120 ANIMAL OXIDES WITH AZOTE NOT OILY. 



The subsequent experiments of Vauquelin* and Lassaigne,f 

 show only that these chemists conceived that there existed in pur- 

 purate of ammonia another substance, besides those pointed out 

 by Prout, but which they did not obtain or characterize by any- 

 positive results. 



Murexide was obtained by Wohler and Liebig in the following 

 manner : One part of uric acid was put into a porcelain capsule 

 and moistened with thirty-two times its weight of water. The 

 mixture was raised to the boiling point, and nitric acid of speci- 

 fic gravity 1*425 previously mixed with twice its weight of water 

 was added by small quantities at a time, waiting till the effer- 

 vescence was at an end before a new quantity was added. The 

 addition of nitric acid was stopped when only a trace of uric acid 

 remained. The liquid was raised to the boiling point, filtered 

 and evaporated by a gentle heat. During this evaporation a 

 slight effervescence was continually observed. The liquid when 

 concentrated to a certain point became coloured. The evapora- 

 tion was stopped when the liquid assumed the colour of an onion. 

 It was cooled down to 158, and then dilute caustic ammonia 

 was added. 



The success of the process depends upon the quantity of am- 

 monia, and on the temperature. The liquid should contain a 

 very slight excess of ammonia. It ought neither to be cold nor 

 hotter than 158 ; otherwise the compound is destroyed by the 

 free ammonia and another formed. The colour of the liquid is 

 so intense that it is opaque. We cannot therefore assist our- 

 selves in determining the requisite proportions by the reactions of 

 vegetable blues. The smell is the best means of determining if 

 the quantity of ammonia added be sufficient. 



Dr Gregory of Aberdeen has^ given the following process for 

 preparing murexide: Dissolve seven grains of alloxane (con- 

 taining its water of crystallization), and four of alloxantin in 240 

 grains of water by boiling, and add the hot solution to 80 minims 

 of a cold strong solution of carbonate of ammonia. Collect the 

 crystals after some hours, slightly wash them with cold water, and 

 dry them by pressure between folds of paper.J 



During and after the cooling are deposited the magnificent 

 crystals of murexide. They have a green colour and the metal- 



* Jour. de Phys. Ixxxviii. 258. f Ann. de Chim. et de Phys. xxii. 33<t 

 Ann. der Pharra. xxxiii. 334. 



