CHAPTER VI.ADULTERATIONANDDETECTION.

The Teas of commerce are subject to four principal descriptions of sophistication—“Facing” or Coloring with deleterious compounds, in order to enhance their appearance;—Substituting with spent, partially-used or exhausted leaves to increase their bulk and reduce the cost;—Mixing or blending with spurious or foreign leaves, and—Sanding or adulterating with a variety of mineral matter, chiefly iron or steel filings, to add to the weight. Each trade has its own special form of adulteration, and as in the milk business the most prevalent sophistications are watering and skimming, so in the Tea-trade the besetting malpractice is coloring and mixing with or substitution of partially-exhausted tea leaves, so that the main efforts of experts and tea-analysts should be directed more to this form of adulteration. The other forms have received some attention from chemists and others interested in the article, but not to the extent which the importance of the subject merits. But it is against the two former most common and dangerous forms of adulteration that the principal efforts of tea-analysts and inspectors should more particularly be directed; and, while considerable of this nefarious and positively injurious work is done in the countries of importation, by far the greater portion is perpetrated in the countries of production. For consummate skill in the “tricks of trade,”the Chinese as a people have long been proverbial. “They are a self-ended people,” says an old writer, “having the same reputation in Asia that the Jews have in Europe.” Yet there are strong reasons for stating that many dealers in our own and other tea-drinking countries have become expert imitators of their methods, especially in the minor forms of coloring, mixing, repacking and refacing. The sophistications in our own country being chiefly confined to the admixture of damaged, stained and tainted teas with sound, pure or high-grade goods, with the object of concealing or disguising their defects, and the substitution of one variety for another by repacking and relabeling. The latter form being practiced to a much greater extent than most people imagine, giving rise to a special branch of business in nearly all of the larger cities.

Of the various forms of adulteration practiced in China and Japan artificial coloring or “facing” is perhaps the most prevalent and glaring. The material used for the purpose is usually composed of Prussian blue, gypsum, indigo,turmeric, and more frequently, China clay, a whitish iridescent powder, resembling mica, variously composed, but generally consisting ofkaolin(soapstone), and sulphate of lime. While that in use in Japan is not known, its composition being a secret, known only to the manufacturers, but is evidently a preparation of gypsum and kaolin, the Japanese contending that it is a vegetable compound pure and simple. That kaolin is used in its preparation can hardly be denied, as kaolin contains sulphur, and many of the lower grades of Japan teas are found on infusion to possess a slightly sulphurous odor. It has been proved, however, whatever its nature, to be less harmful andinjurious than the Chinese compound, and used only in the manipulation and sophistication of the lower or commoner grades of tea in that country.

The process of coloring or facing Green teas is performed by placing a portion of Prussian blue in a porcelain bowl, not unlike a chemist’s mortar, and pulverizing it into a fine powder, a small quantity of gypsum being meanwhile burned over a charcoal fire, to soften it, after which it is ground fine. The two substances are next mixed together, in the proportions of one part blue to four parts gypsum, both making in combination a light-blue preparation, in which state it is applied to the leaves during the last process of firing, about five minutes prior to removal from the pans, the time being regulated by a burning joss stick. The Saihoo taking a handful of the compound, scatters it over the leaves while in the pans, other operators tossing and turning the leaves around rapidly with their hands meantime in order that it may equally diffuse among them. One ounce of coloring-matter will face fifteen pounds of leaves, imparting to them a dull leaden-blue hue, and “glossy” or greasy appearance, readily detected in the hand. In many districts, most notably in Ningpo and Canton,turmeric, kaolin, and China clay are more extensively employed for the purpose. This almost transparent form of adulteration is readily detected in the following manner:—

(1) When the tea is heavily coated it may be easily recognized by its dull leaden-blue color and greasy appearance in the hand, or by placing a small quantity of the leaves on a piece of glass or smooth table, on removing them the coloring-matter will be found adhering to the hands, glass or table, and its nature, whether Prussian blue,turmeric, kaolin or indigo, readily determinedwith the aid of a microscope. (2) When only lightly colored or suspected, place a sample of the leaves in a cup or wine-glass and pour on briskly boiling water and stir well for two or three minutes, then strain well through a thin muslin cloth. The coloring-matter, if any, will be found adhering to the cloth, that passing through, sticking to the sides, or forming a sediment at the bottom of the vessel into which it is strained. If these deposits be treated with a preparation of chlorine, or a solution of chloride of lime, and turn white, the coloring substance used is indigo. But if treated with a little potash, and it becomes brown, it will prove to be Prussian blue, the application of a little sulphuric acid having the effect of turning it blue again.

