290 AJS T NUAL OF SCIENTIFIC DISCOVERY. 



Some time since, however, Dr. Sacc turned his attention to the subject, 

 and led by the fact above mentioned, that a solution of alloxan stained 

 the skin, came to the conclusion, that, by impregnating a piece of woollen 

 cloth with that substance, he might be able to produce the murexide di- 

 rectly in the tissue. He tried the experiment, and succeeded in dyeing a 

 piece of cloth of an amaranthus tint, far more beautiful than that pro- 

 duced by cochineal. He communicated the results of his first experi- 

 ments, still incomplete, to M. Albert Schlumberger, who has succeeded, 

 by modifying and completing the experiments of Dr. Sacc, in rendering 

 the process, merely indicated by the latter, perfectly practicable. 



His process is simple enough. He prepares a solution of alloxan, 

 formed of 30 grms. of alloxan to each litre of water, and soaks the tissue 

 to be dyed in it, the excess of liquid being then squeezed out in the or- 

 dinary way, or by pressure between rollers. The cloth is then dried at a 

 gentle temperature, and after an ageing of twenty-four hours the color is 

 brought out by passing the cloth over a roller heated to 212 F. For this 

 purpose the drying machines composed of several drums would answer 

 perfectly, the cloth being successively passed over each, the greatest care 

 being taken to avoid folds ; woollen yarn and wool should be put in a 

 stove heated by steam. According as the heat is communicated to the 

 cloth, a magnificent purple tint, far more beautiful than any thing hitherto 

 produced by the ammoniacal preparation of cochineal, or by red dye- 

 woods, makes its appearance as if by magic. The intensity varies accord- 

 ing to the strength of the solution of alloxan which has been employed. 

 It is only necessary to wash the cloth in cold water to give to the shade 

 its full brilliancy. 



M. Sacc found that the finest and most vivid shades could only be com- 

 municated to the tissues mordanted with salts of peroxide of tin, and M. 

 Schlumberger has confirmed this observation. Cloth not mordanted did 

 not give very satisfactory results, even after a prolonged exposure to warm 

 and damp air. He obtained the most satisfactory results by soaking the 

 cloth in a solution composed of equal parts of per chloride of tin and oxalic 

 acid, of a specific gravity of 1.006. In this solution, at a temperature of 

 about 100 F., the cloth is to be allowed to remain for an hour, then 

 rinsed and dried, and is then fit to be treated with alloxan. If stronger 

 solutions of the mordant be employed, there is a considerable loss of color- 

 ing material and a deterioration of the shade. This may be attributed to 

 the presence of too great an excess of stannic acid, which from its opacity 

 may mask the murexide, or by its acid reaction may decompose it. rf This 

 is especially the case if chloride of tin be employed instead of stannate of 

 soda. Experience has shown that fabrics freshly mordanted give better re- 

 sults that those which have been mordanted for some time ; the deprecia- 

 tion in purity and brilliancy of tint in the latter may even amount to 20 

 or 30 per cent. 



Murexide, as we have already remarked, being produced by the action 

 of heat and ammonia, it occurred to M. Daniel Dollfus, and the other 



