CHEMICAL CHANGES.
Burn some sulphur under the rose, by holding underneath it a lighted bundle of matches. This will fade the red colour, and make the flower turn white or blanched. Its primitive colour will return in about a couple of hours.
Take four glasses; rub one in the inside with a piece of moist alum: let the second have a drop of vinegar in it; the third empty. Let the fourth be filled with clean water; in your mouth put a clean rag, with ground basil tied close in it, the bulk not to be bigger than a small nut, which must lie between your hind teeth and your cheek; then take some of the water that is in the glass into your mouth, and return it into the glass that hath the drop of vinegar in it, which will cause it toturn the perfect colour of sack wine; then turn it in your mouth again, and chew the rag of basil between your teeth, and squirt the liquor into the glass, and it will have the perfect colour of claret; returning the basil into its former place, take the liquor into your mouth again, and presently squirt it into the glass you rubbed with alum, and it will have the perfect colour of mulberry wine.
This name has been given to a beautiful and curious precipitation of silver, by means of mercury in an arborescent form. The experiment is made by putting a soft amalgam of silver into six parts of a solution of nitrate of silver, and four of a solution of nitrate of mercury,or—
Amalgamate in a glass mortar one quarter of an ounce of pure mercury and half an ounce of fine silver. Insert in this amalgamation four ounces of pure nitric acid for the solution, and increase the whole by a pint of distilled water; mix it well, and keep it in a glass decanter well stopped. By introducing into this liquid a lump of soft amalgam of silver, the formation of the tree speedily takes place.
Or, if you wish to make the experiment on a smaller scale, pour about an ounce of the above liquid into a wine-glass, into which insert a piece of soft amalgam of silver, the size of a pea, and the effect required will immediately be produced. The silver, separating in the form of prismatic needles, will arrange itself so as to assume an arborescent appearance.
The precipitation of a solution of acetate of lead by means of a piece of zinc, so as to form what is commonly called the lead tree, is perfectly analogous to this theory, but is too well known to require illustration.
Dissolve iron filings in aqua fortis moderately concentrated, till the acid is saturated; then pour gradually into the solution a solution of fixed alkali, commonlycalled oil of tartar. A strong effervescence will take place, and the iron, instead of falling to the bottom of the vessel, will afterwards rise, so as to cover its sides, forming a multitude of ramifications heaped one upon the other, which will sometimes pass over the edge of the vessel, and extend themselves on the outside, with all the appearance of a plant. If any of the liquor is spilt, it must be carefully collected, and be again put into the vessel, where it will form new ramifications, which will contribute to increase the mass of the vegetation.
In a small globular bottle with a tall neck, dissolve one ounce of fine silver in three ounces of nitric acid; put the bottle into a sand bath, and let it remain over a slow fire till the liquid be half reduced; then add three ounces of good white-wine vinegar, a little warmed; shake the mixture, and place the bottle in any place where it is not likely to be disturbed: in about a month’s time a beautiful metallic fir will appear, ramifying to the very surface of the liquid.
Make an amalgam of a small portion of fine gold, and ten times the quantity of purified cinnabar.
Grind and wash the amalgam in water, till no black colour appears: when perfectly clean, dry the amalgam, and insert it into a glass retort; place it in a sand bath over a slow fire, which must be preserved ignited for a day or two; gradually increase the heat, to expel the mercury from the gold, whose metallic vegetation will be perfectly in proportion to the mercury which escapes. When the fire is extinguished you will find the mercury expelled into the receiver, and the gold remaining in the retort will be soft and malleable, possessing the purest appearance; the mass will have sprouted branches, in perfect imitation of small shrubs and trees of different forms and height, which may be separated from the heap, serving as their base, when taken fromthe retort. These will allow even of being made red hot without injury to their appearance, or fear of decomposition, and may be used as ornaments for any length of time.
For the silver, use the same proportion of metal as for the gold tree.
Sympathetic or secret inks are those fluids which, when written with on paper, are invisible when dry, but acquire colour by heating the paper, or by applying to the invisible writing another chymical agent. These phenomena arrested particularly the attention of the old chymists, and accordingly, in their fanciful way, they called themsympathetic inks.
The writing made with this ink may, therefore, at pleasure be made to become visible or invisible successively, by alternately warming and cooling, if care be taken not to expose the paper to a greater degree of heat than is necessary to make the invisible writing legible.