What are known to trade as “Canton Green teas” are made from tea-dust and exhausted leaves ground up fine and aglutinized with a preparation of gum, glue or other starchy substance to unite and hold them together and then artificially colored or glazed. This fabrication is readily detected by crushing the so-called leaves between the fingers or rubbing them between the hands, upon which they leave a yellowish-brown stain, greasy in nature. Or by powdering a small quantity of the alleged leaves and treating the dust with a dilution of sulphuric acid it becomes very much discolored, and if it assumes a leaden-blue color on the application of caustic potash it is colored with Prussian blue. Again, place a small quantity of the leaves in a cup or glass and pour on boiling water, they will immediately begin to disintegrate and form a thick, gluey deposit at the bottom of the vessel. By treating this precipitate with a little iodine the mass will become separated and dissolve into its original dust.

FOREIGN OR SPURIOUS LEAVES IN TEA.

Another reprehensible form of adulteration is the substitution or admixture of foreign or spurious leaves obtained from other plants, which resemble in structure but differ widely in character from the true tea-leaf, such as those of the willow, plum or ash. Millions of pounds of these leaves are annually picked, cured and colored in the same manner as tea in China, and used for the purpose of increasing the bulk and reducing the cost, while in England, particularly, the leaves of the birch, elm, willow, chestnut, poplar and hawthorne have been extensively used for the same purpose. The coloring material used in the latter country differs from that used in China and Japan being still more dangerous and injurious to health. This form of adulteration, however, is trivial when compared with the former one, but, nevertheless, the expert and analyst are frequently called upon to deal with it to a much greater extent than most people imagine.

Such foreign leaves in tea may be best detected by their botanical character or by the absence of the special structural marks which distinguish the genuine tea-leaf from that of all other leaves in the vegetable kingdom, for while the true leaf bears a strong resemblance to that of the willow, ash and plum, it varies, however, in size form and structure. The border of the true tea-leaf is more regularly serrated, the serration stopping just short of the stalk, and the venations are very characteristic, the veins running out from the mid-rib almost parallel to one another, but altering their course before the border of the leaf is reached, and turning so as to leave a bare space just within the border of the leaf. So that in making an examination of a sample of tea for the purpose of ascertaining whether these distinctive characteristics are present in the leaves under treatment, it will be foundconvenient to pour hot water on them so as to soften, uncurl and spread them out more easily, as otherwise considerable difficulty will be experienced owing to the brittleness of the tea-leaves in the dry state.

CHINESE TEA-LEAF.

JAPANESE TEA-LEAF.

The leaf of China Green tea is much broader than that of Black in proportion to its length, but not so thick, and somewhat accuminate or curled at the apex, that of Black being elliptical, oblong and flat in shape, long and pointed, that of Green being much shorter and rounder in form.

INDIA TEA-LEAF.

CEYLON HYBRID TEA-LEAF.

JAVA TEA-LEAF.

SKELETON OF GENUINE TEA-LEAF.

But in order to better detect the presence of spurious leaves in tea a keener knowledge of the botanical formation of the true tea-leaf is requisite, for which purpose the use of a microscope will be found an invaluable aid. Tea-leaves in general construction bear a strong resemblance to those of the willow and many other plants of the kind, vary widely in size and form, being much smaller, more deeply serrated, and ending more regularly just short of the stalk. The venations are very characteristic, the veins running out from the middle rib, almost parallel with each other, altering their course before reaching the extremities, and turning so as to leave a bare space within the border. When infused and unfolded it is of a bright-green color, the loopings together of the principal veinings in the true leaf being very characteristic. While the spurious leaf is either of a greenish-yellow or reddish-brown color, and irregular in form under the same conditions or when deprived of its cosmetics.

To still better distinguish between them treat a sample of the suspected tea as in making an ordinary infusion to soften and expand the leaves, then separate and uncurl them and lay flat on a piece of glass or other smooth surface for comparison with the genuine leaf. Next see that they agree in description and formation, but more especially in the venations and serrations. Or soak the leaves in hot water, and carefully unroll and closely examine their formation and structure and then compare closely. The epidermis of the lower surface of the true leaf can be with a little caution detached in small portions with a sharp razor, and then analyze the frame or skeleton of the leaf in a little water or glycerine, under a microscope, comparing the venations and serrations with those of the genuine tea-leaf. Still another simple and inexpensive test is to boil a few of the suspected leaves for a minute or two on a watch glass, with a little distilled water, and add an equal portion of burnt magnesia, treating the whole until it is reduced to a large-sized drop. If no crystalline sublimate is obtained therefrom by the operation the leaves cannot be those of genuine tea.

