixture. Having in common with cadmium sulphides a certain amount of transparency, it is invaluable for gorgeous sunsets and the like, either alone or compounded with aureolin. Of great depth and power in its full touches, the pale washes are marked by that clearness and delicacy which are so essential in painting skies. As day declines, and blue melts into green, green into orange, and orange into purple, the proper use of this pigment will produce effects both glowing and transparent. Transparency signifies the quality of being seen through or into; and in no better way can it be arrived at than by giving a number of thin washes of determined character, each lighter than the preceding one. With due care in preserving their forms, from the commencement to the termination, such washes of orange will furnish hues the softest and most aerial. For bits of bright drapery, a glaze over autumn leaves, and mural decoration, this colour is adapted; while in illumination it supplies a want formerly much felt. "Withthe exception of scarlet or bright orange," said Mr. Bradley, nine or ten years since, in his Manual of Illumination, "our colours are everything we could wish." As an original pigment, a permanent scarlet does not yet exist; but the brilliancy of cadmium orange cannot be disputed, nor its claim to be the only unexceptionable bright orange known. It even assists the formation of the other colour: remarks the author mentioned, "Brilliancy is obtained by gradation. Suppose a scarlet over-curling leaf, for example. The whole should be painted in pure orange, with the gentlest possible after-touch of vermilion towards the corner under the curl. When dry, a firm line—not wash—of carmine, (of madder, preferable.—Ed.), passed within the outline on the shade side only of the leaf, will give to the whole the look of a bright scarlet surface, but with an indescribable superadded charm, that no merely flat colour can possess." In the same branch of art, illumination, cadmium orange, opposed to viridian, presents a most dazzling contrast, especially if relieved by purple.

belongs to the coal-tar colours, and ought strictly to have been classed therewith. We have preferred, however, to keep it separate, because, as Chinese Orange, it was introduced as a pigment,and has not been employed as a dye. In colour, it somewhat resembles burnt Sienna, enriched, reddened, brightened, and made more transparent, by admixture with crimson lake. From its behaviour, it would seem to be composed of yellow and red, such a compound as magenta and aniline yellow would afford. Its pale washes are uncertain, being apt to resolve themselves into red and yellow, of which the latter appears the most permanent; for, on exposure to light and air, the red more or less flies, leaving here a yellow, and there a reddish-yellow ground: in places both red and yellow disappear. Like all fugitive colours, it is comparatively stable when used in body; but even then it entirely loses its depth and richness, and in a great measure its redness, becoming faded and yellowish. In thin washes or glazing it is totally inadmissible; and, being neither a red, an orange, nor a brown, is unsuited to pure effects. Nevertheless, where it need not be unduly exposed; in portfolio illuminations, for instance, the richness, subdued brilliancy, and transparency of this pigment, justify its adoption. It is not affected by an impure atmosphere.

Aniline colours may be adapted for oil painting by dissolving them in the strongest alcohol, saturating the solution with Dammar resin, filtering the tincture, and pouring the filtrate either on pure water or solution of common salt, stirring well allthe time. The water or brine solution must be at least twenty times the bulk of the tincture. The colour after being collected on a filter, washed, and dried, can be ground with linseed oil, poppy oil, or oil varnishes.

Orange Chrome, orOrange Chromate of Lead, is a sub-chromate of lead of an orange-yellow colour, produced by the action of an alkali on chrome yellow. Like all the chromates of lead, it is characterized by power and brilliancy; but also by a rankness of tone, a want of permanence, and a tendency to injure organic pigments. By reason of its lead base it is subject to alteration by impure air, but is on the whole preferable to the chrome yellows, being liable in a somewhat less degree to their changes and affinities. As, however, a colour has no business to be used if a better can be procured, the recent introduction of cadmium orange renders all risk unnecessary.

Orange de Mars, is a subdued orange of the burnt Sienna class, but without the brown tinge that distinguishes the latter. Marked by a special clearness and purity of tone, with much transparency, it affords bright sunny tints in its pale washes, and combines effectively with white.Being an artificial iron ochre it is more chemically active than native ochres, and needs to be cautiously employed with pigments affected by iron, such as the lakes of cochineal and intense blue.

Orange being a compound colour, the place of original orange pigments can be supplied by mixtures of yellow and red; either by glazing one over the other, by stippling, or by other modes of breaking and intermixing them, according to the nature of the work and the effect required. For reasons lately given, mixed pigments are apt to be inferior to the simple or homogeneous both in colour, working, and other properties; yet some pigments mix and combine more cordially and with better results than others; as is the case with liquid rubiate and gamboge. Generally speaking, the compounding of colours is easier in oil than in water; but in both vehicles trouble will be saved by beginning with the predominating colour, and adding the other or others to it.

Perhaps in this, our first chapter on the secondary colours, and consequently on colours that can be compounded, a few remarks on mixed tints from a chemical point of view will not be deemed superfluous.

