On some Combinations of Platina, fill 



drogen in the metallic state. M. Proust considered it as a 

 sulphnret, and first noticed a singular property it has of 

 forming sulphuric acid whilst drying in the atmosphere*. 

 This fact has since been observed by Professor Berzelius of 

 Stockholm, as he lately informed me. In operating on 

 this substance, I soon had occasion to verify the preceding 

 observation of those able chemists ; for in cases when it 

 was dried on paper, at the moderate heat of a sand-bath, 

 the paper was burnt by the acid and entirely destroyed. 

 When it was dried at the common temperature of the at- 

 mosphere, a quantity of acid was also formed. It may not 

 be miproper brieflv to describe this substance after it has 

 been dried at a gentle heai in the air, and when of course 

 it has undergone partial decomposition. 



Its colour is black ; it is in small pieces, the particles of 

 which are loosely coherent. It is destitute of lustre. It 

 marks the fingers or paper, but the lustre is much interior 

 to that of plumbago. It has a strong acid taste. It is de- 

 stitute of smell. When heated just below redness on a 

 thin slip of platina, it deflagrates, emitting red sparks, and 

 is partially decomposed ; by exposing it to a red heat for 

 some minutes, sulphureous fumes are copiously emitted, 

 and the platina remains in a state of purity. It appears to 

 be unaffected by boiling muriatic or sulphuric acid. It is 

 soluble with some little difficulty in boiling nitro-muriatic 

 acid. It is rapidly decomposed, with vivid ignition, when 

 heated with oxymuriate of potash. When it is heated in 

 close vessels over mercury, the products are water, sul- 

 phureous acid gas, a minute quantity of sulphur, and a 

 substance analogous in its phvsical and chemical properties 

 to the subsulphuret of platiua which I have already de- 

 scribed. I shall state one experiment which seems to 

 prove this fact. Some hydro- sulphuret which had been 

 drying for some days on a sand-bath in a platina crucible, 

 was heated to redness in a retort over mercury : during the 

 process it became partially ignited : the products were si- 

 milar to those above meuiioned : ten grains of the residual 

 Bubsiance were decomposed at a red heat in a platina cru- 

 cible, and furnished S'S grains of pure platina. This givt||# 

 its compsition bb platina, ' 



15 sulphur, 



100 ; 

 and if allowance be made for a minute quantity of sulphuCv 



* Aitnaiit lit Chimie, torn* xlis. pb iW- ' 



3 expelled 