Chemically an examination of the ash of tea-leaves also affords some criteria which may also be utilized for the purpose of identifying the true tea-leaf. For instance, in common kinds of wood, such as oak, deal and pine, the proportion of ash is a few-tenths per cent. of the whole, and by taking wood in its ordinary air-dried condition it contains some 20 to 30 per cent. of moisture. Leaves, on the other hand, contain 10, 20 and even 30 times as much mineral matter, there being doubtless a connection between this abundance of mineral matter and the active chemical changes which take place in the leaves during the growth of the plant. In tea-leaves, therefore, as in leaves in general, the ash amounts to aconsiderable percentage, usually averaging about 6 per cent., so that a chemical examination of the ash forms an important part of the analysis of tea. The proportion of ash in all teas is tolerably constant, genuine tea rarely yielding so little as 5 and never exceeding 6 per cent. of ash on incineration. Therefore, to determine the amount of ash, weigh a small quantity of the tea in its ordinary commercial state and burn it in a platinum crucible and then re-weigh the resultant ash; by observing a few simple precautions very constant and accurate results are attainable by this method. The crucible should be clean and bright, the lid fitting precisely; an iron triangle, covered with a tobacco pipe may be employed to support the crucible during ignition. The operation is then commenced by igniting the empty crucible, and allowing it to cool, being placed for that purpose on a piece of porcelain or iron, immediately weighing the crucible on becoming cold. Next place one or two grams of tea in the crucible, weighing both together, and ignite over a spirit lamp or good gas-burner, stirring the contents with a platinum wire for a few minutes. When ignition is complete the crucible is covered with the lid, let cool again and immediately weighed a second time. If there is any doubt as to the completeness of the ignition, the crucible must be again ignited, and if there is no difference in weight, the ignition is thereby proved finished. As is obvious, in order to obtain accurate results it is indispensable that the crucible should be in the same condition when it is weighed empty and when weighed with the ash, and this is insured by the preliminary ignition and rapid re-weighing, as above described.

The following determinations of the percentages of ash in spurious leaves most used in the adulteration oftea, dried after the manner of tea, may serve to illustrate, the leaves being gathered towards the end of August:—

To these may be appended the determinations of Paraguay tea at 28 and the ordinary tea of commerce at 5.92 per cent.; while in Peligot’s analysis the average proportions of ash in true tea-leaves is given as follows:—

Proving, as has been mentioned, that genuine tea-leaves as brought direct from the producing countries, or such as is a fair commercial article, does not yield less than 5, or sensibly more than 6 per cent. of ash on incineration. When the ash much exceeds 6 per cent. the first question to be considered is whether it is accidental or if the high yield of ash would be maintained if a larger quantity of the sample were incinerated. The composition of the ash of genuine tea-leaves has also been carefully studied, yielding on analysis the following constituents:—

This analysis is especially important, inasmuch as the tea which furnished the ash was of guaranteed purity, so that no question of the possibility of its sophistication could arise. On examining this analysis it will be observed that tea-ash contains a quantity of iron, also some manganese, the presence of manganese being so marked in tea-ash that on subsequent treatment of the ash with water a deep-green solution of manganate is obtained. Owing to this presence of manganese in tea-ash it also invariably evolves chlorine very perceptibly when it is treated with hydrochloric acid.

If the analysis of the tea-ash is referred to it will be noted that more than one-half of it should be soluble in water, so that for all practical purposes a complete analysis is not requisite, a determination of the ratio ofsolubletoinsolubleparts of the ash being sufficient. Such a determination is made by boiling the ash several times with a little water, filtering and washing the residue in the filter, drying the precipitate, igniting and weighing it. The weight of the insoluble part of the ash may then be subtracted from the weight of the entire ash, in which manner both the percentage of the soluble and insoluble ash will be conveniently arrived at, in which case the following determination of the percentage of “soluble” and “insoluble ash” in 100 parts of spurious leaves and pure tea when completely dried will be of interest here:—

Proving that in spurious leaves the ratio of soluble or insoluble ash is very different from what it is in genuine tea-leaves, and that an ash of such composition cannot be very soluble in water.

