214 PHILOSOPHICAL TRANSACTIONS. ["ANNO 1797. 



time, has received the name of lithic acid. In the following paper I purpose giving 

 an account of the analysis of gouty concretions, and of 4 new urinary calculi. 



The gouty matter, from its appearance, was originally considered as clmik , but 

 from being found in an animal not known to contain or secrete calcareous earth 

 uncombined with phosphoric acid, it has since been supposed to resemble earth of 

 bones. Dr. Cullen has even asserted, that it is f very entirely' soluble in acids. 

 The assertion however, is by no means generally true, and I think he must pro- 

 bably have used the nitrous acid, for I find no other that will dissolve it. Another 

 opinion, and I believe at this time the most prevalent, is, that it consists of lithic 

 acid, or matter of the calculus described by Scheele. But this idea is not I believe 

 founded on any direct experiments, nor is it, to my knowledge, more ably sup- 

 ported than by Mr. Forbes, who defends it solely by pathological arguments from 

 the history of the disease. Had he undertaken an examination of the substance 

 itself, he would have found that, instead of a mere concrete acid, the gouty matter 

 is a neutral compound, consisting of lithic acid and mineral alkali ; as the following 

 experiments will prove. 



(1) If a small quantity of diluted vitriolic acid be poured on the chalk-stone, 

 part of the alkali is extracted, and crystals of Glauber's salt may be obtained from 

 the solution. Common salt may still more easily be procured by marine acid. The 

 addition of more acid will extract the whole of the alkali, leaving a large propor- 

 tion of the chalk-stone undissolved ; which exhibits the following characteristic 

 properties of lithic matter, (a) By distillation it yields a little volatile alkali, Prus- 

 sic acid, and an acid sublimate, having the same crystalline form as the sublimate 

 observed by Scheele. (b) Dissolved in a small quantity of diluted nitrous acid it 

 tinges the skin with a rose colour, and when evaporated leaves a rose-coloured de- 

 liquescent residuum, (c) It dissolves readily in caustic vegetable alkali, and may 

 be precipitated from it by any acid, and also by mild volatile alkali ; first as a jelly, 

 and then breaking down into a white powder. 



(2) In distillation of the chalk-stone the lithic acid is decomposed, and yields 

 the usual products of animal substances, viz. a fetid alkaline liquor, volatile alkali, 

 and a heavy fetid oil, leaving a spongy coal ; which when burnt in open air fuses 

 into a white salt, that does not deliquesce, but dissolves entirely in water, is alka- 

 line and when saturated with nitrous acid gives rhomboidal crystals. These cha- 

 racteristic properties prove it to be mineral alkali. 



(3) Caustic vegetable alkali poured on the chalk-stone, and warmed, dissolves 

 the whole, without emitting any smell of volatile alkali. From which it appears, 

 that the volatile alkali obtained by distillation is a product arising from a new arrange- 

 ment of elements, not so combined in the substance itself. 



(4) Water aided by a boiling heat dissolves a very small proportion of the gouty 

 concretion, and retains it when cold. The lithic acid thus dissolved in combination 

 with the alkali, is rather more than would be dissolved alone ; so that by addition 

 of marine acid it may be separated. While the solution continues warm no preci- 



