DYEING AND CALICO PRINTING-. 309 



covered in human urine, uric acid. In 1817, Brugnatelli found that 

 nitric acid transformed uric acid into a substance which he called er;/- 

 thric acid, but which was subsequently called by Wohler and Liebig 

 alloxan. In 1818, Dr. Prout found that the latter substance gave, when in 

 contact with ammonia, a beautiful purple-red colour, which he called pur- 

 purate of ammonia — the product known by the name of murexide since 

 the researches of Liebig and Wohler, published about 1837. These dis- 

 coveries remained dormant in the field of pure science until the year 

 1851, when Dr. Saac observed that when alloxan came into contact with 

 the hand, it tinged it red. This led him to infer that alloxan might be 

 employed to dye woollens red, and further experiments convinced him 

 that if woollen cloth were prepared with a salt of tin, passed through 

 a solution of alloxan, and then submitted to a gentle heat, a most 

 beautiful and delicate pink colour resulted. In 1856, MM. Depouilly, 

 Lauth, Meister, Petersen, and Albert Schlumberger, applied it as a dyeing 

 material to silk and wool, and succeeded in obtaining red and purple 

 colours, by mixing the murexide with corrosive sublimate, acetate of 

 soda, and acetic acid. It will naturally be wondered where the supplies 

 of uric acid or murexide could be found to supply such a demand as at one 

 time existed. The production of the colour from uric' acid is in itself 

 interesting, but still more so is the fact that chemical investigation has 

 opened up a source of uric acid so unexpected and so extensive as that 

 of Peruvian guano. To extract uric acid from guano, the latter is 

 treated repeatedly with hydrochloric acid, until all soluble matters are 

 removed by heat and washing. The insoluble mass, consisting chiefly 

 of sand and uric acid, is carefully treated with nitric acid of specific 

 gravity 1.40. When the action of the acid is completed, the mass is 

 treated with warm water, and thrown on a filter. The filtrate, which 

 has a yellowish colour, and contains alloxan, &c, is evaporated carefully 

 to such a degree that when left to cool, it becomes a brownish-red, or 

 violet solid, called by the inventor carmin de pourpre. 



In the French department, M. Charvin, of Lyons, has shown some ' 

 specimens of silk dyed with the interesting green dye extracted by him 

 from the Khamnus catharticus, which is perfectly identical with the 

 curious dye imported from China, and used in this country and in 

 France in 1855 and 1856, kno,vn by the name of La-kao. 



The attention of the public is called to fine specimens of dyed black 

 silk skeins in the English, Prussian, and French departments, bat 

 especially in the latter, where M. Gilet of Lyons exhibits a new black 

 from the substance le Hennee des Arabes, which he imports from Algeria 

 and which he applies with great advantage to obtain a superior weighted 

 black silk. 



With reference to dyed woollen yarns, there are some excellent dis^ 

 plays in the French, Prussian, and Hesse Cassel departments, but the 

 beautiful collection of clouded woollen yarns of M. N. Rave, senior, of 