There are two ways, we take it, of looking ata picture—from a purely chemical, and from a purely artistic, point of view. Regarded in the first light, it matters little whether a painting be a work of genius or a daub, provided the pigments employed on it are good and properly compounded. The effects produced are lost sight of in a consideration of the materials, their permanence, fugacity, and conduct towards each other. Painting is essentially a chemical operation: with his pigments for reagents, the artist unwittingly performs reaction after reaction, not with the immediate results indeed of the chemist in his laboratory, but often as surely. As colour is added to colour, and mixture to mixture, acid meets alkali, metal animal, mineral vegetable, inorganic organic. With so close a union of opposite and opposing elements, the wonder is not so much that pictures sometimes perish, but that they ever live. It behoves the artist, then, not only to procure the best and most permanent pigments possible, but to compound them in such a manner that his mixed tints may be durable as well as beautiful. To effect or aid in effecting this, although he may not always be able to act upon them, the following axioms should be borne in mind:—

To give illustrations—

Except in the second instance, where the blue is either partially or wholly destroyed—in time, be it remembered, not at once—according to the quantity and strength of the acid in the white, the ultramarine remains unchanged. Hence at first sight our third and fourth conclusions mayappear wrong; inasmuch as, it may be argued, a blue mixture cannot be semi-stable or fugitive when blue is left. To this we reply, unless both constituents are fugitive, a mixture will always more or less possess colour; but, if even one constituent be semi-stable or fugitive, a mixture will slowly but surely losethecolour for which it was compounded, and beas a mixturesemi-stable or fugitive.

It need hardly be observed that the number of permanent orange, green, and purple hues which the artist can compound, depends mainly on the number of permanent yellows, reds, and blues at his disposal. In mixed orange, therefore, a selection of durable yellows and reds is of the first importance. It should, however, be remarked that mixed orange, more sober and less decided, is obtainable by the use of citrine and russet; in the former of which yellow predominates, and in the latter, red: consequently orange results when yellow is added to russet, red to citrine, or citrine to russet.

None of these pigments react on each other, and from them can be produced the most durable mixed orange that yellow and red will afford.

orPenley's Neutral Orange, is a permanent compound pigment composed of yellow ochre and the russet-marrone known as brown madder: it is chiefly valuable in water-colour. Paper, being white, is too opaque to paint upon, without some wash of colour being first passed over it; otherwise the light tones of the sky are apt to look crude and harsh. It must, therefore, be gone over with some desirable tint, that shall break, in a slight degree, the extreme brilliancy of the mere paper. For this purpose, a thin wash of the orange is to be put over the whole surface of the paper with a large flat brush, care being taken never to drive the colour too bare,i.e.never to empty the brush too closely, but always to replenish before more is actually required. This first wash of colour not only gives a tone to the paper, but secures the pencil sketch from being rubbed out.

The reason why, in this compound, yellow ochre, as a yellow, is preferred to any of the others, is, that it is a broken yellow, that is, a yellow slightly altered by having another hue, such as red, or brown, in its composition. It is somewhat opaque too, and hence, from thisquality, is especially adapted for distances. Brown madder also is a subdued red, which, when in combination with the former, produces a neutral orange, partaking of the character of soft light. As a general rule, yellow ochre is to predominate in broad daylight, and brown madder in that which is more sombre and imperfect: hence the pigment can be yellowed or reddened, by the addition of one or the other. For a clear sunset, the neutral orange must be repeated, with a preponderance of ochre at the top, assisted by a little cadmium yellow near the sun; the madder being added downwards.

In treating of distant mountains, a distinction is to be made between them and the clouds, the former requiring solidity, while the latter are only to be regarded as vapour and air. Mountains, being opaque bodies, are acted upon by atmosphere more or less, according to their position, their distance, and the state of the weather. To express this distinction, recourse must be had to an under tint, except where the tone is decidedly blue—an uncommon case. No mixture can give this with such truth as the neutral orange. A wash, therefore, should be passed over the mountains, with nearly all yellow in the high lights, or in the gleams of sunshine, and, on the contrary, almost all brown madder for the shadows. These two degrees of tone must be run into each otherwhile the drawing is wet. A beautiful and soft under tone will thus be given to receive the greys.

called alsoSpanish Ochre, is a very bright yellow or Roman ochre burnt, by which operation it acquires warmth, colour, transparency, and depth. Moderately bright, it forms good flesh tints with white, dries and works well both in water and oil, and is a very good and eligible pigment. It may be used in enamel painting, and has all the properties of its original ochre in other respects.

A redder hue is imparted by mixing the ochre with powdered nitre before ignition, the orange red being subsequently washed with hot water.

Annotto, Annatto, Arnotto, Arnotta, Terra Orellana, Rocou, &c., is met with in commerce under the names of cake anotta, and flag or roll anotta. The former, which comes almost exclusively from Cayenne, should be of a bright yellow colour: the latter, which is imported from the Brazils, is brown outside and red within. It is prepared from the pods of thebixa orellana, and appears generally to contain two colouring matters, a yellow and a red, which are apt to adhere to each other and produce orange. Anottadissolves with difficulty in water, but readily in alcohol and alkaline solutions, from which last it may be thrown down as a lake by means of alum. Being, however, exceedingly fugitive and changeable, it is not fit for painting; but is chiefly employed in dyeing silk, and colouring varnishes and cheese. Very red cheese should be looked upon with suspicion, for although the admixture of anotta is in no way detrimental to health provided the drug be pure, it is commonly adulterated with red lead and ochre. Several instances are on record that Gloucester and other cheeses have been found contaminated with red lead, through having been coloured with anotta containing it, and that this contamination has produced serious consequences.

