CHEMICAL SCIENCE. 1SD 



dants ; but the great obstacle to its extensive use was the difficulty 

 of obtaining uric acid in sufficient quantity for its manufacture. 

 The idea soon occurred to chemists to extract it from guano ; and 

 this is the curious source whence the chief supply of uric acid is 

 obtained, and which enables printers to produce the colour called 

 Tyrian purple. 



Another example is adduced in the successive scientific discoveries 

 which have led ir> the discovery of the recently popular colour, 

 Mauve. Lichens, which have been the subject of extensive researches 

 on the part of Eobiquet, Heeren, Sir Robert Kane, Dr. Schunck, 

 and especially of Dr. Stenhouse, have yielded to those chemists 

 several new and colourless organic substances, which, under the 

 influence of air and ammonia, give rise to most brilliant colours, and 

 amongst these are orchil and litmus. Dr. Stenhouse, in a most 

 elaborate paper, published by the Royal Society in 1848, pointed out 

 two important facts : first, that the colour-giving acids could be 

 easily extracted from the weed by macerating it in lime water, from 

 which the colouring matters were easily separated by means of an 

 acid ; and secondly, the properties of certain colouring acids, which 

 gave M. Marnas, of Lyons, the key which enabled him to produce 

 commercially from lichens a fast mauve and purple which, up to 

 1857, had been considered impossible of attainment. 



The commercial production, by Mr. W. H. Perkin, of another 

 purple at the same time is not less interesting. Some thirty or forty 

 years ago, Dr. Runge obtained from coal- tar six substances ; amongst 

 which was one called Kyanol, which substance was thoroughly 

 examined by Dr. W. A. Hofmann, who proved it to be an organic 

 alkaloid, and identical with a substance known by the name of 

 aniline. Owing to the subsequent study of this substance by that 

 eminent chemist, and the discovery that it yielded a beautiful purple 

 colour when placed in contact with bleaching powder, his pupil, 

 Mr. W. H. Perkin, was induced to make experiments, with a view 

 to producing commercially a fast purple, in which he succeeded, and 

 secured it by a patent in 1857. The process devised by this chemist 

 is exceedingly simple. It consists in oxidizing aniline by means of 

 bichromate of potash and sulphuric acid. 



More recently Mr. Renard found a method of producing also from 

 aniline, by means of chlorine compounds, a most splendid rose colour, 

 called by him FucJtsiacine ; and, within the next few months, 

 Mr. David Price also succeeded in producing from aniline, by the 

 employment of peroxide of lead, either a fast purple or a pink, called 

 by him Roseine, and a fast blue, according to the mode of operating. 

 All these colours require special mordants to fix them on calicos or 

 muslins ; Messrs. James Black and Co., and Messrs. Boyd and 

 Hamel, of Glasgow, have fixed the last-mentioned colours by means 

 of azotized principles, such as albumen, lactarine, &c. 



The attention of dyers has within the past year been directed to 

 some new tints which have been brought into the market. The 

 colouring matter for these fine shades is extracted from gas-tar. 

 The French call the colouring matter by the terms Magenta, or 



