ggg KEW SPECIES OF URINARY CALCULUS. 



will not be formed on the addition of sulphuric acid, and 

 the magnesia cannot be obtained separate by the same pro- 

 cess. 



led to another. It may have been in consequence of this oversiirlit, that a 

 mistake on that subject has occurred in the succeeding vo- 

 ^ lu me of the Transactions. 



Calculus of a A calculus is there described, which had been taken by 



dog suppo^d ^j.^ Thomas from the bladder of a doi- ; and a series of ex- 

 to «ontain lime ^ ... 



periments are related, from which it was inferred to consist 



of superphosphate of lime, and phosphate of ammonia. 

 But from the appearance of this calculus (which was exhi- 

 bited to the society at the time when the paper was read) I 

 was much inclined to think, that the nature of it was mis- 

 taken ; and upon full consideration of the experiments, 

 they did not appear to me conclusive. 

 \vas afterward ^ therefore, obtained a portion of the calculus, and, by 



proved to be a ^jje following process, the earth contained in it was proved to 



compound of . ^ , i. i ii i» 



magnesia. consist almost wholly oi magnesia. 



It was dissolved, with the exception of a very small re- 

 siduum, by distilled vinegar. 



The whole of the phosphoric acid was then precipitated 

 by acetate of lead added to excess. 



The liquor was then poured off, and sulphuric acid was 

 added, which precipitated the excess of lead, and at the 

 same time formed sulphate of magnesia in solution. 



By evaporation to dryness, the acetic acid was removed, 

 and by subsequent increase of heat, the sulphate of am- 

 monia, and excess of sulphuric acid were expelled. 



The residuum being then dissolved in water, and the 



iiquor suffered to crystallize by spontaneous evaporation, 



.there remained a quantity of sulphate of magnesia, that 



weighed rather more than the quantity of calculus taken 



for the experiment. 



Superphos- ^^ ^^^^ evident, therefore, that in this instance the cal- 



jjhate of lime cuius examined did not consist of superphosphate of lime ; 



perhaps never ^^^^ there 18 some reason to doubt, whether a compound, 



exists ma ^ i i i • <» r • 



cAlculus. *j.^^***^ ^^ *^ very soluble m water, ever lorms a part of, urinary 



-concretions. 

 P event'on oH'- Although the treatment •f diseases is not in general a 

 calcuiouscom- fii subject to occupy the lime of this society, there is never- 

 pbiats. theies* 