Bixineis a purified extract of anotta made in France, and used by dyers.

Golden Sulphur of Antimony, or Golden Yellow, is a hydro-sulphuret of antimony of an orange colour, which is destroyed by the action of strong light. It is a bad dryer in oil, injurious to many pigments, and in no respect eligible either in water or oil.

has been improperly classed as a red with vermilion, for though it is of a bright ochrous redin powder, when ground it becomes a bright ochre-orange, and affords with white very pure orange tints. Nevertheless it is a bad pigment, since light soon changes it to a deep russet colour, and foul air reduces it to extreme blackness.

or Monicon, is an iron ochre, being a compound of raw Sienna and Roman ochre burnt, and having all their qualities. It is rather more russet in hue than the pigment known as orange or burnt Roman ochre, has considerable transparency, is rich and durable in colour, and furnishes good flesh tints. As in orange ochre, powdered nitre may be employed in its preparation. Notwithstanding its merits, it is obsolete or nearly so; doubtless because burnt Sienna mixed with burnt Roman ochre sufficiently answers the purpose.

On adding acetate of lead to a potash solution of gamboge, a rich bright orange is precipitated, which may be washed on a filter till the washings are colourless, and preserves its hue with careful drying. The orange which we thus obtained stood well in a book, but it cannot be recommended as an artistic pigment. Perhaps in dyeing, the lead and gamboge solutions might be worth a trial.

is a French pigment, a species of chromic orange, similar to the orange chromate of lead. This name is likewise given to orange oxide of iron.

or Orange Lake. It has been said that the yellows so-called produced from madder are not remarkable for stability, differing therein from the reds, purples, russets, and browns. Like them, this 'orange' is of doubtful colour and permanence, and not to be met with, brilliant and pure, on the palette of to-day. The russet known as Rubens' madder has a tendency to orange.

of a dull orange colour, is an orange protoxide of lead or massicot. Like litharge, it may be employed in the preparation of drying oils, and, being a better drier than white lead, may be substituted for it in mixing with pigments which need a siccative, as the bituminous earths.

Minium sometimes leans to orange; and there is made from ceruse a peculiar red,Mineral Orange.

or Realgar, has also been called Red Orpiment,improperly, since it is a brilliant orange, inclining to yellow. There are two kinds, a native and an artificial, of which the former is thesandaracof the ancients, and is rather redder than the latter. They possess the same qualities as pigments, and as such resemble yellow orpiment, to which the old painters gave the orange hue by heat, naming it alchemy and burnt orpiment. Orange orpiment contains more arsenic and less sulphur than the yellow, and is of course highly poisonous. It is often sophisticated with brickdust and yellow ochre.

is produced when bichromate of potash is added to a neutral salt of the protoxide of thallium, as an orange-yellow precipitate. The scarcity of the metal precludes their present introduction as pigments, but if the chromates of thallium were found to resist the action of light and air, and not to become green by deoxidation of the chromic acid, they might possibly prove fitted for the palette. It is a question whether theirveryslight solubility in water would be a fatal objection; and, although they would be liable to suffer from a foul atmosphere, we are inclined to think the effects would not be so lasting as in the chromates of lead. Like lead sulphide, the sulphide of thallium ranges from brown to brownish-black, or grey-black; and, like it too,is subject to oxidation and consequent conversion into colourless sulphate. It is, however, much more readily oxidized than sulphate of lead; and hence the thallium chromates would doubtless soon regain their former hue on exposure to a strong light.

Mr. Crookes, who discovered this new metal in 1861, believes that the deep orange shade observable in some specimens of sulphide of cadmium is due to the presence of thallium. He has frequently found it, he says, in the dark-coloured varieties, and considers the variations of colour in cadmium sulphide to be owing to traces of thallium. That thallium affects the colour is most probable, but it is not necessarily the cause of the orange hue. The tint of cadmium sulphide is a mere matter of manufacture, seeing that from the same sample of metal there can be obtained lemon-yellow, pale yellow, deep yellow, orange-yellow, and orange-red. With deference to the opinion of a chemist so distinguished, we hold that thallium rather impairs the beauty of cadmium sulphide than imparts to it an orange shade, the thallium being likewise in the form of sulphide, and therefore more or less black. On chromate of cadmium, made with bichromate of potash, thallium would naturally confer an orange hue.

is obtainable by wet and dry methods as ayellowish-red, or, when reduced to powder, an orange-yellow, uranate of baryta. It is an expensive preparation, superfluous as a pigment.

When hydrochloric acid and zinc are made to act on nitro-prusside of sodium, a corresponding zinc compound is formed of a deep orange colour, slightly soluble in water, and not permanent.

For a secondary colour, orange is well represented on the modern palette, and can point to some pigments as good and durable as any to be found among the primaries. Burnt Sienna, cadmium orange, Mars orange, neutral orange, and orange or burnt Roman ochre, are all strictly permanent. The so-called orange vermilions were, it will be remembered, classed among the reds.

As semi-stable, must be ranked chrome orange; and as fugitive, Chinese orange, orange orpiment, and orange lead.