Peligot has also pointed out that tea leaves differ from other leaves by their extraordinary richness in nitrogen, the prepared leaf being by the process of curing rendered still more nitrogenous than the raw or spent leaves, the former averaging, according to his experiments, 6 per cent. of nitrogenous matter, and the latter 4.37, so that if the tea-leaf be unique in containing such a high percentage of nitrogen, it is obvious that a determination of nitrogen in tea may also be useful as a method of identification.

The tea-extract also yields a comparatively large quantity of ammonia when it is boiled with potash or permanganate of potash, and it is probable that this characteristic may also prove very valuable in the testing of tea. A solution containing about 10 per cent. of solid potash, free from ammonia and nitrogenous matter is required for the purpose, and easily obtained. So that a deficiency of theine, a deficiency of nitrogen, and a deficiency of ammonia are all indicative of the presence of foreign leaves in tea.

Are principally used in the adulteration of Black teas, and is effected by adding or substituting leaves that have been at least once used, and from which all the vital properties have been extracted. The Chinese being inveterate tea-drinkers, large quantities of these leaves are always to be had for the purpose, they are re-dried and subjected to a treatment of gypsum or terra-japonica, in order to make them retain their curl, and then glazed or “faced” with a preparation composed of either graphite or silica to enhance their appearance in the hand; a decoction obtained from catechu or logwood being next added to impart a tea-like color to the liquor when infused. This vile compound is known to theChinese as “Bastard tea,” and is rarely sold alone, being used principally for mixing or blending with pure teas.

The presence of spent or exhausted leaves in either Green or Black tea is best determined by estimating the amount of tannin contained in the liquor after infusion, and for which experiment various tests are in use. A large proportion of the tea-extract is found to consist of tannin (tannic acid), there being much more in Green than in Black tea, the larger portion of that originally existing in the latter being dissipated by the extra fermentation to which this variety is subjected in curing and firing. Green teas contain on an average about 15 per cent. of tannin, Black teas never exceeding 10 per cent. This rate, however, varies considerably from different causes, such as age, quality, soil and climatic condition of the districts of growth, the main average being 12 and 9 per cent. respectively in pure teas. Spent or exhausted leaves, on the other hand, contain only 2 per cent. on an average at the highest estimate, a difference of 7 to 10 per cent. of tannin, as will be observed, in favor of pure teas.

For the purpose of estimating the percentage of tannin contained in tea, the simplest method is to make an infusion of the leaves and pour it into a cup or glass and add to it a small quantity of a standard solution of plumbic acetate. The acetate will cause the tannin to form a precipitate, which must be removed and weighed in a small scale fitted for the purpose; then by taking the nominal percentage of tannin contained in pure teas at 12 in Green and 10 in Black and 2 per cent. in Spent or exhausted leaves, the difference will be the percentage of adulteration, the extent being indicated by the lessened proportion of tannin in the same ratio. The presence ofCatechu (soluble salts of iron) is best ascertained by making an ordinary infusion of the leaves, allowing the liquor to cool and pouring it into a cup or glass. Next add a preparation of neutral plumbic acid and separate the precipitate formed by the introduction of the chemical by filtration, and adding a little argentic nitrate to the filtrate. If catechu be present the residue will turn a dark-brown, the liquid meanwhile acquiring a deep yellow hue, while under the same conditions the liquor of pure tea will remain unaffected. But if the cosmetic be extensively employed, a weak solution of ferric-chloride will cause the precipitate to turn light-green or it may be detected under the microscope if heavily coated.

Spent and spurious leaves may also be readily detected by the “ash test,” through the following deductions: Pure teas, as shown above, contain from 5 to 6 per cent. of ash on incineration, 2 per cent. of this being soluble in boiling water; any increase of these parts is a certain indication of the presence of foreign or exhausted leaves in the sample treated. The percentage of ash contained in spent leaves, ranging from 10 to 30, and in spurious leaves from 40 to 50, in many instances, while the residue of teas adulterated with mineral matter have been known to reach as high as 75 to 80 per cent. of the incinerated sample. The presence of logwood is best exposed by the addition of a few drops of sulphuric acid to an infusion made with the leaves in the ordinary way. If any of the dye be present this acid will cause the liquid to turn a deep red, but if the tea be uncolored the liquor will remain entirely unaffected. Graphite being visible to the naked eye is easily distinguished by its characteristic glossy nature, or can be separated by treating the leaves with boiling water in the usual manner and evaporating the infusion. The substance, if present, will form adeposit at the bottom of the vessel or will be found adhering to its sides if used in large quantities. While Silica is readily recognized by the increased amount of ash insoluble in the water obtained by calcimining a sample of the tea so adulterated, as above described.

