URIC OXIDE. G3 



solution by a stream of carbonic acid. It forms a white pre- 

 cipitate, which, when di'ied, constitutes a pale yellow hard mass. 

 It is represented by the formula' Cj^ H^ N^ O^. It differs 

 fi'om ui'ic acid in containing two atoms less oxygen, hence 

 the name of uric oxide. It dissolves in the alkalies, in small 

 quantity in hot water, hydrochloric and oxalic acids, it is in- 

 soluble in alcohol and ether, and produces no effect on test 

 paper. It dissolves also in concentrated sulphuric acid with a 

 yellow coloui*, and no precipitate is caused by the addition of 

 water to the solution. It is soluble in hot nitric acid ivithout ef- 

 fervescence,'^ and more slowly than uric acid. On carefully eva- 

 porating this solution, a lemon-yellow residue is left, which is 

 not reddened by the vapour of ammonia, but which is dissolved 

 with a reddish yellow colour by caustic potash, and leaves, on 

 evapoi'ation, a red residue. IMuriate of ammonia throws doAvn 

 a yellow precipitate from the potash solution. Uric oxide 

 differs from uric acid in being insoluble in a dilute solution of 

 carbonate of potash ; by this property these two substances 

 may be separated from one another when they occur together. 



Dulk conceives that he has effected the metamorphosis of 

 uric oxide into uric acid. The j^ellow nitric-acid solution of 

 ui'ic oxide was evaporated on a watchglass to a thick consist- 

 ence. After a few days, small, hard, and transparent crystals 

 appeared. A little of the portion which remained fluid, when 

 heated on a platinum spatula over the flame of the spirit-lamp, 

 assumed a blood-red tint, and in a few days the fluid which 

 remained in the watchglass, exposed to the atmosphere, under- 

 went a similar change of colour. He considers the small crystals 

 which were formed to consist of alloxantin ; and, in support of 

 his \\Q\y, he alleges the following facts. Cold water poured 

 over them assumes a red tint, but does not dissolve them ; they 

 are, however, perfectly soluble in boiling water, and, on the 

 addition of ammonia to a hot concentrated solution, a reddish 

 coloui' manifests itself, which disappears on cooling. On con- 

 centrating a portion of the solution to a few di'ops, mixing it 

 with nitric acid, and then adding ammonia, a greenish salt 

 separated itself. 



Lehmann instituted a series of experiments with the view of 



' See Appendix I, Note 21. 



^ Dulk states that, in his case, the uric oxide did slightly effervesce. 



