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were made in France by heating aniline with rosaniline. Hof- 

 mann found that they were derivatives of rosaniline, resulting 

 from the replacement of hydrogen by a compound called 

 phenyl, and that the more the hydrogen was thus replaced, 

 so much the bluer was the colour. In a masterly research 

 Hofmann showed that other groups could be introduced into 

 rosaniline instead of phenyl, and that very beautiful colour- 

 ing matters resulted. The so-called Hofmann violets are of 

 this description, the group introduced in place of the hy- 

 drogen being either methyl or ethyl. Two other colours are 

 produced from rosaniline — one is the so-called gas green or 

 iodine green, and is obtained by the same processes as the Hof- 

 mann violets. The other is a yellow dye called chrysaniline 

 or phosphine, and is found in the residues of the rosaniline 

 manufacture. Other dyes made from aniline have a brown 

 colour, and a very fast black can also be prepared. The lecturer 

 then showed experimentally how easily some of these dyes are 

 prepared, and how simple an operation dyeing silk and wool 

 with them is. In fact, fabrics made of the latter are at once 

 dyed by simply immersing them in a solution of the colouring 

 matter. He then said that the anthracene colours were of great 

 importance, and explained how they were first made artificially. 

 The Egyptians employed madder as a dye, for it has been found in 

 the cloths in which mummies are wrapped. The colouring princi- 

 ple of madder was discovered by two Frenchmen, and was named 

 alizarine by them. Two German chemists showed that alizarine 

 is a derivative of anthracene, a hydrocarbon found in tar, and 

 they then discovered a process for converting anthracene into 

 alizarine. This process was improved by Mr. Perkin, and is 

 now carried out on the large scale. In fact, very little madder 

 is now cultivated, the artificial dye-stuff being employed instead. 

 The lecturer showed what remarkable tinctorial properties ali- 

 zarine possesses, and also dyed some cloths various colours by 

 its means. He expressed his thanks to Messrs. Crum & Co., of 

 Thornlie Bank, near Glasgow, for the beautiful specimens of 

 dyed fabrics they had kindly given him. Dr. Letts then passed 

 on to say a few words about Professor Baeyer's researches on 