Put into a mattrass one part of cobalt or zaffree, and four ounces of nitro-muriatic acid. Digest the mixture with a gentle heat until the acid dissolves no more; then add muriatic of soda, equal in quantity to the cobalt employed, and four times as much water as acid, and filter the liquor through paper.
This ink, which may be used like the preceding, is prepared in the following manner. Take one ounce of cobalt reduced to powder, put it into a Florence flask, and pour over it two ounces of pure nitric acid. Expose the mixture to a gentle heat, and, when the cobalt is dissolved, add, by small quantities, a solution of potash, until no more precipitate ensues. Let these precipitates subside: decant the super-natant fluid, and wash the residuum repeatedly in distilled water, until it passes tasteless; then dissolve it in a sufficient quantity of distilled vinegar, by the assistance of a gentle heat, takingcare to have a saturated solution, which will be known by part of the precipitate remaining undissolved after the vinegar has been digested on it for some time.
Neutralize muriatic acid with brown oxide of copper: the solution is of a dark olive-green colour, and by evaporation yields crystals of a grass-green colour of muriate of copper, which, when dissolved in ten parts of water, forms this ink, and may be employed as before stated.
Dissolve cobalt or zaffre in nitric acid, add salt of tartar gradually and in small quantities to avoid too powerful an effervescence, let the precipitate subside, and, having drawn off the super-natant clear liquid, add a sufficient quantity of water, when the ink will be fit for use.
Dissolve zaffre in nitric acid, to which add saltpetre well purified, and you will possess a rose-coloured ink, having the same properties as the preceding.
Write any unimportant matter with common ink, and let the lines be tolerably wide apart; then between these lines write the communication you wish to make with any of the above invisible inks. Your correspondent, by holding the paper before the fire, will be speedily enabled to peruse the letter; the characters will again become invisible when the paper has cooled. The writing in common ink will serve to lull the suspicions of those who might intercept the letter.
With this kind of ink, some very ingenious and amusing tricks may be performed.
Draw a landscape, and delineate the ground, the trunks, and branches of the trees, with the usual water-coloursemployed for that purpose, tracing the grass and trees with sympathetic ink. By these means you will have a drawing, which, at the common temperature of the atmosphere, will represent a winter piece; but if it be exposed to a proper degree of heat, not too strong, you will see the ground covered with verdure, and the trees suddenly wrapped with a beautiful foliage; replace the picture in the cool, and the dreary aspect of winter re-appears. The colours must be lighter for the back grounds.
Screens painted in this manner were formerly made at Paris. Those to whom they were presented, if unacquainted with the artifice, were astonished to find, when they made use of them, that the views they exhibited were totally changed. Persons not understanding drawing may amuse themselves in this manner, by colouring an outlined engraving representing winter, following exactly the process enjoined for the above.
In a middling-sized glass bottle, three parts full of clear water, infuse pure alumine precipitated by ammonia, till the bottle is nearly filled.—Expose the bottle to the cold air in frosty weather; or, at other times, to artificial frost. At the moment when the frigorific effect ensues, the alumine will divide all over the surface of the water, and form itself into separate and very regular strata.
Take eleven drachms of muriate of ammonia, ten of nitrate of potash, and sixteen of sulphate of soda; reduce each of these salts separately to a fine powder, and mix them gradually in a glass, or rather in a thin metal vessel, with five ounces of water (the capacity of the vessel should be only just large enough to hold the materials): the result will be, that, as the salts dissolve, cold will be produced, and a thermometer immersed in the mixture will sink at or below freezing. A little water, about half an ounce, in a test tube, when immersedin the mixture during its solution, becomes frozen in about ten minutes.
The salts employed in this experiment may be recovered from the solution, if the sulphate of soda be omitted, by evaporating the water, to serve again any number of times. Five parts of muriate of ammonia, five of nitre, and eight of sulphate of soda, mixed with sixteen of water, at the usual temperature, sink the thermometer from 50 to about 10 degrees.
The salts, to produce their fullest frigorific effect, should be recently crystallized in fine powder, and contain as much water of crystallization as possible, but they should not be damp.
If to three parts of ice thus procured, you add four parts of potash, the thermometer will sink from 32° to 61° below Zero, or the freezing point; giving 93 degrees of cold. Snow or common ice, mixed with potash in the same proportions, would serve equally well; but the above experiments are given under the supposition that they are difficult to be procured.