VOL. LXXXVII.] PHILOSOPHICAL TRANSACTIONS. 21 5 



pitate is formed ; but as it cools, the lithic acid crystallizes on the sides of the ves- 

 sel, in the same manner as the crystals called red sand do, when an acid is added to 

 recent urine. The gouty concrete may be easily formed by uniting the ingredients 

 of which I have found it to consist. 



(5) If a fragment of lithic acid be triturated with some mineral alkali and a 

 little warm water, they unite, and after the superfluous alkali has been washed out, 

 the remainder has every chemical property of gouty matter. The acid will not 

 sublime from it, but is decomposed (2) by heat : the alkali may be extracted 

 by the vitriolic or marine (l), or indeed by most acids. The compound re- 

 quires a large quantity of water for its solution (4), and while warm the solution 

 yields no precipitate by the addition of an acid ; but on its cooling the lithic crys- 

 tals form, as in the preceding experiment. In each case the crystals are too small 

 for accurate examination, but I have observed, that by mixing a few drops of 

 caustic vegetable alkali to the solution previous to the decomposition, they may be 

 rendered somewhat larger. At the first precipitation, the crystals from gouty mat- 

 ter were not similar to those of lithic acid ; but by redissolving the precipitate in 

 water with the addition of a little caustic vegetable alkali, and decomposing the 

 solution as before, while hot, the crystals obtained were perfectly similar to those 

 of lithic acid procured by the same means. 



Such then are the essential ingredients of the gouty concretion. But there 

 might probably be discovered, by an examination of larger masses than I possess, 

 some portion of common animal fibre or fluids intermixed ; but whatever particles 

 of heterogeneous matter may be detected, they are in far too small proportion to 

 invalidate the general result, that c gouty matter is lithiated soda.' The knowledge 

 of this compound may lead to a further trial of the alkalies which have been ob- 

 served by Dr. Cullen to be apparently efficacious in preventing the returns of this 

 disease (First Lines, dlviii) ; and may induce us, when correcting the acidity to 

 which gouty persons are frequently subject, to employ the fixed alkalies, which are 

 either of them capable of dissolving gouty matter, in preference to the earths, 

 termed absorbent, which can have no such beneficial effect. 



Fusible calculus. — My next subject of inquiry has been a species of calculus, that 

 was first ascertained to differ from that of Scheele by Mr. Tennant ; who found 

 that when urged by the heat of a blow-pipe, instead of being nearly consumed, it 

 left a large proportion, fused into an opaque white glass, which he conjectured to 

 be phosphorated lime united with other phosphoric salts of the urine, but never 

 attempted a more minute analysis. Stones of this kind are always whiter than 

 those described by Scheele, and some specimens are perfectly white. The greater 

 part of them have an appearance of sparkling crystals, which are most discernible 

 where 2 crusts of a laminated stone have been separated from each other. I lately 

 had an opportunity of procuring these crystals alone, voided in the form of a white 

 sand, and thence of determining the nature of the compound stone, in which these 

 are cemented by other ingredients. The crystals consist of phosphoric acid, mag- 



