Ii8 Experiments on Plaiina. 



But if with this mode of operating we compare the quan- 

 tities of real acid, faid (in thofe excellent tables with which 

 Mr. Kirwan has enriched the fcience) to be contauied in ful- 

 phuric acid of diflerent fpecific gravities, each will fervc as a 

 proof of the validitv of the other ; and perhaps demonftrate, 

 that fulphuric acid, wilhout the intervealion of water, may 

 enjoy liquidity at the temperature and preflurc which aft 

 upon our globe. 



XIX. Experiments on Plaiina. By L. Proust. 



[Continued from p. 55.] 



XIII. Of the Crjj] alligation of Solutions of Platina, 



T. 



H E fmall yellow, red, and fand-like grains which ape 

 depofited at the. bottom of the united folutions, and which 

 fometimcs aiiume the oclaedral form, are generally taken for 

 muriate of platina. The quantity of thefe cryftals, which is 

 always verv fmall, does not increafe by concentration; which, 

 however, ought to be the cafe, if thefc cryftals were really 

 muriate of platina. No more of ihem appear in folutions. 

 from which they have been once fcparated ; and their fepa- 

 ration is even complete a long time before the moment when 

 the real muriate of platina begins to cryftallize. 



Thefe cryftals are a double fait, compofed of muriate of 

 platina and potafh, as will be fcen hereafter : they are formed 

 from the fmall quantity of potafli which, bv the inadvertency 

 of the workmen, remains in the neck of the retorts, when 

 preparing nitric acid, and from that aifo which is carried 

 over in the diftillation itfelf; for nitre is always found, after 

 the reftificaiion of anuafonis, at the botUnn of the retorts. 

 The greater part of thofe who have operated on platina 

 having in general employed the acids fold in the Ihops, we 

 need not be furprifed that they fhould have found cryftalline 

 depofits of tlie kmd here alluded to, and th^t none of them are 

 ever feen in folutions made on purpole with acids well purified. 



If fome of thefe cryftals be heated in a glafs tube clofed at 

 one end, their nature may be foon diflinguifhed : becaufe the 

 muriatic acid, charged with the oxygen of the metal, is vo- 

 latilized in gas; while the platina, reduced to the metallic 

 Hate, and mixed with the muriate of potafh, remains at the 

 bottom of the lube. 



IL.e\vis, in my opinion, is the only perfon who has accu- 

 rdt<.ly obfcrved the cryilallization of platina. The folution 



was 



