402 PUErLE DYEING, ANCIENT AND MODERN. 



May it not be mctamorpliosed into some other substance Avhicb, like tbe alloxan, 

 is capable of dyeing the feathers ? These questions are only suggested, and 

 we are not as yet able to supply the answers ; but this hypothesis, if adopted 

 with regard to birds, must also be extended to reptiles, insects, &c. 



The murexid is now a favorite dyeing material, strongly competiitg even with 

 cochineal. Germany, as usual, was the last to adopt it. In a new and little 

 known process mistakes are quite natural. When this new dyestuff first made 

 its appearance as an article of trade, under the names of purple carmine, purple 

 murcxide, or paste murexide, it was in the form of a dirty-brown pulp. Though 

 it sold as high as 84 SO to $6 the pound, it was a very inferior quality, 

 and in many cases contained not more than from four to five per cent, of the 

 murexid. Of course, this inferiority arose from imperfect preparation. 



To extract uretric acid from guano, the latter must be moistened with diluted 

 acid of salt, and warmed. Tlie calcareous salts and everythiiig soluble in water 

 . or acids is removed, while the uretric acid, Avith a not inconsiderable quantity of 

 sand and other adulterations, remains. The well-washed residue is then put, 

 in small quantities, into acid of saltpetre of 1.45 specific gravity, and the vessel 

 must be kept cold. Only when the fermentation subsides should more uretric 

 acid be added. .By this procedure alloxan and alloxantine are obtained. But it 

 must not be forgotten, that, as it is impossible to hit upon the exactly correct 

 quantity of the acid of saltpetre, we should always have a surplus of the acid 

 at hand. It must be remembered, too, that very noxious fumes escape during 

 the evaporation of the solution. The above-mentioned chemical products of 

 uric acid suffer a further decomposition, and form combinations destitute of 

 murexid. To avoid this, it is necessary that to the solution of uric acid and 

 acid of saltpetre there should, during the evaporation, be an addition of ammo- 

 nseum. Murexid may be formed without that addition, but always at the ex- 

 pense of the alloxan and alloxantine ; for if the ammonseum be absent during the 

 evaporation, the alloxan and alloxantine are required to supply its place in tho 

 chemical production of murexid during the evaporation ; and, moreover, the 

 decomposition just spoken of continues, and we run the risk of having the 

 murexid destroyed as fast as formed. 



The murexid must not be suffered to crystallize ; the solution is to be evapo- 

 rated only to the consistency of a pulp. In the whole process there should be 

 the utmost care observed that only the purest and best murexid be produced. 

 The high price of the pure article Avould be more than compensated by its 

 greater efBcacy in dyeing. All textile fabrics, silk, Avool, cotton, and flax, 

 may be dyed Avith murexid, Avhich is also used in cotton printing. Truly splen- 

 did colors are obtained by using the oxmuriate of mercury as the adhesive 

 medium. We are obliged, hoAvever, to confess Avith regret that the murexid red 

 cannot compare Avith the ancient purple as to durability. Samples on Avhich we 

 experimented Avith the usual re-agents lost their colors, hoAvever beautiful. "We 

 do not speak of such re-agents as the corroding alkalies and potent mineral acids 

 Avhich Avould affect, and in our experiments did affect, black no less than murexid 

 red. But this latter faded inider the application of cA'cn Aveak A-egetablc acids, 

 such as vinegar, lemon-juice, &c., and even perspiration left visible traces upon 

 the delicate tincture, llere, no doubt, are considerable defects ; but it is to be 

 remembered that the Avholc art of dyeing Avith murexid is as yet in its infancy. 

 Even the ancient purple Avas not indestructible, and in the present day the 

 public demand is not for indestructibility, but for cheapness. If the color please 

 the eye and the price per yard be Ioav, little is thought about the durability of 

 the article. Time and the progress of chemical science Avill doubtless remedy 

 the defects spoken of, since there can be no question but that this color is sus- 

 ceptible of great improvement. If the murexid be jirecipitated from its solu- 

 tions by metallic salts, as, for instance, oxymuriate of mercury, or salts of lead 

 or zinc, very beautiful lac colors arc obtamed, which can be used for the paint- 



