452 MORBID PRODUCTS. 



An analysis of a calculus containing a considerable amount 

 of carbonate of magnesia is given in p. 458. 



"This salt is of frequent occurrence in calculi of the lower 

 animals. 



\Urostealith. We have already (see page 326) noticed Heller's 

 discovery of urostealith. 



The concretions that were discharged were round and had 

 not the appearance of being fragments of a larger calculus ; in 

 consequence of the locality of the pain it was presumed that 

 they were renal calculi. Altogether a little more than a 

 drachm of urostealith was collected. The concretions varied 

 from the size of a hempseed to that of half a small nut. Most 

 commonly they were of the size of a pea, and either consisted 

 of pure urostealith or had an outer coating of ammoniaco- 

 magnesian phosphate. 



Urostealith is most readily detected by the effects of heat 

 and combustion. A fragment placed on platinum foil and 

 heated remains for some time solid, then commences to fuse 

 without thoroughly melting, swells, and diffuses much vapour, 

 giving off an extremely peculiar and pungent odour, resembling 

 that of shell-lac and benzoin. The odour is so strong as to be 

 distinctly evolved by the smallest piece of urostealith. After 

 fusing and swelling up, it catches fire (if touched by the flame 

 of the lamp), and burns with a clear yellow flame. A volu- 

 minous coal is left which, when thoroughly burned, leaves a 

 very minute alkaline ash, consisting principally of lime. 



When boiled in water urostealith becomes soft but does not 

 dissolve. Warm alcohol dissolves it, but with difficulty; when 

 the alcohol is evaporated and the residue burned the fragrant 

 odour is developed. Ether dissolves it pretty freely; on evapo- 

 ration the urostealith is left in an amorphous form, and on con- 

 tinuing a gentle heat it assumes a well-marked violet tint. It 

 dissolves readily in a hot solution of caustic potash, forming a 

 brown soap; and on treating this solution with an acid the 

 urostealith again separates as amorphous fat. The carbonates 

 of potash and soda act similarly but more slowly. When heated 

 with nitric acid it yields a colourless solution, a slight quantity of 

 gas being developed : on treating the residue (after evaporation) 

 with ammonia or potash it becomes of a dark yellow colour. 1 ] 



1 Heller's Archiv fur physiologische und pathologische Chemie, vol. 2, pp. 1-12. 



