ANILINE GREENS .

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by means of common salt and soda crystals ; the filtrate is precipitated withcommon salt, and the precipitate collected and dried. The green prepared inthis manner is generally finer, than that made diredtly from rosaniline.

Crystalline Green.

To obtain the green in a pure crystalline state the crude product is pouredinto a very small quantity of boiling water,—about 60 litres for an operationmade with 5 kilos, of acetate of rosaniline. In separating the green from theviolet, soda crystals are used more freely, even at the risk of destroying a partof the green. The boiling filtrate, on cooling, deposits fine green needles onthe copper rods suspended in the crystallising vat, whilst a crust of less purecrystals settles at the bottom. These crystals are washed slightly with waterand dried.

Aldehyde Green.

This colour was discovered by Cherpin in 1862. Its chemical constitutionis still unknown. Hofmann’s analysis shows it to consist of C22H27N3S2O.For its preparation 1 kilo, of rosaniline is dissolved in 2 kilos, of sulphuricacid, of sp. gr. 1*63, previously mixed with 500 grms. of water. When thesolution is homogeneous, it is mixed with 4 kilos, of a concentrated alcoholicsolution of aldehyde, added in successive portions. The reaction is completein about twenty minutes. The mixture is poured into 25 litres of water, inwhich 4 kilos, of hyposulphite of soda have been previously dissolved. Theliquid is boiled seven or eight'minutes, and filtered. The green is found insolution, and is thrown down by means of tannin, acetate of soda, or a salt ofzinc along with an alkali. The green is washed with water to remove organicsalts, re-dissolved in alcohol, and precipitated with ether. This green yieldsbeautiful shades in dyeing and printing, but is always prepared by the con-sumer when wanted, as it spoils on keeping.

In dyeing with greens sold as insoluble tannates, it is necessary to dissolvein water acidulated with sulphuric acid. In this solution wool and silk aredyed, the former at a higher temperature than the latter.

On wool very full shades may be obtained with iodine green by the followingprocess recommended by Dale. The wool is simply worked in very dilutehypochlorite of lime (bleaching-lime), and is then found to take up the colourvery readily.

The so-called pomona paste of commerce dissolves freely in water withoutalcohol. It is worked upon wool as follows :—A bath of warm water is pre-pared at 158® F., to which silicate of potash is added sufficient to give thewater a greasy feel. In this the wool or woollen yam is worked to saturation.The colour, which has been in the meantime separately dissolved in some coldwater, is now very gradually added to the above bath, the wool being stillworked till a bit taken out—and passed through some water acidulated withacetic acid—shows the right shade. The whole is then taken out and put ina separate bath of water, at 158° F., soured with acetic acid. A little com-mercial tannin or extract of galls may be added to fasten the colour. If theshade is not sufficiently yellow, picric acid is added to the last bath.

Cotton is first well worked in sumach, galls, or myrobalans; then in doublemuriate of tin. It is next rinsed in water, and worked in the colour dissolvedin cold water,