TENDENCY TO CALCULOUS DISEASES. 79 



Of phosphate of lime, and the mixed phosphates. 



During my analysis of the Norwich collection, I was accidentally led to 

 suspect that carbonate of lime, though very unusual in urinary calculi in a 

 separate and distinct form, was not an unfrequent concomitant of phosphate 

 of lime. A particular examination of the collection, with a view to this special 

 point, convinced me that such was the case. The existence of carbonate of 

 lime was evinced by effervescence, on submitting a portion of the powdered 

 calculus, to the action of dilute muriatic acid, in a small tube, after boiling it 

 in distilled water, to extricate the atmospheric air involved in it. The gas 

 evolved, was readily absorbed by pure potash over water ; while pure ammonia 

 deposited the phosphate of lime, leaving a portion of fluid, from which lime 

 was thrown down by oxalate of ammonia. — The same circumstance, likewise, 

 happened, when the muriatic solution was evaporated to dryness, and the dried 

 portion submitted to distilled water ; the muriate of lime, formed by the solu- 

 tion of the carbonate being dissolved, and the lime precipitated in the form of 

 oxalate, by oxalate of ammonia. Carbonate of lime, I have likewise seen in the 

 mixed phosphates, and so extensively, as to induce me to think it probable, that 

 phosphate of lime is seldom or never found in urinaiy concretions, either sepa- 

 rately, or in combination with the triple phosphate, uncombined with carbo- 

 nate. This circumstance seems to be the less unlikely, when it is considered, 

 that carbonic acid gas has been found to exist in a pure state in urine, and 

 separable by the mere aid of diminished atmospheric pressure. Tliis being the 

 case, it may fairly be expected to unite with some portion of lime during the 

 evolution of the latter, instead of suffering the whole of it to be employed in 

 forming oxalate, or phosphate of lime. 



I am happy in having had the kind assistance of Dr. Prout, and of Mr. Fa- 

 raday of the Royal Institution, in ascertaining the existence of carbonate of 

 lime, in some of the specimens of calculi in which that substance is not usually 

 looked for. To Dr. Prout the circumstance was not unexpected ; for he has 

 long considered the existence of carbonate, with phosphate of lime in human 

 concretions, exceedingly likely, though he had not put his ideas to the test of 

 experiment. — An important confirmation of these observations I have likewise 

 met with, in a paper by the distinguished Spanish chemist Proust, who states. 



