i2.04 DESULPHURATION OF METAI.S. 



ed together in filrtwly. When the retort was redhot, a pretty considerable 



p retort, quantity of sulphurous acid gas was evolved; and this conr 



tinned for an hoyr, at the expiration of whicli the retort 



The result a began to melt. The residuum had been fused, and wa» 



^'T'ViT ^^^^'^ to be a mixture of oxide and sulphate of lead. I 

 Jd;. & sulphate. . , . ^ . 



satisfied myself, that the sulphurous acid, which had been 



received into water, was not mixed with any sulphuric. 



The sulphate This experiment proves the possibility of the decomposi- 



^ecomposed ^j^^^ ^f ^j^^ Sulphate of lead by the sulphuret ; or rather that 



by the sulphu- c ^ l 



ret. of the sulphuric ^cid it contains by the sulphur and lead of 



the galena. The sulphurous acid arises no doubt equally 



from the oxigenation of the sulphur, and the semidecom- 



position of the acid ; for I convinced myself, that the re»ir 



Equal parts duum contains no sulphate. I repeated the process with 



*^?h^*^^^^"^ equal parts of galena in sulphate, when the evolution of 

 sulphurous acid was still more abundant, and what remained 

 in the retort was a mixture of oxide and sulphuret. Hence I 

 concluded, that, if tlie proportion of sulphuret of lead were 

 too small in the former experiment, it w^as too large in this* 

 I made also an attempt to ascertain more nearly the propor- 

 tions, that would exactly effect the mutual decomposition ; 

 and at the same time I endeavoured to satisfy myself of the 

 oxidation of the lead contained in the galena in the metallic 

 state. 



14 parts to 8. With this view I put 14 gram, of sulphate and 8 of sul- 

 phuret, well mixed together, into a crucible, not lined, 

 which I suffered to grow redhot undisturbed. I observed. 



Sulphurous that a considerable ebullition took place, occasioned by the 

 evolution of sulphurous acid; and I did not withdraw the 

 crucible, till the matter was in quiet fusion. When cold I 



Result, sul- found two distinct substances; one, which was at the bottom, 



^tasroHead ^'^nsisted entirely of sulphuret of lead, that had been fused, 

 without any mixture of ductile lead ; the other exhibited all 

 the characters of the oxide called glass of lead, and was 4 

 compound of oxide and silex from the crucible, without any 

 indication of sulphate of lead. 



This experiment convinced me, that the le£^d of the ga- 

 lena had been oxided at the expense of the sulphuric acid : 

 but it did not show the quantity of galena necessary for the 



Sulphuret 1 complete decomposition of the sulphate. I believe, how- 

 ever. 



