IfEW SPECIES OF URINIHY CALCULUS. £25 



but I could discern nothing \vbich enabled me to judge of 



the primitive form of the crystal. On the surface of the 



calculus belonging to Gov's Hospital, e^ome minute crys- perhaps cubit 



tals may be discerned of a different shape, being nearly ^^«n pure.- - 



cubic. And it is possible, that the hexagonal crystals may 



owe their figure to a small portion of alkali remaining in 



combination. 



From the ready disposition of this substance to unite Combined 

 with both acids and alkalis, it would appear to be an oxide ; ^^^ oxigen, 

 and that it does, in fact, contain oxigen, is proved by the 

 formation of carbonic acid in distillation. The quantity of ".J^"®'*" 

 oxigen present in the calculus is not, however sufficient to 

 give it acid properties, for it has no effect on paper coloured 

 with litmus. 



I am therefore inclined to consider it as an oxide ; and Cystic oxid«. 

 since both the calculi, that have yet been observed, have • t 



been taken from the bladder, it may be convenient to give '"^ ' 



it the name of cj/stic oxide, which will serve to distinguish 

 it from other calculi ; and as this is unlike any other term 

 at present employed in chemistry, it is to be hoped, that it 

 will not be thought to require any alteration. 



Since the period of my first essay on gouty and urinary Mulberry cal- 

 concretions, the general results contained in it have been ^" "^* 

 confirmed by others, and 1 believe are incontrovertible. 

 But I am under the necessity of acknowledging a mistake ia ;. 

 the analysis of the mulberry calculus, though not of much 

 importance. An acid is mentioned to have arisen by sub- 

 limation, and it was supposed to originate from a partial ^,. _ ^ 

 decomposition of the oxalic acid. But since pure oxalate 

 of Time yields no such sublimate, it most probably arose 

 from a mixture of the small quantity of uric acid in the cal- 

 culus then under examination. 



In the analysis of the triple phosphate of magnesia, there Mistake in tha 

 is another mistake of more consequence. In mv selection analysi-. of tbe 

 trom numerous experiments tor ascertaming the presence of phai?? cf raag. 

 phosphoric acid, I gave the preference to one in which ni- ^^'"'* 

 trate of mercury was employed, on account of the facility of 

 extracting the acid from the phosphate of mercury by heat 

 alone. But since the whole of the phosphoric acid- is not i 



precipitated by nitrate of mercury, sulphate of magnesia 



YoL.XXVill.-MARCH, 1811. q will 