Is frequently introduced into tea with the object of adding weight, and is best detected by the “ash-test.” As formerly stated, the leaves of genuine tea, or tea of fair commercial value, yield from 5 to 6 per cent. of ash or mineral matter on incineration, 2 per cent. of which is again soluble in water. This rate is fairly constant, and ranges from 5 in Black teas to 6 per cent. in pure Green, rarely yielding as low as 5 in the former and never exceeding 6 in the latter, while many of the teas of commerce are found to yield from 13 to 20 per cent. of ash on incineration. Such teas are unmistakably sophisticated, and will be found, on analysis, to contain sand or other mineral matter in their composition.

To determine the amount of mineral matter contained in teas so adulterated, proceed as in the case of spurious and spent leaves, which analysis may be again confirmed by a determination of the ratio of soluble to insoluble matter contained in the ash. The result is obtained by boiling the ash in a little water and filtering the precipitate, drying, burning, weighing and subtracting the residue or insoluble matter from the original weight of the ash. By this process both the soluble and insoluble parts are ascertained, and if the sample be pure, but 3 to 3½ per cent. of insoluble will remain, any increase of these figures clearly denoting adulteration to that extent.

Where the burning of the leaves is inconvenient, the following operation may be substituted: Weigh a sampleof the suspected tea and boil with about ten times its weight of water in a porcelain dish or beaker. This boiling will wash the sand off the leaves and sink to the bottom, the leaves floating in the liquid. When the liquid has cooled sufficiently, the leaves may be removed with the hand, the liquid and sand being poured into a filter. The sand is then washed, dried and ignited in a platinum plate and weighed, in which manner the amount of sand yielded by 50 or 100 grams of tea may be actually weighed and ascertained. On examining the analysis it will be found that tea-ash contains a quantity of iron and some manganese, the presence of the latter being so marked in tea-ash, that on subsequent treatment of the ash with water a deep green solution of the manganate is obtained. Owing to the presence of this chemical, tea-ash also evolves chlorine very perceptibly, particularly when treated with hydrochloric acid. If the sample of tea treated yieldonlythe normal percentage of ash at the same time contains a considerable quantity of silica, such a combination would afford the strongest evidence of adulteration. This will be apparent from the fact that tea-ash is an essential part of the tea, and if a part of the tea-ash be absent, the sample must have been deprived of at least the corresponding quantity of tea. Spent leaves contain less ash than genuine tea, the average being about 3.06 of ash in 100 parts of dried spent leaves, and when the ash is deficient, the explanation is that the genuine tea has been more or less replaced by spent or exhausted leaves. But for all practical purposes a complete analysis of tea-ash is not necessary, a determination of the ratio of soluble to insoluble portions of the ash answering the purpose as well. Such a determination is made by boiling the ash several times with a little water, filtering and washing the precipitate in thefilter, drying, igniting and weighing it. The weight of the insoluble part of the ash may then be subtracted from the original quantity, in which manner the percentage of soluble and insoluble ash is obtained.

Peligot has also pointed out that tea-leaves differ from the leaves of other plants by their extraordinary richness in nitrogen, the percentage averaging 4.37 per cent. in the raw leaf of the former, and ranging from 5.10 to 6.60 per cent. in the dried state. In the preparation of the fresh leaves for market a quantity of juice is expressed from them, the increase of nitrogen in the prepared leaf being accounted for on the supposition that this juice is not as rich in nitrogen as that still remaining in the leaf, and if the prepared leaf be unique in containing this high percentage of nitrogen, it is obvious that a determination of nitrogen in tea may prove useful as a method of identification.

Are best detected by pulverizing a sample of the suspected tea and spreading the powder on a piece of glass or plate, and applying a magnet to the dust. If a quantity of the particles gravitate and adhere to it, the tea is undoubtedly adulterated in this form. While fabrications and sophistications in general may be best exposed by treating an infusion of the leaves with a watery solution of sulphuretted hydrogen or a weak solution of ammonia. Under the first treatment the liquor of pure teas will retain its natural color, but will assume a light-blue tint under the latter.

