232 ANNUAL OF SCIENTIFIC DISCOVERT. 



having for the first time obtained this substance on a larger scale. 

 He produced it by the action of tetrachloride of tin on aniline. Nu- 

 merous other processes were subsequently suggested, among which 

 treatment of aniline with chlorine, or nitrate of mercury with arsenic 

 acjd, and many other substances, may be mentioned. Magenta, often 

 called fuchsine, roseine, etc., soon became an article of large consump- 

 tion. A great impetus to this new branch of industry was given in 

 France by Messrs. Renard and Franc, who were the first to manufac- 

 ture the new article on a commercial scale, and the production has 

 now attained colossal proportions. Before proceeding, however, let 

 me show you the formation of magenta by experiment. Among 

 the many processes which I might adopt for this purpose I select the 

 action of corrosive sublimate upon aniline, not because I consider this 

 process superior to the others, it is, in fact, inferior to many, but 

 because it is, perhaps, the best adapted for a lecture experiment. This 

 white powder is chloride of mercury (corrosive sublimate) ; a small 

 portion of this salt I mix in a test tube with perfectly colorless ani- 

 line. Let us stir the mixture with a glass rod until it is converted 

 into a perfectly homogeneous liquid paste. This paste is still colorless, 

 but on gently heating it by a gas burner it instantaneously assumes 

 a splendid crimson of the greatest intensity, a single drop of the 

 liquid being capable of deeply coloring a large beaker filled with 

 alcohol. 



In all the processes which convert aniline into coloring matters, a 

 considerable number of secondary products are generated, which it is 

 rather difficult to separate from the principal product of the reaction. 

 These difficulties have been most perfectly overcome by Mr. Nichol- 

 son, who has succeeded in obtaining magenta in a state of absolute 

 purity. Chemists have thus been enabled to analyze this substance, 

 and to lift, at all events, the corner of the veil which still covers the 

 mysterious formation of the colored derivatives of aniline. 



In the pure state, magenta is a fine crystalline, and, remarkably 

 enough, perfectly colorless, or only slightly tinted body, which is rep- 

 resented by the formula, 



C 20 H 21 N 3 = C 20 H 19 N 3 , ILO. 



Rosaniline (this is the name by which chemists designate the color- 

 less body) is a base, or ammonia derivative, which forms a series of 

 splendid salts. It is in the state of saline combination that rosani- 

 line acts as a crimson dye. Into this shallow porcelain dish I have 

 thrown a few crystals of rosaniline, which at a distance you scarcely 

 perceive. I now pour upon these crystals a small quantity of acetic 

 acid, when on gently heating the dish the crimson* color instantane- 

 ously appears. But it is only in solution that even the salts of rosan- 

 iline are crimson colored. On slowly evaporating their solution, the 

 red color entirely vanishes, and a splendid green crystalline sub- 

 stance remains, presenting in an extraordinary manner the beautiful 

 metal lustre which distinguishes the wings of the rose beetle. 



Having now explained the several stages of transition through 

 which coal has to pass before it either becomes mauve or magenta, it 

 may be of some interest to you to know the proportion which the 

 finished dye bears to the coal from which it is derived. A set of 



