(Concluded from p. 204.) THAT species of discharge work we mentioned at the close of our last article is not equally advantageous with other species of dyeing, because it has been found from experience that the colours made in this way are not so fast as those made in the other, and the cloth does not, of course, wash so well. There is another application of indigo, to produce a green, which is well worth mentioning. This consists in printing ground indigo with a solution of tin, (of what nature is not exactly known, as it was a patent invention,) and then fastening the indigo with what is called China blue dipping. The goods are then dyed in bark or weld, which converts the blue to a green, and the whites are cleansed by the ordinary bleaching processes. This mode of dyeing green gives a most beautiful and permanent colour.. The china blue just mentioned is indigo ground fine, then thicken-, ed and printed on the cloth. It is afterwards dissolved and chemically united to the fabric, by alternate immersion in a solution of sulphate of iron and lime water.

Citric acid, or concentrated juice of lemons, is principally employed by dyers and printers to produce white figures on self-coloured grounds, produced by madder and other dyes. The acid is mixed, either with gum or flour paste, to a proper consistency for the block, and wherever it is applied it discharges the mordant and produces a most delicate white. When this acid is used for resist work, it is mixed with clay as well as gum, which gives it a greater body, and acts mechanically in resisting the dyes.

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Aquafortis, or nitro muriatic acid, is the material used for putting yellow figures into blue silk, handkerchiefs. The acid is mixed, with gum, or with flour paste, to a proper consistence, and is then printed of the desired pattern on the coloured silk. Wherever the

acid touches, the colour is discharged, and a yellow produced in its place. The handkerchiefs are then steamed by passing them over a vessel containing boiling water, which adds to the brilliancy of the colour. For producing the spots on cotton bandanas, a different method is employed. Pieces of fine calico, which have been perfectly bleached, are dyed as nearly of a scarlet colour as can be produced on cotton by the common method of dyeing Turkey red, and this colour is afterwards discharged, and the calico restored to its original whiteness. The discharged parts are usually in the form of spots, either square or round; and they are made by a very dilute solution of chloride of lime. The process for effecting this is somewhat ingenious, and we shall describe it a little more at length. To a powerful press, two horizontal plates are adapted, on both of which the pattern to be given to the handkerchiefs is marked. In the under plate holes are cut of the exact size of the pattern, and in the upper plate tubes are strongly cemented of the same size. The tubes of the one plate are made to correspond exactly with the holes of the other. A handkerchief piece doubled ten or twelve times, and of the size of the plates, so that this number of folds of cotton is laid between them, is then laid smoothly over the lower plate. The upper plate is attached to the cover of the press; it is lowered on the cotton, which is closely pressed together by means of the two plates and the mechanic power. The ends of the tubes fixed into the upper plate are thus brought to press on the surface of the cloth with great force, and as each tube has a corresponding hole below, any liquid poured into them penetrates right through perpendicularly, and is not spread over the cloth. When the press is fixed, a very dilute solution of chloride of lime, taining a small proportion of sulphuric acid is poured on the upper plate of the press, which having a rim round it, the fluid can only 1011 01101011 10 9161998

water, thickened with gum, is printed on the cloth, according to the pattern. This same substance, more diluted, forms a mordant for purple, and, still further diluted, forms a lilac in the dyeing copper. Thus all the different shades, from pale lilac, through purple into black, may be produced by the acetate of iron diluted with different proportions of water, and afterwards dyed with madder. In the same way, a colourless solution of acetate of alumina, thickened with gum or flour paste, makes a mordant for dark red; and by diluting it, every shade of red and pink may be produced. And if these two mordants be mixed, a mordant for colours approaching purple or red, as either material predominates, may be obtained. When as many mordants have been printed on the calico as there are to be colours of the above description, they are dried for two days, dunged till the superabundant mordants are removed, washed, and then boiled in a decoction of madder, which single boiling produces all the requisite colours. The cloth is then washed and bleached for a few days, till the whole of the ground to which no mordants had been applied becomes perfectly white. If the goods are to receive yellows, bright olives, or drabs, the same mordants are printed on the remaining white parts, diluted according to the colour to be produced, but instead of being boiled in a decoction of madder, they are to be immersed for about half an hour in a warm decoction of quercitron bark. By substituting the bark for the madder, instead of blacks, pompadours, and reds, we get dark olives, drabs, and yellows, which will vary in intensity according to the strength of the aluminous mordant. Again, if the acetate of alumina be applied to the colours already dyed with the madder before the goods are in immersed in the bark, the reds may be converted into different shades of orange, and the lilacs into cinnamon colours. There different processes enable the calico printer

compounded substance; now it is well known to be a compound substance, and is supposed to consist of one volume of azotic gas and three volumes of hydrogen gas; and, according to the general rules which have been followed in forming the present nomenclature of chemistry, it should receive still another name. On such points, however, a little scientific precision is dearly purchased by that confusion which is always at first occasioned by the introduction of new terms. In the present case, perhaps, this remark is peculiarly applicable, because some chemists suppose that ammonia consists of an unknown base, united to oxygen; and names derived from the constituent elements of substances must of course be changed when ever we are able, by pushing our analysis further, to detect other elementary bodies. Ammonia is used in certain manufactories, and in medicine, and it is a valuable re-agent, or test, to the chemist.

-, Acetate of, spirit of mindererus. A medicine employed as a febrifuge.

, Carbonate of, volatile salis. The substance put in smelling-bottles.

niac.

Muriate of, sal атто

Sulphate of, secret sal ammoniac; vitriolated ammoniac. A salt discovered by Glauber.

AMMONIAC. A vegetable gum, used as a medicine.

fixed, muriate of lime, chloride of calcium. Formerly so b called because obtained from de> composing sal ammoniac by means of lime.

9.1: AMMONIACAL, Salts. All substances formed by the union of an acid and ammonia.

AMMONIUM. The name given by Berzelius to the supposed metallic base of ammonia. DAMMONITES, cornua ammonis; snakeones. These curious substances are petrifactions, and seem to owe their origin to shells of the nautilus kind. They are found of all sizes, and consist chiefly of lime-stone. ShAMNIOS. The liquid contained

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in the uterus of pregnant animals; and which is found to be different in each species of animal.

AMNIOTIC Acid. A peculiar acid, found in this liquid. AMPHIBOLE, hornblende. A mineral extensively diffused. AMPHIBOLITES, trap rocks. Rocks chiefly composed of hornblende.

ANACARDIUM, cashew nut, murking nut. The produce of the cashew-tree; it contains an inflam mable and caustic liquor, very useful for marking on linen or cotton.

ANALYSIS. The resolution of a substance into its constituent parts, for the purpose of examining them; it is not complete unless these parts are discovered and examined. It is distinguished from decomposition by this latter being a more general word, signifying every separation of compound bodies. There is frequently decomposition without analysis, but there can be no analysis without decomposition. Analysis is opposed to synthesis, which is the forming of combinations, and can seldom be effected without synthesis. When we can show the composition of any substance by analysis, and then produce that substance by synthesis, the chemical proof of its nature is complete and perfect.

USEFUL DISCOVERY REWARDED.

THE quantity of iron, employed in the construction of ships has been found to produce so much deviation in the compass as to render it almost a useless instrument in high northern or southern latitudes. Mr. P. Barlow, of the Royal Military Academy, Woolwich, having found a very simple method of remedying this evil, and experience having already demonstrated its efficacy, the Board of Longitude have conferred on him a reward of 5001. His method consists in placing a small plate of iron close abaft the compass, on the principle of counteracting in one direction and one place the effects of all the other iron in the ship. It is found to answer perfectly.