182 A1TCLINE-GREEN 



in a close vessel under pressure ; it is convenient to use an iron boiler provided -with 

 a safety-valve. I continue the heat until the desired result is obtained. During the 

 heating the mixture passes through several phases of colouration, being eventually con- 

 verted into a blue substance. If the process is stopped before the whole is converted 

 into the blue, the mixture is then of a violet or purple colour. For the purpose of 

 dyeing and printing the mixture may be used in the same manner as that in which the 

 aniline colours are employed.' 



Nicholson's method of making aniline-blue soluble in water was discovered in 1862, 

 but other soluble aniline-blues are now in the market. Sulphuric acid acting upon 

 aniline-blue can give a series of products varying according to the intensity of the re- 

 action. All are sulphacids of triphenylrosaniline. Bulk has proved the existence of 

 four of these bodies. Sulphuric acid gives, according to circumstances, sulphate of 

 triphenylrosaniline, or its mono- bi- tri- or totra-sulphuric acid. When we treat 

 hydrochlorate of triphenylrosaniline with strong sulphuric acid and cool the mixture, 

 we obtain a deep red liquor, and hydrochloric acid is liberated. On putting this mix- 

 ture into water, sulphate of triphenylrosaniline is precipitated unaltered in tho form of 

 a fine blue powder. If, instead of cooling the mixture, it is heated and kept for five 

 or six hours at a temperature of 30 0., it yields equally, when poured into water, a 

 blue precipitate, insoluble in that liquid, but which differs from the last-mentioned 

 blue precipitate in being soluble in a solution of soda, in which it gives a red solution. 

 This latter precipitate is the monosulphuric compound of aniline-blue. When re- 

 cently prepared, itforms deep blue masses, which, when dried in the water-bath, take 

 a fine metallic lustre. It is a monobasic acid, forming with the alkalies salts soluble 

 in water ; those of the earths are sparingly soluble. To obtain these salts it is need- 

 ful to treat the freshly-prepared acids with caustic alkalies. They are scarcely 

 soluble in cold water, and dissolve in hot water with a feeble colouration. The soda 

 salt of this acid is known in commerce as Nicholson's or alkali-blue. It is prepared 

 by digesting the monosulphuric acid of triphenylrosaniline with a solution of caustic 

 soda, not enough to saturate the acid. It is then filtered and evaporated down to dry- 

 ness at 100 C. It is an amorphous black-grey mass. It dissolves in hot water with 

 a blue colour. The colour of the aqueous solutions of the salts in question is very 

 feeble, but becomes strong if the acid is set free. If acetic acid is used the colour 

 is unalterable by air in the cold. It is decomposed by hot acetic acid and by cold 

 mineral acids. Wool extracts these salts from their solutions in a colourless state 

 if borax or silicate of soda is added. The salt thus fixed on the wool adheres 

 very firmly, and cannot be removed by washing. When the wool is plunged into an 

 acid bath, the colour appears in its full beauty and intensity. The bisulphuric com- 

 pound is formed by dissolving the aniKne-blue in six times its volume of sulphuric 

 acid, and keeping it for five hours at 60 C. It is then poured into water. The 

 greater part is precipitated, but a little remains dissolved, forming a blue liquid. 

 The blue precipitate is bisulphuric acid, and the liquid is the trisulphuric. The bi- 

 sulphuric compound is scarcely soluble in water, but dissolves in alkalis forming salts 

 soluble in cold water. The soda-salt is known in commerce as ' soluble blue.' It is 

 more soluble than the soda-salt of the former acid. The salts of the heavy metals 

 are mostly insoluble. The trisulphuric acid is prepared by decomposing the blue 

 liquid formed along with the bisulphuric, by means of hydrochloric acid. The preci- 

 pitate is soluble in water and in alcohol. The highest compound, the tetrasulphuric, 

 is formed by digesting aniline-blue in fuming sulphuric acid at 140 C. The liquid, 

 when poured into water, forms a blue solution, from which the free sulphuric acid 

 may be withdrawn by means of carbonate of lead. On filtering and evaporating we 

 obtain a salt of lead saturated with the tetra-acid. It is soluble in water, and preci- 

 pitable by alcohol. Its alkaline salts are soluble in water and in excess of alcohol. 

 Those of the heavy metals are soluble in water, but not in alcohol. Silk scarcely 

 withdraws the colour from alkaline and neutral solutions of this acid, but is readily 

 dyed in an acidulated bath. The sulphuric compounds of aniline-violet are analogous, 

 but as their colours are not fine, they are loss interesting. 



ANILINE-GREEN. Aniline assumes a beautiful indigo-blue colour by the 

 action of chlorate of potash, to which a quantity of hydrochloric acid has been 

 added, and also under the influence of a solution of chlorous acid. Dr. Grace Calvort 

 and Messrs. Lowe and Clift have produced similar blues, and described them under 

 the name of Azurine. Most of these blues possess the property of acquiring, under the 

 influence of acids, a green tint called Emeraldine. Dr. Calvert obtains this colour 

 directly upon cloth by printing with a mixture of an aniline salt and chlorate of potash, 

 and allowing it to dry. In about twelve hours the green colour is developed. 

 This colour may be converted into blue by being passed through a hot dilute alkaline 

 solution, or through a bath of boiling soap. See VEEDINE. 

 - In the process of forming the bluer shades of ethylated violet by Hofmann's patent, 