From the foregoing division, the predominance of eligible orange pigments over those less trustworthy is manifest. Unfortunately, with many painters it is not so manifest that their secondary and compound colours should receive as much attention as the primaries, and that it is their duty, not only to the art which they practice, but to the patrons for whom they practiceit, that their orange and green and purple hues, should be as durable as their yellows, reds, and blues. For such, the introduction of a new permanent pigment is of little interest, unless its colour be primary; so wedded are they to that passion for compounding which the chemist views with dismay. With dismay, because he knows that the rules of mixture are severe, and cannot with impunity be altered; that, although disguised in oil or gum, each pigment is a chemical compound, with more or less of affinity and power, more or less likely to act or be acted upon. Because he knows that, except with the most experienced artists, compounding leads to confusion; and that in it the temptations to use semi-stable or fugitive colours are strong. Look at those tables of mixed tints of which artist-authors are so fond, and tell us whether they always bear scrutiny—surely not. Admirable, perfect as these tints may be in an artistic sense, how often is their beauty like the hectic flush of consumption, which carries with it the seeds of a certain death. Will that orange where Indian yellow figures ever see old age, or that green with indigo, or purple with cochineal lake? Will they not rather spread over the picture the Upas-tree of fugacity, and kill it as they die themselves!

Green, which occupies the middle station in the natural scale of colours and in relation to light and shade, is the second of the secondary colours. It is composed of the extreme primaries,yellowandblue, and is most perfect in hue when constituted in the proportions of three of yellow to eight of blue of equal intensities; because such a green will exactly neutralize and contrast a perfect red in the ratio of eleven to five, either of space or power. Of all compound colours, green is the most effective, distinct, and striking, causing surprise and delight when first produced by a mixture of blue and yellow, so dissimilar to its constituents does it appear to the untutored eye. Compounded with orange, green converts it into the one extreme tertiarycitrine; while mixed with purple, it becomes the other extreme tertiaryolive: hence its relations and accordances are more general, and its contrasts more agreeable with all colours, than those of any other individualcolour. Accordingly it has been adopted very wisely in nature as the common garb of the vegetal creation. It is, indeed, in every respect a central or medial colour, being the contrast, compensatory in the proportion of eleven to five, of the middle primaryred, on the one hand, and of the middle tertiaryrusset, on the other; while, unlike the other secondaries, all its hues, whether tending to blue or yellow, are of the same denomination.

These attributes of green, which render it so universally effective in contrasting colours, cause it also to become the least useful in compounding them, and the most apt to defile other colours in mixture. Nevertheless it forms valuable semi-neutrals of the olive class withblack, for of such subdued tones are those greens by which the more vivid tints of nature are opposed. Accordingly, the various greens of foliage are always more or less semi-neutral in hue. As green is the most general colour of vegetal nature and principal in foliage; so red, its harmonizing colour, with compounds of red, is most general and principal in flowers. Purple flowers are commonly contrasted with centres or variegations of bright yellow, as blue flowers are with like relievings of orange; and there is a prevailing hue, or character, in the green colour of the foliage of almost every plant, by which it is harmonized with the colours of its flowers.

The chief discord of green is blue; and when they approximate or accompany each other, they require to be resolved by the opposition of warm colours. It is in this way that the warmth of distance and the horizon reconciles the azure of the sky with the greenness of a landscape. Its less powerful discord is yellow, which needs to be similarly resolved by a purple-red, or its principles. In tone, green is cool or warm, sedate or gay, either as it inclines to blue or to yellow; yet in its general effects it is cool, calm, temperate, and refreshing. Having little power in reflecting light, it is a retiring colour, and readily subdued by distance: for the same reason, it excites the retina less than most colours, and is cool and grateful to the eye. As a colour individually, green is eminently beautiful and agreeable, but it is more particularly so when contrasted by its compensating colour, red, as it often is in nature, even in the green leaves and young shoots of plants and trees. "The autumn only is called the painter's season," remarks Constable, "from the great richness of the colours of the dead and decaying foliage, and the peculiar tone and beauty of the skies; but the spring has, perhaps, more than an equal claim to his notice and admiration, and from causes not wholly dissimilar,—the great variety of tints and colours of the living foliage, accompanied by their flowers and blossoms. Thebeautiful and tender hues of the young leaves and buds are rendered more lovely by being contrasted, as they now are, with the sober russet browns of the stems from which they shoot, and which still show the drear remains of the season that is past."

The number of pigments of any colour is in general proportioned to its importance; hence the variety of greens is very great, though the classes of those in common use are not very numerous. Of the three secondaries, green is the colour most often met with, and, consequently, the most often compounded: for this last reason, perhaps, the palette is somewhat deficient in really good original greens—more deficient than there is any necessity for.

By numerous methods both wet and dry, oxides of chromium are obtainable pale and deep, bright and subdued, warm and cool, opaque and transparent: sometimes hydrated, in which case they cannot be employed in enamelling; and sometimes anhydrous, when they are admissible therein. But whatever their properties may be, chemical, physical, or artistic, they are all strictly stable. Neither giving nor receiving injury by admixture, equally unaffected by foul gas and exposure to light, air, or damp, these oxides are perfectly unexceptionable in every respect.For the most part they are eligible in water and oil, drying well in the latter vehicle, and requiring in the former much gum. They have long been known as affording pure, natural, and durable tints; but, until within the last few years, have been rather fine than brilliant greens. Lately, however, processes have been devised, yielding them almost as bright, rich, and transparent, as the carmine of cochineal itself.

