186 ANILINE-VIOLET 



attraction for this colouring-matter. The fixation of the colour on cotton can there- 

 fore only bo effected by first treating the cotton -with some animal mordant, or with 

 tannic acid. 



There are two modes of proceeding for this purpose : 



1. The fabric is printed with the thickened organic mordant ; for goods intended to 

 be dyed throughout tho mordant is uniformly spread on tho whole surface of the stuff, 

 and fixed either by drying or steaming before tho fabrics are introduced into the dye- 

 bath. The colour is only fixed on the mordanted portions, and the shades themselves 

 may be varied according to the nature and composition of tho mordant. 



Among the substances employed as organic mordants for rosaniline are : Albu- 

 men, whether made from white of egg or from blood ; prepared gluten, prepared casein, 

 gelatine, and tannin this latter being used either in its combinations with tho 

 metallic oxides (as antimonic, stannic, or plumbic), or as tannato of gelatine. For 

 some time oily preparations were employed, as, for example, the sulphomargaric and 

 sulpholeic acids. 



2. The mordant is thickened, and at tho same time some aniline-red is dissolved in 

 it ; the stuff is printed therewith, dried, and steamed ; the whole is then fixed on the 

 fabric, which then has only to be washed and dried. 



This method is principally employed when using albumen, in which acetate of ros- 

 anilino is dissolved. Latterly tannin has been employed in preference for fixing 

 aniline-red, particularly in dyeing ordinary articles ; for the mordanting of which 

 albumen, although giving the most satisfactory results, is too costly an article. 



It is to Mr. Perkin that we are indebted for the first application of tannin for fixing 

 aniline colours upon cotton. 



MM. Kuhlmann and Lightfoot have called attention to the advantages presented 

 by the use of tannate of gelatine ; and Mr. Walter Crum has minutely indicated the 

 treatment by which gluten, the cheapest substitute for albumen, may bo rendered 

 available in printing and dyeing with aniline colours. 



AMTXXiXirxi-VXOXiET. To this colour in its varieties the names of Mauve, Ani- 

 leine, Indisine, Phenameine, Violine, Bosolane, Tyroline, &c. have been given. Mr. 

 Perkin's patent dates from 26th August, 1856, and this was tho original of all 

 the numerous colorific compounds commercially produced; Aniline-violet was first 

 obtained in the crystalline condition in 1860 by M. Scheurer-Kestner, who used mono- 

 hydrated acetic acid as a solvent. Dr. Hofmann informs us that in 1862 Kestner 

 obtained ' splendid well-developed prisms of perfectly pure aniline-violet, which that 

 chemist produced by operating on a very large scale.' The chemical composition of' 

 this colour has not yet been definitely established, but the aniline-purple prepared by 

 Perkin's process is the sulphate of a base called Mauveine, having the composition 

 C 27 H 2I N 4 . The process of manufacture is as follows : A cold and dilute solution of 

 sulphate or any other salt of commercial aniline is mixed with a solution, also cold 

 and dilute, of bichromate of potash. The mixture is well stirred, and allowed to 

 stand for ten or twelve hours. A black precipitate is produced, which is collected 

 upon a filter, washed with cold water, and dried. The black matter is digested with 

 light coal-tar oil, when a brownish-black tarry substance is dissolved from tho 

 colouring-matter obtained in the precipitate. The insoluble residue is then dried and 

 digested with wood-spirit or alcohol, or indeed with any liquid capable of dissolving 

 the colouring-matter. The clear solution is separated by filtration or docantation, and 

 distilled in order to recover the alcohol or wood-spirit ; the residue left in the retort 

 is Mr. Perkin's aniline-violet. 



Tho black precipitate, after having been washed with cold water, is extracted by a 

 prolonged ebullition with large quantities of water (sometimes acidulated with from 

 one to two per cent, of acetic acid), an operation which effects the solution of tho 

 colouring-matter. The filtered solutions are concentrated as much as possible, and 

 while boiling are precipitated by the addition of caustic soda. The precipitate is 

 filtered off and washed for some time with an alkaline solution, which facilitates the 

 extraction of the excess of bichromate of potash, and removes a reddish colouring- 

 matter affecting the purity of the aniline-violet. It is then treated with cold water 

 until the alkali is removed, and the washings become coloured. The violet is thus 

 obtained in the form of a paste. 



The following processes have also been proposed for tho production of aniline-violet : 



1. Oxidation of an aniline salt by a solution of permanganate of potassium. 

 Williams. 



2. Oxidation of an aniline salt by a solution of ferricyanide of potassium. Smith. 



3. Oxidation of a cold and dilute solution of hydrochlorato of aniline by a dilute 

 solution of chloride of lime. Bolley, Beale, and Kirkman. 



4. Oxidation of a salt of aniline in an aqueous solution by peroxide of manganese. 

 Kay. 



