ANILINE-BLUE 181 



mixture of 2 kilogrammes of dry hydrochlorate of rosaniline and 4 kilogrammes of 

 aniline be employed, the operation is completed in four hours. The crude blue is 

 purified, by treating it successively with boiling water, acidulated with hydrochloric 

 acid, and with pure water, until it presents the purest possible hue. Mr. Nicholson 

 has devised and patented a process of purifying the blue colouring-matter, which he 

 dissolves for this purpose in concentrated sulphuric acid, afterwards digesting the 

 solution for half an hour at a temperature of 150 C. On adding water to this 

 solution, the blue colouring-matter is precipitated in a modified condition, having, in 

 fact, become soluble in pure water. 



Dr. Hofmann has determined the nature of aniline-blue, which he thus describes : 

 The blue colouring-matters, as might have been expected, are saline compounds 

 of a colourless base, which may be obtained in a state of perfect purity by dissolving 

 one of the salts (the hydrochlorate, for instance) in alcohol, and filtering the solution 

 into alcoholic ammonia. The deep blue immediately disappears, and the slightly 

 reddish solution yields the free base on addition of water, in the form of a white 

 curdy precipitate, which gradually assumes an indistinctly crystalline character. 

 Dried in vacua, this substance remains colourless, or assumes a slightly bluish tint ; 

 at 100 it cakes, and becomes brown ; and is found by analysis to contain 



C 38 H S1 N 3 , H 2 0. 



This formula exhibits an extremely simple relation between aniline-blue and aniline- 

 red ; indeed, aniline-blue is triphenylic rosaniline : 



Aniline-red C 2ffl H 19 N S ,H 2 Kosaniline. 



Aniline-blue C-f?" 1 N s , IP /Triphenylic 



\Eosamhne. 



The salts of the triphenylic derivative correspond to the rosaniline salts. The 

 composition of the hydrochlorate, which Mr. Nicholson prepared in a state of perfect 

 purity, is analogous to that of the monacid hydrochlorate of rosaniline : 



Hydrochlorate of rosaniline C 20 H 19 N 8 , HC1. 



r-TTjg T 



Hydrochlorate of triphenylic rosaniline C 20 QQSTTS N 3 ,HC1. 

 The genesis of aniline-blue is represented by the following equation : 



C 20 H 19 N S ,HC1 + 3 P 8 ^} N "I = C 20 f'S'.Hivi 1 N'.HCl + 3H 8 N. 



Hydrochlorate of Aniline Hydrochlorate of 



Rosaniline Triphenylic 



Kosaniline. 



Aniline-blue, when submitted to the action of reducing agents, such as nascent 

 hydrogen or sulphide of ammonium, is converted into a colourless, difficultly crys- 

 tallisable substance, which in composition corresponds to leucaniline. It contains 

 C 38 H 33 N 3 .' 



The recognition of the nature of aniline-blue led Dr. Hofmann to some experiments 

 which soon became of great industrial importance. Seeing that the substitution of 

 three atoms of phenyl for three atoms of hydrogen in rosaniline induces a change 

 from red to blue, the idea naturally suggested itself to replace the hydrogen by other 

 radicals, such as methyl, ethyl, and amyl. Experiment furnished results of much 

 interest. Kosaniline is readily attacked by the iodides of these radicals : a series of new 

 substances being produced, obviously the salts of trimethyl, triethyl, andtriamyl rosani- 

 line, the blue and violet colours of which are similar to that of the phenylated com- 

 pound. These new colouring-matters are now manufactured on a largo scale by Messrs. 

 Brooke, Simpson, and Spiller, of London. 



Under the title of ' Improvements in preparing Colouring-Matters for Dyeing and 

 Printing,' Dr. Hofmann patented (sealed August 29th, 1863) the following processes : 

 ' I take the substance now well known as " rosanilino," being the base obtained from the 

 various salts of rosaniline found in commerce under the names of ' ' .roseine," ' ' magenta," 

 and also by other names, and which is usually prepared from aniline and the homo- 

 loguos thereof, and I mix it with the iodides, bromides, or other salts of the "alcohol 

 radicals," such as iodide of ethyl, methyl, or amyl, or bromides of the same. I em- 

 ploy the substances, by preference, in the proportion of one equivalent of rosaniline 

 to three equivalents of the salt of the alcohol radical ; I then heat the mixture, either 

 .alone or together with methylated spirit, to a temperature between 212 and 300 Ft 



