Mr, R. Phillips's Experiments on Platina. 95 



Supposing, therefore, the black precipitate to be a hydrate 

 of platina, it would appear by my experiments to be a com- 

 pound of about four atoms of the metal and one atom of water. 

 Now the existence of a hydrate so constituted is not only of it- 

 self extremely improbable, but is rendered still more unlikely 

 by the supposition that a metal without previous oxidizement 

 should form a hydrate at all ; for it is quite as contrary to ex- 

 perience that a metal and water should combine, as that a metal 

 and an acid should unite, without the intervention of oxygen. 



I am therefore disposed to consider the 1*41 per cent, of 

 water which remains with the black powder, after being heated 

 to 212°, as in a state of mixture, and not of combination. There 

 are other circumstances which strengthen this conclusion : 

 If the black powder be strongly pressed or rubbed in a glass 

 mortar, the metallic appearance of platina is as perfect before 

 as after the application of a red heat; and I conceive this could 

 scarcely occur if it were chemically combined with water. 

 That the platina is in the metallic state in the black powder, 

 is proved by its total insolubility in nitric or muriatic acid, 

 even when first precipitated, and before it is dried. Another 

 circumstance which induces me to believe that it is not a hy- 

 drate, is its answering most perfectly the purpose of spongy 

 platina in firing a jet of hydrogen gas, and detonating a mix- 

 ture of oxygen and hydrogen gases ; indeed it appears to me 

 to be an excellent preparation for these purposes, and it is 

 procured with very great facility. 



It is probable that some other metals whose affinity for 

 oxygen is weak, may also be precipitated in the metallic state 

 by the tartrates ; and I have found this to be the case with 

 gold: when tartrate of soda is added to the muriatic solution 

 of that metal, no effect is produced until heat is applied, and 

 then the precipitation of metallic gold is as rapid, and quite 

 as remarkable as that of platina. 



Tartrate of soda being a salt not usually kept, I have some- 

 times employed tartrate of potash : when the solutions are 

 cold, the well-known double salt of potash and platina is preci- 

 pitated ; but on the application of heat the black powder is very 

 quickly formed; the same effect is produced by tartrate of lime 

 and tartrate of ammonia; but neither tartaric acid nor bitar- 

 trate of potash determine precipitation until an alkali is added. 



It appears to me that muriate of platina may be very ad- 

 vantageously employed as a test of the presence of tartaric 

 acid, provided it be first saturated or supersaturated with an 

 alkali. 



During the formation of the black powder, there is an evi- 

 dent evolution of some gas: suspecting it to be carbonic acid 



