256 PHILOSOPHICAL TRANSACTIONS. [ANNO 1798. 



perceive, from a few experiments, that urinary concretions consisted of animal 

 matter and the earth of bone, before the composition of this earth was demonstra- 

 ted by Gahn. 



In this historical sketch it should be noticed, that alkaline substances, though 

 used by the Greek physicians, and afterwards by the alchemical physicians, appear 

 to have been laid aside by the regular practitioners, for a century or 2 preceding 

 their revival, by the famous Mrs. Stephens, in 1720. Her prescription brought 

 into vogue the theory of these medicines operating by their causticity. The suc- 

 cessful use, by Mr. Colborne, of pot-ash saturated with carbonic acid, according 

 to the discovery of Bewlev and Bergman, and the still further improvement in 

 practice, from the use of soda, as well as pot-ash, super-saturated with carbonic 

 acid, by the discovery of a peculiar method by Mr. Schweppe, have completely re- 

 futed the theory of the agency of alkalies on the principle of causticity. It appears, 

 from the preceding brief history, as well as from the confession of the latest and 

 best writers, that the experiments hitherto made, rather " afford indications of 

 what remains to be done, than furnish demonstrations of the nature of animal con- 

 cretions." It is also too obvious to need explanation, that more efficacious and 

 innocent practice, in diseases of these concretions, can only be discovered by a 

 further investigation of their properties. It is with this view, as well as for the 

 sake of chemical philosophy, that I think it my duty to submit to the r. s. some 

 of the observations I have made, in the course of inquiry on this subject. 



The observations which I shall now offer, are principally on a substance, which 

 my experiments inform me is very generally a constituent of both urinary and ar- 

 thritic concretions. It is a substance obtained by dissolving it out of these concre- 

 tions, by lye of caustic fixed alkali, and precipitating it from the solution by acids. 

 In this way, Scheele separated this matter; but he did not consider its importance, 

 nor of course at all investigate its properties. He does not even seem to have been 

 aware that it was a distinct constituent part of the urinary concretion ; for when he 

 relates the experiment of precipitating matter from the nitric solution of calculus 

 by metallic salts, no distinction is made between the precipitations in this experi- 

 ment, and that in the former; yet we can now show, that in the one case the pre- 

 cipitate is a peculiar animal oxide, and in the other they are metallic phosphates. 

 As Scheele obtained an acid sublimate, it has been imagined by some writers, that 

 the precipitate by any acid, even by the carbonic, from the alkaline menstruum, 

 was an acid; the same as that obtained by sublimation, and which, in the new 

 system of chemistry, has been denominated lithic acid. The following experiments 

 show that these substances are different species of matter. 



2. Exper. 250 grs. of a white, smooth, laminated, urinary calculus, and the 

 same quantity of a nut-brown one, with an uneven surface, both of which were 

 of a roundish figure, were pulverized together*. 300 grs. of these pulverized 



* The object of these experiments being principally to investigate the properties of one of the con- 

 stituent parts of urinary concretions, which part was previously determined by the test of nitric acid, to 



