314 MUREXIDE. 



water, to which it communicates a magnificent red colour. This solution 

 not only gives a precipitate with metallic salts, but, when evaporated, yields 

 beautiful crystals, having the iridescent appearance of the wings of 

 cantharides. This discovery has also been useful to medical men, by 

 enabling them to distinguish the uric acid calculi. 



Messrs Liebig and Wohler had also investigated the subject, and suc- 

 ceeded in obtaining from the uric acid contained in the fseces of serpents 

 this substance, which they called murexide, and a new class of organic 

 substances, the knowledge of which has much facilitated the application 

 of murexide to dyeing and printing. M. Saac was the first to apply the 

 products of uric acid to the dyeing of fabrics : his process consisted in 

 dipping woollen fabrics prepared with a salt of tin into a weak solution 

 of alloxan, a product discovered by Liebig and Wohler in heating uric 

 with nitric acid. The fabric so prepared was dried, and when submitted 

 to heat a fine crimson was generated, the intensity of which increased by 

 the fumes of ammonia : but, owing to the difficulty of obtaining a colour 

 of uniform shade, M. Saac's process required improvements, and these have 

 been effected by M. Schlumberger. 



The process followed by Messrs Saac and Schlumberger could not be 

 applied to silk or cotton fabrics. The method of dyeing silk with murexide 

 was discovered by M. de TPouilly, who adopted the following process — viz., 

 dipping the silk in a concentrated solution of bichloride of mercury 

 mixed with murexide, squeezing the silk well and hanging it in the air, 

 when a magnificent crimson insoluble compound was fixed on the silk. 

 This effect is produced from the fact that when solutions of bichloride of 

 mercury and murexide are mixed together, an insoluble compound is only 

 formed after the lapse of an hour or two. 



The process for dyeing cotton is due to Messrs Lauth and Schlumberger, 

 and consists in producing on cotton a purpurate of lead by mordanting 

 with nitrate of lead, passing into an alkali, and then dyeing in a solution 

 of murexide. In order to give a full brilliancy to the colour, it is lastly 

 passed through a weak solution of bichloride of mercury. This process 

 was further improved by Messrs Dolfus, Meig, & Co., in France, and Mr 

 Lightfoot, in Lancashire, by printing murexide with an excess of nitrate 

 of lead, and subjecting the cloth so printed to the action of ammoniacal 

 fumes, or passing it through a solution of caustic soda mixed with sal 

 ammoniac. In order to render this substance more generally useful, it 

 remained to find a method for obtaining fast colours with it on mixed 

 fabrics, such as mousseline de laine ; and this has also been effected by 

 M. Schlumberger. The cloth is first prepared by uniting binoxide of tin 

 with the wool. This object is attained by using a salt known to calico- 

 printers as pink salt, the double chloride of ammonium and tin, and then 

 printing on the prepared fabric the following mixture : 



1 part of murexide. 



6 parts of nitrate of lead. 



2 parts of nitrate of soda. 



