MUREXIDE 



375 



hot solution is added to one-sixth of an ounce by measure of a saturated or nearly 

 saturated solution of carbonate of ammonia, the latter being cold. This mixture has 

 exactly the proper temperature for the formation of murexide ; and it does not, 

 owing to its small bulk, remain too long hot. It instantly becomes intensely purple, 

 while carbonic acid is expelled ; and as soon as it begins to cool the beautiful green 

 and metallic-looking crystals of murexide begin to appear. As soon as the liquid 

 is cold, these may be collected, washed with a little cold water, and dried on filtering- 

 paper.' 



The analyses of murexide are rather discordant, the carbon in all of them being in 

 excess. This arises from the very large amount of nitrogen present, a certain portion 

 becoming acidified passes into the potash apparatus, causing an undue increase in its 

 weight. The following are the principal analyses : 



There appears no doubt whatever that the formula C 16 N 6 H 8 12 represents its true 

 composition. Murexide is formed when uramile, murexane, or dialuramide, as it is 

 sometimes called, is boiled with peroxide of mercury. Dr. Gregory regarded murexane 

 as a separate substance, and as identical with purpuric acid ; he also considered 

 C 8 N 2 H 4 5 as its probable formula. This appears from more recent researches to be 

 incorrect, as murexane is doubtless the same substance as uramile, while purpuric acid, 

 which is bibasic, is represented by the formula C 16 H 5 N 5 12 . The formulae above given 

 for murexide and uramile renders the reaction of peroxide of mercury with the latter 

 easily intelligible ; it is, in fact, a very simple case of oxidation, thus : 



2C S N 3 H 5 8 + 20 = C 16 N 8 H 8 0' Z + 2HO (C 8 N 6 H'O + O = C 8 N 8 H 8 O 8 + H 2 O). 



Uramile. 



Murexide. 



The limits of this work preclude any further notice of the scientific relations of 

 murexide, but it is necessary that we should consider it in its character as a dye-stuff. 

 It has been found that murexide forms a series of beautiful compounds with certain 

 metallic oxides, more especially lead and mercury, and these compounds have been 

 employed to a very large extent in the dyeing, and more especially printing, of cotton 

 goods. It is plain that if uric acid were only obtainable from the urine of serpents or 

 the sediments from the tirine of mammalia, it could never be made use of in the arts. 

 It happens, however, that the solid urine of birds contains it in large quantity, and 

 since we have become acquainted with the vast deposits of guano existing in various 

 parts of the globe, the manufacture of murexido has been carried out on a scale which 

 would, a few years ago, have appeared impossible. We must, in order to be clear, 

 divide the process into two parts : one being the preparation of uric acid from guano, 

 the other the conversion of the acid into murexide. 



Preparation of Uric Acid from Guano. In order to get rid, as much as possible, of 

 thp impurities contained in the guano, it is in the first place to be treated with muriatic 

 acid, which, will remove carbonate and oxalate of ammonia, carbonate and phosphate of 

 lime, and ammonio-magnesian phosphate. The uric acid will also be liberated from 

 the substances with which it may be in combination. The operation may be per- 

 formed in a leaden vessel, heated with a leaden coil, through which steam passes. It 

 is essential to success that tho guano be added slowly, otherwise the violent effer- 

 vescence, which is caused by the decomposition of the carbonates by the acid, would 

 cause the liqxiid to escape from the vessel. The mixture of guano and muriatic acid 

 is then to be heated for an hour, after which it may be run off into tubs to be washed 

 with water by decantation. The first washings contain a large quantity of ammonia 

 in the state of sal-ammoniac; it should be worked up in some way, in order to prevent 

 the loss of so valuable a salt. As soon as the residue of the guano is sufficiently 

 washed it may be transferred to cloth filters and allowed to drain. The residue from 

 the action of muriatic acid upon 200 Ibs. of guano can now be treated by Braun's process 

 for the extraction of the uric acid, It is to be placed in a copper boiler of sufficient 

 capacity, and boiled for an hour with 8 Ibs. of caustic soda and 120 gallons of water. 

 It must be constantly stirred. Two or three pounds of quicklime are now to be slaked, 

 enough water is then to be added to make the whole into a thin paste, which is to be 

 poured into tho mixture of caustic soda and guano residue. After a quarter of an 