Opaque Oxide of Chromium,Green Oxide of Chromium,Chrome Oxide,True Chrome Green,Native Green,&c., is found native in an impure state as Chrome Ochre, but is always artificially prepared for artistic use. Obtained anhydrous by dry modes, this is the only chrome oxide available in enamelling, and is the one seen on superior porcelain. It is a cold, sober sage green, deep-toned, opaque, and, although dull, agreeable to the eye. Its tints with white are peculiarly delicate and pleasing, possessing a silvery luminous quality, and giving the effect of atmosphere. Being very dense and powerful, it must be employed with care to avoid heaviness, and is preferably diluted with a large quantity of white, or compounded with transparent yellow. In the hands of a master, this gray-green furnishes lustrous hues with brown pink, Italian pink, and Indian yellow; three beautiful butfugitive pigments, of which the two last may be replaced by aureolin. Of this Mr. Penley observes, "as adapted for the colouring of foliage and herbage, it is impossible to say too much in its praise. It imparts the vividness and freshness of nature to every colour with which it is combined;" and he brackets oxide of chromium with aureolin as a compound hue "extremely useful." In flat tints, the oxide sometimes does not wash well in water.

being deficient in body, is only eligible in oil. A very pale greyish-white green in powder, it gives an agreeable yellowish green of some depth in oil, moderately bright, but not very pure or clear.

We are acquainted with another transparent chrome oxide of far greater beauty, brightness, purity, and clearness than the above. Of a bluish green hue, a difficulty in getting it to mix with oil renders it at present unavailable.

orFrench Veronese Green, is a comparatively recent introduction, similar in colour and general properties to the following; beside which, however, it appears dull, muddy, and impure. It is often adulterated with arsenic to an enormous extent, which interferes with its transparency,mars its beauty, and renders it of course rankly poisonous.

is a still later addition to the palette, and the only permanent green which can be described as gorgeous, being not unlike the richest velvet. Pure and clear as the emerald, it may be called the Prussian Blue of Greens, of such richness, depth, and transparency is it. In hue of a bluish-green, its deepest shades verge on black, while its light tints are marked by transparent clearness unsurpassed. No compound of blue and yellow will afford a green at once so beautiful and stable, so gifted with the quality of light, and therefore so suited for aerial and liquid effects. Used with aureolin, it gives foliage greens sparkling with sunshine; and, fitly compounded, will be found invaluable for the glassy liquidity of seas, in painting which it becomes incumbent to employ pigments more or less transparent. "The general failing in the representation of the sea is, that instead of appearing liquid and thin, it is made to bear the semblance of opacity and solidity. In order to convey the idea of transparency, some object is often placed floating on the wave, so as to give reflection; and it is strange that we find our greatest men having recourse to this stratagem. To say it is not true in all cases, is saying too much; but this we doassert, that as a general principle it is quite false, and we prove it in this way: water has its motion, more or less, from the power of the wind; it is acted upon in the mass, and thus divided into separate waves, and these individually have their surface ruffled, which renders them incapable of receiving reflection. The exception to this will be, where the heaving of the sea is the result of some gone-by storm, when the wind is hushed, and the surface becomes bright and glassy. In this state, reflections are distinctly seen. Another exception will be in the hollow portion of the waves, as they curl over, and dash upon the shore."

As viridian, like the sea, is naturally "liquid and thin, bright and glassy," the extract we have quoted from Mr. Penley, points to this green as a pigment peculiarly adapted for marine painting; in which, it may be added, its perfect permanence and transparency will be appreciated in glazing. Its fitness for foliage has been remarked; but in draperies the colour will prove equally useful, and in illumination will be found unrivalled. In the last branch of art, indeed, viridian stands alone, not only through its soft rich brilliancy, but by the glowing contrast it presents with other colours: employed as a ground, it throws up the reds, &c., opposed to it, in a marvellous manner. Like the three preceding oxides of chromium, viridian neither injures noris injured by other pigments; is unaffected by light, damp, or impure air; and is admissible in fresco. In enamelling it cannot be used; the colour, depending on the water of hydration, being destroyed by a strong heat.

are commercially known asEmerald Green,Malachite Green,Scheele's Green,Schweinfurt Green,Verdigris,Green Bice,Green Verditer,Brunswick Green,Vienna Green,Hungary Green,Green Lake,Mineral Green,Patent Green,Mountain Green,Marine Green,Saxon Green,French Green,African Green,Persian Green,Swedish Green,Olympian Green,Imperial Green,Mitis Green,Pickle Green, &c.

The general characteristics of these greens are brightness of colour, well suited to the purposes of house-painting, but seldom adapted to the modesty of nature in fine art; considerable permanence, except when exposed to the action of damp and impure air, which ultimately blacken most of them; and good body. They have a tendency to darken by time, dry well as a rule in oil, and are all more or less poisonous, even those not containing arsenic.

