40 



bladder than 

 those of the 

 kidney. 



One supposed 

 to consist of 

 yrate of am- 

 monia digested 

 in water. 



Solution eva- 

 porated. 



Another di- 

 gested in alco- 

 hol. 



Solution eva- 

 jporatecj. 



ON THE STRUCTURE OF CALCULI. 



tempting to obtain their pure uric acid, than in the kidney 

 calculi, which led me to suppose, that they contained ureal 

 and that the presence of this substance, with some of the 

 salts of urine, and with small portions of the ammoniaco- 

 magnesian phosphate, was the cause of the occasional evo- 

 lution of ammonia when treated with the fixed alkalis, and 

 of their easy solubility in those substances. 



To determine this point, a small calculus, weighing 

 twenty-five grains, and of the species commonly supposed to 

 consist of urate of ammonia*, was digested for two hours 

 with water in a very moderate heat. The water which had 

 assumed a pale yellow colour was filtered off, and fresh 

 water added to the residuum three successive times, when 

 it appeared, that every thing soluble in that fluid was sepa* 

 rated. The insoluble part of the calculus, being now care^ 

 fully dried and weighed, was found to have lost 5*5 grains. 



The aqueous solution was evaporated by a gentle heat, 

 nearly to dryness, and a substance was obtained having all 

 the properties of urea, in combination with a small portion 

 of muriate of ammonia, and of the ammoniaco-magnesian 

 phosphate. 



Sixty grains of another calculus of a considerable size, 

 supposed from a superficial analysis, to consist of nearly pure 

 urate of ammonia, were digested at a low temperature in 

 one ounce of alcohol. In an hour the alcohol was decanted 

 off, and fresh portions were added successively, as long as 

 it appeared to act upon the calculus, which, after having 

 been carefully dried in a temperature below 212°, weighed 

 54«8 grains, so that 5*2 grains had been taken up by the al* 

 cohol. 



On evaporating the alcoholic solutions, a substance was 

 obtained having all the properties of urea, with a small por-r 

 tion of saline matter, probably muriate of ammonia, as by 

 the addition of potash a slight ammoniacal odour was per- 

 ceptible; its quantity however was too minute for accurate 

 examination. 



• Fourcroy observes, that urate of ammonia is easily detected by it* 

 tapid solubility in the fixed alkalis, and the odour of ammonia, which is 

 perceived during its soluticn.-»Vide Thomson's Svst. of Chem. vol. v, 



* 65t - Th, 



