352 On some Combinations of Platina. 



The aqueous solution of sulphate of platina, as M. Proust 

 has stated, is not precipitated by muriate of ammonia j but 

 if the solution be boiled to dryness, the yellow compound 

 is formed. 



The sulphuric acid cannot, it would seem, be separated^ 

 from the aqueous solution of sulphate of platina, by any of 

 the common methods, even though an excess of nitric acid 

 is present. Acetate and nitrate of lead occasion in it a dark 

 brown coloured precipitate, which I have not examined, 

 but which is probably a triple compound of the oxides of 

 lead and platina with sulphuric acid. 



When the dry sulphate of platina is heated to redness ia 

 close vessels over mercury, it is entirely decompounded j 

 the platina remains in its metallic state. The gaseous 

 products are oxygene gas, with a little sulphureous acid 

 gas, and a fluid is obtained which evolves copious white 

 fumes when exposed to the atmosphere, and is probably 

 concentrated sulphuric acid, impregnated with sulphureous 

 acid gas ; — a fluid precisely analogous to the glacial sul- 

 phuric acid of some authors. 



Analysis. 



To determine the composition of this substance, I de- 

 compounded it by the agency of heat, in small retorts over 

 mercury, and over water ; and from a comparison of the 

 results furnished by both methods, I shall venture to state 

 the proportions of its constituent parts. 



I hoped to have been able to separate all the acid from 

 the sulphate of platina by heat, and thus to have obtained 

 the pure oxide alone ; but this was quite impracticable, as 

 both the oxygene and acid appeared to be expelled at the 

 same temperature. In analysing this substance, some pre- 

 cautions were necessary, to avoid the powerful agency of 

 the atmosphere on it. — It could not be pulverized and 

 transferred to any vessel, or weighed, without acquiring an 

 increase of wei;^ht. — The dry cake of sulphate of platina 

 was therefore broken into small pieces whilst it was quite hot, 

 and then exposed to the utmost heat of a lamp for about 

 two hours. It was then hastily transferred into a very small 

 ground stoppered bottle previously dried and heated. The 

 bottle was now poised in a very delicate balance, and some 

 of the sulphate put into a small warm retort ; the weight 

 the bottle had lost, indicated, of course, the quantity of sul- 

 phate which had entered the retort; the minute portion of 

 air could make no ascertainable difference in the results. 



Barometer 