Schweinfurt Green,Vienna Green,Imperial Green,Brunswick Green,Mitis Green, &c., is a cupric aceto-arsenite, prepared on the large scale bymixing arsenious acid with acetate of copper and water. It differs from Scheele's Green, or cupric arsenite, in being lighter, more vivid, and more opaque. Powerfully reflective of light, it is perhaps the most durable pigment of its class, not sensibly affected by damp nor by that amount of impure air to which pictures are usually subject: indeed it may be ranked as permanent both in itself and when in tint with white. It works better in water than in oil, in which latter vehicle it dries with difficulty. Bearing the same relation to greens generally as Pure Scarlet bears to reds, its vivid hue is almost beyond the scale of other bright pigments, and immediately attracts the eye to any part of a painting in which it may be employed. Too violent in colour to be of much service, it has the effect, when properly placed, of toning down at once, by force of contrast, all the other greens in a picture. If discreetly used, it is occasionally of value in the drapery of a foreground figure, where a bright green may be demanded; or in a touch on a gaily painted boat or barge. When required, no mixture will serve as a substitute. Compounded with aureolin, it becomes softened and semi-transparent, yielding spring tints of extreme brilliancy and beauty.

orSwedish Green, resembles the preceding varietyin being a compound of copper and arsenic, and therefore rankly poisonous; but differs from it in containing no acetic acid, in possessing less opacity, and in having a darker shade. It is a cupric arsenite, with the common attributes of emerald green, under which name it is sometimes sold. Of similar stability, it must not be employed with the true Naples yellow or antimoniate of lead, by which it is soon destroyed.

Upon the lavish use of this dangerous pigment in colouring toys, dresses, paper-hangings, artificial leaves, and even cheap confectionery, it is not our province to enlarge: the constant-recurring diseases and deaths, which, directly or indirectly, result from the employment of arsenical pigments, are such every-day facts that they are merely deplored and forgotten. With arsenic on our heads, our clothes, our papers, our sweets, ourchildren'splaythings, we are so accustomed to live—and die—in a world of poison, that familiarity with it has bred contempt. Into the fatal popularity, therefore, of arsenical colours for decorative purposes, we shall not further enter; but it behoves us to deprecate their presence, and the presence of all poisonous pigments, in colour-boxes for the young. It is one of the pleasures of childhood to suck anything attractive that comes in its way, openly if allowed, furtively otherwise: and as in early life we have a preference for brilliancy, so vivid a pigment asScheele's green is an object of special attention. Artistically, it matters little whether a pigment is noxious or not, but we hold that poison should not be put into the hands of the young; and indeed are of opinion that a box of colours is about the worst present a child can receive.

orMountain Green, is met with in Cumberland, and is also found in the mountains of Kernhausen, whence it is sometimes calledHungary Green. It is prepared from malachite, a beautiful copper ore employed by jewellers, and is a hydrated dicarbonate of copper, combined with a white earth, and often striated with veins of mountain blue, to which it bears the same relation that green verditer bears to blue verditer. The colour, which may be extracted from the stone by the process followed for native ultramarine, varies from emerald-green to grass-green, and inclines to grey. It has been held in great esteem by some, and considered strictly stable, on the assumption, probably, that a pigment obtained from a stone like ultramarine, and by the same method, could not be otherwise than permanent. That it is so, with respect to light and air, there is no denying; but the green, when separated from the ore and purified for artistic use, is merely a carbonate of copper, and therefore subject to the influence of damp and impure air, in common with other non-arsenical copper colours. As a pigment, native malachite green has the same composition, or very nearly the same, as that which can be artificially produced, and answers to the same tests. Water-rubs of the two varieties which we exposed to an atmosphere of sulphuretted hydrogen became equally blackened by the gas. Practically, there is little or no difference between them: both preserve their colour if kept from damp and foul air, both are injured by those agents, and both are liable to darken in time, especially when secluded from light. The artificial, however, can be obtained of a much finer colour than the natural, which it may be made to resemble by admixture with mineral gray. On the whole, they can scarcely be recommended for the palette, and are certainly inferior in durability to Scheele's and Schweinfurt greens. In fresco painting they have been pronounced admissible; but, apart from the question of damp, we should deem the conjunction of lime with carbonate of copper not favourable to permanence. By the action of alkalies, even the native green malachite may be converted into blue; and it becomes a question whether the dingy greenish-blue on some ancient monuments was not originally malachite green.

orViride Æris, is of two kinds, common or impure, and crystallized orDistilled Verdigris, or, more properly, refined verdigris. The best is made at Montpellier in France, and is a sub-acetate of copper of a bright green colour inclining to blue. The least durable of the copper greens, it soon fades as a water-colour by the action of light, &c., and becomes first white and ultimately black by damp and foul gas. In oil, verdigris is permanent with respect to light and air, but moisture and an impure atmosphere change its colour, and cause it to effloresce or rise to the surface through the oil. It dries rapidly, and is exceptionally useful with other greens or very dark colours. In varnish it stands better; but cannot be considered safe or eligible, either alone or compounded. Vinegar dissolves it, forming a solution used for tinting maps, and formerly much employed for colouring pickles, &c.