Another simpler method for those who may not have the chemicals or appliances convenient is to place a small quantity of tea-leaves in a wine-glass or goblet, pour on cold water, and stir or shake well for a few minutes. The tea, if pure, will only slightly color thewater, but if adulterated, a dark-colored liquor is quickly yielded, which if boiled and let stand until cold will, if spurious, become bitter and almost transparent as it cools, while pure tea under the same conditions assumes a darker color and pleasing flavor. The latter changes arise from the tannin (a natural property in tea) of which artificial tea is entirely devoid and adulterated teas in proportion. Mineral adulterants, however, must be dealt with by the ash-test, which is unerring, spurious leaves by their botanical character and structural marks, deficiency of tannin being invariably an indication of spent or exhausted leaves.

The part of the tea which we really use being that which passes into the infusion, in other words—the Extract of tea—it is natural to look to this extract as affording the directest evidence of the quality and genuineness of a sample of tea. The extract may be regarded bothquantitatively and qualitatively, and from the former point of view we are led to the tea-assay or determination of the weight of the tea-extract which a given weight of tea is capable of yielding.

In Peligot’s analyses we find the following determinations of the tea-extract—the author being quite alive to the importance of such a test:—

These results being arrived at by the employment of a valid but rather inconvenient method of weighing out ten grams of tea-leaves and boiling them with water as long as anything is dissolved out of them, and afterwards drying up the exhausted leaves, first at a low temperature and then at a higher one, finally weighing the exhausted leaves. The loss in weight is the weight of the tea-extract, care being taken to weigh the original tea and the exhausted tea-leaves in the same state of dryness. The results, as will be observed, are stated both in the dried tea and in the tea in its ordinary commercial condition. But, instead of weighing the tea-leaves before and after extraction and taking the difference in weight as the weight of the extract there is a more convenient process—that of evaporating down the extract itself to dryness and weighingit. The drying up of the exhausted leaves and the getting them into the same hygroscopic condition as the original tea presenting considerable practical difficulties.

The evaporation of the infusion to dryness and the weighing of the dry extract is also a tedious process in its unmodified state. But if a given quantity of tea be boiled with successive portions of water no more tea-extract is yielded than if the same tea be boiled once with a large quantity of water, but whether the infusion is kept for a length of time just at the boiling-point or whether it be made to boil vigorously makes some difference in the result, brisk-boiling extracting about one-tenth more than slow boiling, so that if the boiling be very vigorous half an hour’s boiling is just as effective as an hour’s slow boiling.

Founded on these observations an assay of the tea-extract may be made by the following simple process: Put ten grams of tea into a pint flask and pour on abouttwo-thirds of distilled water accurately measured, a cork and bent tube is then adapted to the mouth of the flask and a connection made with a condenser. The contents of the flask are next heated and made to boil strongly. That having been done the boiling is stopped and the flask and condenser disconnected and the distillate poured back into the flask and the decoction of tea observed closely. If quite clear fifty grams are weighed out and evaporated to dryness in a water-bath and weighed till constant. If the decoction be not quite clear by this time it is to be filtered hot; the first small filtrate is best thrown away and the filtrate collected, weighed, and dried in the water-bath until the residual tea-extract becomes quite constant. Having performed the operation in the manner directed, the weight of the tea-extract actually weighed will be the weight of the extract yielded by one gram of the sample to be assayed.

But in coming to a decision as to the genuineness of a sample of tea of which an analysis has been made by this method, it is of importance to remember that genuine tea is subject to considerable variation in composition. The quality and condition of the leaf at the time of gathering and the different treatments which it undergoes in the process of manufacture, or whether the tea is Black or Green, cause the composition to exhibit a wide range of variation. Taking the percentage of the extract as a basis from which to start, that in genuine tea being from 32 up to 50 per cent. in its ordinary commercial condition. Such being the case, it is obvious that a determination of the percentage of extract will not enable the expert or analyst to say whether the sample of tea be of a lower or higher grade of pure tea, or whether it is composed of a high grade of genuine tea and a portion of exhausted leaves. In a general way,however, this question is not of vital importance to the analyst, as a solution may be arrived at from a determination of the soluble ash, which would be found rather deficient on incineration. For although tea may be exceptionally rich in extract, and although there are difficulties in the way of deciding whether a given sample of tea consists of average quality or of fine tea mixed with spent tea, there are no such difficulties in recognizing the case of tea of average grade, mixed with a considerable quantity of exhausted leaves, as it is assumed in this formula that the soluble ash in genuine tea is 3.6 per cent. and that in spent tea only 0.3 per cent. But in using this formula it must be understood that the results are only rough approximations, judgment and discrimination being required to determine by it.

