On the Colouring Matters produced from Aniline* 549 



obtained by such able observers to the extreme difficulty of procuring 

 the colouring matter in a state of purity, and to the circumstance 

 that the slightest contamination with other bodies is capable of alto- 

 gether masking the properties of this remarkable compound. 



The red colouring matter of aniline and its saline compounds have 

 been obtained for the first time in the state of purity by my friend 

 and former pupil Mr. Edward Chambers Nicholson, a chemical 

 manufacturer equally distinguished for his scientific attainments as 

 for the skill and indomitable energy with which in many instances 

 he has succeeded in rendering the results of purely scientific in- 

 quiries available for the purposes of life. 



Mr. Nicholson has, with the utmost liberality, placed at my dis- 

 posal not only a very considerable supply of the beautiful compounds 

 which he produces, but also the vast and precise information which 

 in his protracted experiments upon this subject he has accumulated. 

 It is entirely through the kindness of Mr. Nicholson that I was 

 enabled to resume the study of these remarkable bodies, a short 

 account of the composition and of the chemical nature of which I 

 beg leave to submit to the Royal Society. 



Mr. Nicholson designates the pure base of the red colouring matter 

 by the name of Roseine, which appears very appropriate, since this 

 substance, which furnishes such splendidly coloured solutions, is 

 absolutely white in the solid condition. Nevertheless, since the com- 

 pound in question appears to be the prototype of a number of similar 

 substances obtainable by similar processes from the homologues, and 

 probably also from the analogues, of aniline, it may be useful to 

 commemorate the origin of the compound in its name, and I accord- 

 ingly propose the term Rosaniline for the designation of the new 

 substance. 



Rosaniline. — The material from which the base may be most con- 

 veniently obtained is the acetate which in practice is generally used 

 for dyeing. This acetate Mr. Nicholson produces on the large 

 scale in a state of perfect purity. The boiling solution of this salt, 

 when supersaturated with a large excess of ammonia, furnishes a 

 rose-red somewhat crystalline precipitate, which constitutes the base 

 in a tolerably pure state. The colourless liquid filtered off while 

 boiling from this precipitate deposits, on cooling, perfectly white 

 needles and plates, which are the rosaniline in a state of absolute 

 purity. Unfortunately the solubility of rosaniline in boiling ammo- 

 nia, and even in boiling water, is extremely limited, so that only a 

 very small proportion of the compound is obtained in the perfectly 

 white condition. The base is somewhat more soluble in alcohol, the 

 solution having a deep-red colour ; it is insoluble in ether. Exposed 

 to the action of the atmosphere, rosaniline turns rapidly pink, and 

 ultimately dark red. No perceptible alteration of weight is ob- 

 served during this change. At the temperature of 100° the base 

 rapidly loses a minute quantity of water of interposition ; it may 

 then be heated to 130° without further losing weight. At a higher 

 temperature rosaniline is decomposed with evolution of an oily 

 liquid containing much aniline, a quantity of charcoal remaining 

 behind. 