The painters, who lived at the time when the arts were restored in Italy, used this pigment; and the bright greens seen in some old pictures are made by glazings of verdigris. It is often largely adulterated with chalk and sulphate of copper.

Green, being a compound of blue and yellow, may be got by combining those colours in the several ways of working—by mixing, glazing, hatching, or otherwise blending them in the proportions of the various hues required. To obtain apuregreen, which consists of blue and yellow only, a blue should be chosen tinged with yellow rather than with red, and a yellow tinged with blue. If either a blue or a yellow were taken, tinged with red, this latter colour would go to produce some grey in the compound, which would tarnish the green. The fine nature-like greens, which have lasted so well in some of the pictures of the Italian schools, appear to have been compounded of ultramarine, or ultramarine ashes and yellow. Whatever pigments are employed on a painting in the warm yellow hues of the foreground, and blue colouring of the distance and sky, are advantageous for forming the greens in landscape, &c., because they harmonize better both in colouring and chemically, and impart homogeneity to the whole: a principle conducive to a fine tone and durability of effect, and applicable to all mixed tints. In compounding colours, it is desirable not only that they should agree chemically, but that they should have, as far as possible, the same degree of durability. In these respects, aureolin and ultramarine, gamboge and Prussian blue, Indian yellow and indigo, are all judicious mixtures, although not all to be recommended.

The foregoing yellows and blues are in no wise inimical to each other, and yield the best mixed greens, chemically considered, the palette can afford. In an artistic sense, we confess, the result is not so satisfactory: the list of blues, it must be admitted, being somewhat scant. Among the latter there is no pigment with the wonderful depth, richness, and transparency of Prussian blue, and none consequently which will furnish with yellow a green of similar quality. That the artist, therefore, will dispense with Prussian blue, it would be too much to expect. There is, however, less necessity for it since the introduction of viridian, a green resembling that which is produced by admixture of Prussian blue and yellow, and which may be varied in hue by being compounded with aureolin or ultramarine. Our object in this work is to give precedence tothe chemical rather than the artistic properties of pigments, to separate the strictly stable from the semi-stable, and the semi-stable from the fugitive. A colour or a mixture may be chemically bad but artistically good, and vice versâ; but the chemist looks upon no pigment or compound with favour unless it be perfectly permanent, and ignores its mere beauty when void of durability. Hence, all artistic considerations are set aside in our lists of permanent pigments: if it be possible to use them alone, so much the better for the permanence of painting; if not, so much the worse will it be, according to the degree of fugacity of the colours employed.

and the three succeeding varieties, are greens resembling each other in being semi-stable, and more or less transparent. Bronze is a species of Prussian green, of a dull blue-black hue. In its deep washes it appears a greenish-black with a coppery cast. It is used in ornamental work, and sometimes as a background tint for flower pieces.

commonly so called, are compounds of chromate of lead and Prussian blue, a mixture which is also known asBrunswick Green. Fine bright greens, they are suited to the ordinary purposesof mechanic painting, but are quite unfit for the artist's craft, chrome yellow reacting upon and ultimately destroying Prussian blue when mixed therewith. For the latter, cheap cobalts and ultramarines are preferably substituted, although they do not yield greens of like power and intensity.

Under the names of English Green, Green Cinnabar, &c., 'new' green pigments have been from time to time introduced, which have turned out mixtures of Prussian blue and chromate of lead; not made, however, by compounding the two, but directly by processes similar to the following:—A mixed solution of the acetates of lead and iron is added to a mixed solution of the yellow prussiate and chromate of potash, the necessary acetate of iron being obtained by precipitating a solution of acetate of lead by sulphate of iron, and filtering the supernatant liquid. Or; to a solution of Prussian blue in oxalic acid, first chromate of potash is added, and then acetate of lead.

By the last process, superior and more permanent chrome greens may be produced, free from lead, by using chloride of barium or nitrate of bismuth in place of the acetate of lead. Chromate of baryta, or chromate of bismuth is then formed, neither of which acts on the Prussian blue.

It should be added that where the latter pigment is present, no green will serve for painting walls containing lime, as its action alters the tint of the Prussian blue.

is a compound of Prussian blue and gamboge, two pigments possessing a like degree of stability, and perfectly innocuous to each other. It is a mixture more durable and more transparent than chrome greens made with chromate of lead. There are two varieties in common use—No. 11, a light grass green, in which the yellow predominates; and No. 22, a deeper and more powerful green, with a larger amount of blue.

like the preceding, is composed of Prussian blue and gamboge; but contains a very great excess of the former, and is therefore a bluish-green of the utmost depth and transparency, verging on black in its deep washes. Yellow ochre may be employed instead of gamboge, but is not so eligible.

A true Prussian green, which has been recommended as a pigment, can be produced as a simple original colour, with a base wholly of iron. It is got by partially decomposing the yellow oxalate of protoxide of iron with red prussiate of potash. We have made this green and given it a fair trial, but our verdict is decidedly againstit. In colour it is far from being equal to a good compound of Prussian blue and gamboge, and it assumes a dirty buff-yellow on exposure to light and air, the film of blue on the oxalate more or less disappearing.

Another Prussian green, with a base of cobalt, is obtained by precipitating the nitrate of that metal with yellow prussiate of potash. According to the mode adopted, and the degree of heat, either a light or dark green results; but this also is inferior in colour, and presents no advantage as to permanence.