Tea-extract yields a comparatively large quantity of ammonia when it is boiled with potash and permanganate of potash, and it is probable that this character may prove very valuable also in testing the purity of tea, for which purpose a solution containing about 10 per cent. of solid potash, free from ammonia and nitrogenous matter, is required and easily obtained. Ten grams of this solution of potash is put into a small flask-retort, working in an oil-bath and connected with a small condenser; the whole apparatus to be carefully freed from the last traces of ammonia, which is best accomplished by distilling the water through it, after which from 5 to 10 parts of the tea infusion are poured into the retort, which is then corked up and heated in an oil-bath to 150 C. Having been maintained for a short time at this temperature it is then lifted out of the bath and some pure water poured into the retort, which is again to be heated in the oil-bath. More than half of the water is then distilled over and in this manner the “free ammonia” is obtainedfrom the distillate. When this has been accomplished some of the potash and permanganate solution is added to the contents of the retort and distilled so as to yield a distillate containing “albuminoid ammonia,” the result being as follows in pure teas:—

While the extract from a sample of spurious leaves yielded of

This experiment is made with the greatest ease, and will also be found valuable by brokers and others interested in tea for testing the strength of the tea-infusion. As has already been observed, tea is also remarkably rich in nitrogen, so much so that a determination of nitrogen may be resorted to as a means of identification. With this object it is best to take a sample of tea, first mixing it up well and powder it in a mortar. Of this tea-powder some 0.3 grams should be accurately weighed out. This is then to be mixed with some 50 grams of oxide of copper, which has been first oxidized without the employment of nitric acid, and which shortly before using had been ignited and allowed to cool. A combustion-tube of hard German glass, closed at one end and perfectly clean, is next charged as follows: At the closed end a layer, some three to four inches in length, of a mixture of dry bi-carbonate of soda and fused bi-chromate of potash is placed, the mixture being intended to give out carbonic acid. Next to this compound place two inches of oxide of copper, then the mixture of tea and oxide of copper,then more oxide of copper and some clean metallic copper on top, then a perforated cork and exit tube, which dips under the mercury, and place the combustion-tube in an appropriate furnace to heat. By heating the layer of carbonate of soda and bi-chromate of potash, carbonic acid is caused to traverse the tube and expel the air from it. This having been done the tube is next heated gradually from before so as to burn up the tea, the gases being collected over the mercury. At the end of the operation the carbonic acid is once more made to traverse the tube by again heating the mixture at the back, all the nitrogen being driven from the tube and collected. Finally the carbonic acid is absorbed by means of the potash and, the residual nitrogen gas is measured with well-known precautions. This gas should also be tested for bin-oxide of nitrogen by means of oxygen and pyro-galate of potash, any bin-oxide of nitrogen gas to be measured and allowed for in the test.

Among the most common forms of adulteration practiced by dealers in this country is that of substituting old and valueless Young Hysons for Japans or mixing them together the better to disguise the fraud. The mixing or blending of old, stale, weedy or smoky Congous with Oolongs, particularly when such teas become a drug on the market. The reduction of Moyunes by the addition of Pingsueys in the proportions of half and half and then refacing them as “True Moyunes.” The refacing of Ningyongs and other Amoys as Formosas being still another form, for which at the present low prices of the commodity there is not the slightest occasion. The most recent “trick” of the tea trade being that of mixing Japan Nibs with Twankays and Hysons, the latter, I regret to add, being now extensively adopted by at one time reputable houses.

Some law should be passed in this country to ensure the public against the possibility of purchasing spurious and adulterated teas as in Russia, where the dealers are compelled to sell their teas under government labels placed on the packages by experts appointed by the Government for that particular purpose and who work under official inspectors, the expense of examining and labeling being defrayed out of the revenue realized from the sale of the labels to the dealers. To such an extent was the nefarious practice carried on in that country that the adoption of this system became imperative in order to restore the confidence of the public in the genuineness of the tea offered for sale, with the result of having materially checked the traffic in spurious and adulteratedteas in that country.

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