120 On Gravelly and Calcuhns Concretions. 



much as possible assisted by experiment, I shall, for the 

 encouragement of the young practitioner, exhibit a few on 

 this very soluble species the more willingly, as he has no 

 assistance to expect from his professional books; these sub- 

 jects being only treated of in Philosophical Transactions, 

 Memoirs of the National Institute, and a few other foreign 

 chemical publications, if we except Whyte's Treatise on 

 Lime Water, to which we would willingly refer him. 



Experiment XVIII, 



An entire calculus, of a reddish, gritty appearance, exter- 

 nally, proved to consist of ammoniaco-magncoian phos- 

 phate, weighinj fortv-six grains one quarter, was suspended, 

 for forty-eight hours, in a mixture con»istiny;of four ounces 

 of distilled water and ten drops of weak marine acid. After 

 being taken out, and dried, it was found to have lost six 

 grains three quarters. The mixture was whitish, lost it^ 

 acid taste, and precipitated, on the addition of a few drops 

 of fixed alkali, the ammoniaco-magnesian phosphate, under 

 that beautiful crystalline form so accurately described by 

 Dr. Wollaston. 



We may readily conceive how much more the loss wourd 

 have amounted to in this case, in the short space of forty- 

 eight hours, if the menstruum had been frequently repeated 

 under the regular influence of human temperature. 



Experiment XIX. 



A fragment of the same species with the above, weighing 

 twelve grains, was immersed, for forty-eight hours, in three 

 ounces of distilled water, without addition : temperature 

 from 60 to near 100 degrees. After being taken put, and 

 dried, it was found to have lost one grain three quarters, 

 became so friable as to crumble, and the solution to preci- 

 pitate with a few drops of pure ammonia. 'Jhis species of 

 calculus, therefore, is soluble in water, at temperatures even 

 inferior to that of the human. It is unnecessary I should 

 enter into a further detail of experiments made upon calculi 

 of the mixed kind, having the uric acid, phosphate of am- 

 monia, and sometimes, though rarely, phosphate of lime, 



intermixed 