Verde Vessie, orIris Green, is a vegetal pigment prepared from the juice of the berries of the buckthorn, the green leaves of the woad, the blue flowers of the iris, &c. It is usually preserved in bladders, and is thence sometimes calledBladder Green. When good, it is of a dark colour and glossy fracture, extremely transparent, and a fine natural yellowish green. This gummy juice, inspissated and formed into a cake, is occasionally employed in flower painting. It is, however, a very imperfect pigment, disposed to attract the moisture of the atmosphere, and to mildew; while, having little durability in water and less in oil, it is not eligible in the one and is totally useless in the other.

Similar pigments, obtained from coffee-berries,and named Venetian and Emerald Greens, are of a colder colour, equally defective and fugitive, and now obsolete.

orGreen Earth, is a sober bluish green with a grey cast. It is a species of ochre, containing silica, oxide of iron, magnesia, potash, and water. Not bright and of little power, it is a very durable pigment, being unaffected by strong light or impure air, and combining with other colours without injury. It has not much body, is semi-transparent, and dries well in oil. Veins of brownish or reddish ochre are often found mixed with terre verte, to the detriment of its colour; and there are varieties of this pigment with copper for their colouring matter, which, although generally brighter, are inferior in other respects, and not true terre vertes. Verona Green and Verdetto or Holy Green, are ferruginous native pigments of a warmer hue. These are met with in the Mendip Hills, France, Italy, and the island of Cyprus, and have been used as pigments from the earliest times. Rubens has availed himself much of terre verte, not in his landscapes merely, but likewise in the carnation tints in his figures of a dead Christ. It is evident that much of the glazing is done with this colour: it is, in fact, most useful in glazing; because, having only a thin substance,it can be rendered pale by a small portion of white; although in the end it becomes darker by a concentration of its molecules. Mérimée states that in the greater part of Alexander Veronese's works—in his Death of Cleopatra, in the Louvre, for instance—there are some demi-tints which are too green, and which it is certain were not so originally. Terre verte, therefore, must be employed with caution; and it would be well to ascertain beforehand whether a mineral colour will in time become darker than when first laid on the picture, by putting a drop of oil on the powder in its natural state. If the tone this gives to it be more intense than that which it acquires by being ground up, it may fairly be assumed that it will attain to the same degree of strength whenever, having completely dried, its molecules shall have re-united as closely as it is possible. Umber and terra di Sienna are of this class.

In combination with Indian red and Naples yellow, terre verte forms a series of mild russet greens, of much use in middle distance.

is an agreeable apple-green colour, prepared from arseniate of potash and salts of chromic oxide. It is durable, but possesses no advantages over the chrome oxides, and is of course poisonous.

Rinman's Green, Vert de Zinc or Zinc Green. True cobalt green is made by igniting a very large quantity of carbonate of zinc with a very small quantity of carbonate of cobalt. To give a green tint to an enormous proportion of the former, an inappreciable amount of the latter will suffice. Some samples which were analysed, consisted almost entirely of zinc, there being only two or three per cent. of cobalt present. This green presents an example of a pigment being chemically good and artistically bad, or at least indifferent. It is a moderately bright green, apt to vary in hue according to the mode of manufacture, permanent both alone and compounded, but so sadly deficient in body and power, as to have become almost obsolete. With other physical defects, and a colour inferior to the chrome oxides, cobalt green has never been a favourite with artists, though justly eulogised by chemists.

is obtained by precipitating sulphate of copper with borax, washing the residue with cold water, and, after drying, igniting it, fusion being carefully avoided. In this manner, a pretty yellowish green is produced, which upon longer ignition assumes a dark green shade: the massis levigated for use. The compound has the objection of being glassy, and possessing little body, but is preferable to verdigris as to permanence.

may be prepared by several methods, but the colour is in no case so fine as Scheele's or Schweinfurt green, nor is it as stable.

or Tin-Copper Green, equals in colour any of the copper greens free from arsenic. The cheapest way of making it is to heat 59 parts of tin in a Hessian crucible with 100100 parts nitrate of soda, and dissolve the mass when cold in a caustic alkali. To the clear solution, diluted with water, a cold solution of sulphate of copper is added: a reddish-yellow precipitate falls, which on being washed and dried, becomes a beautiful green. On the palette it would be superfluous, but for common purposes might be found of service.

is also a combination of tin and copper. It is made by adding to a solution of sulphate of copper a decoction of fustic, previously clarified by a solution of gelatine. To this mixture areadded ten or eleven per cent. of protochloride of tin, and lastly an excess of caustic potash or soda. The precipitate is then washed and dried, whereupon it takes a green colour tinged with blue, but without the brightness or durability of the preceding stannate.

or Green Verditer, is the same in substance as blue verditer, which is converted into green verditer by boiling. This pigment is one of the least eligible of copper greens.

By partially decomposing yellow ochre with prussiate of potash, we have produced a fine dark blue-green, resembling Prussian green, of great depth and transparency. There are, however, difficulties in the process; and the results do not warrant us in pronouncing this green superior or equal to a mixture of the ochre and Prussian blue.

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