104 ANIMAL OXIDES WITH AZOTE NOT OILY. 



mined by Dr Marcet. In the year 1816, a similar calculus was 

 extracted from a patient by Langenbeck, and given to Stromeyer, 

 who determined it to be the same as the xanthic oxide of Marcet. 

 A considerable portion of this calculus is still in Langenbeck's 

 collection. It weighs eleven grammes, or almost 170 grains. 

 It is much larger than the one described by Marcet. It has been 

 lately examined and analyzed by Wohler and Liebig, * 



The surface of the calculus was partly light brown, smooth, and 

 shining, partly earthy and whitish. The fracture had a brownish 

 flesh-colour. It was composed of concentric layers, separable 

 from each other, and had a nucleus composed of the same mat- 

 ter with the rest of the calculus. It had the same degree of hard- 

 ness as the uric acid calculi. When rubbed or scraped, it as- 

 sumed a waxy lustre. 



As it might be supposed to contain more or fewer of the con- 

 stituents of urine, Wohler and Liebig purified the xanthic oxide, or 

 uric oxide, as they have called it, in the following way : The cal- 

 culus was pulverized and dissolved in caustic potash. The solu- 

 tion had a dark brownish yellow colour, with a shade of green, 

 not unlike the colour of bile. Through this solution pure car- 

 bonic acid gas was passed till the potash was converted into bi- 

 carbonate. The uric oxide precipitated in the form of a white 

 powder. When this powder was washed and dried, it assumed 

 the form of masses of a light yellow, which, when rubbed, acquir- 

 ed a waxy lustre. It contained no trace of potash, differing in 

 this respect from uric acid. For when an alkaline solution of 

 this last is saturated with carbonic acid gas, the precipitate is not 

 pure uric acid, but urate of potash. 



Uric oxide is soluble in sulphuric acid, and the solution has a 

 yellow colour. The oxide is not precipitated by water. In this 

 respect also it differs from uric acid. It is insoluble in muriatic 

 and oxalic acid ; a circumstance which distinguishes it from cystic 

 oxide. 



When subjected to destructive distillation it so far resembles 

 uric acid, that a great deal of hydrocyanic acid is evolved. But 

 the empyreuma has a different smell, similar to that of distilled 

 horn. There is given out also a sublimate of carbonate of am- 

 monia, but no urea. 



When heated with oxide of copper the azotic was to the car- 



* Ami. der Pharm. xxvi. 340, 



