ipg bESUjuPHURATION OF METALS. 



compared with those that extensive works furnish, though 

 we are well aware, that this would be the best way of attain- 

 ing useful results, the theory of the various operations to 

 which sulphuiets are subjected has not yet been improved 

 by the progress of that science. My object is to supply this 

 defect; and to accomplish it I have collected a great many 

 experiments and observations, that have been long known ; 

 I have added some researches of my own ; and from their 

 examination I have deduced consequences, tl.at^must make 

 .pome alteration in the ideas generally entertained respecting 

 thfi -treatment of metallic sulphurets. 



Sect. I. 

 Of the action of heat on metallic sulphurets. 



Heat always THE action of heat on metallic sulphurets requires first 

 employ to de- to be examined, because it occurs in all the processes em- 

 compose them jpi^y^^ for their decomposition. To appreciate this with 

 accuracy, I have chosen experiments and observations in 

 which this action is completely distinct, which it is of im- 

 portance to remark ; for it is owing to not having analysed 

 the effects produced by various causes, that metallurgists 

 but it has not have ascribed to caloric alone a desulphurating power, 



much effect which it does not appear to me to possess in any verv higli 

 alone. 



degree. 



Suluhnrets of The sulphurets of mercury and arsenic are volatilized in 

 mercury and close vessels, when exposed to a temperature a little elevated. 

 limed by It.' ^^^^ sublimed sulphuret has frequently a different colour 

 from that which has not been sublimed; and the experiments 

 of Proust and Thenard demonstrate, that this change is the 

 consequence of an alteration in the proportions of the ele- 

 ments of the compound. 

 That of iron The native sulphuret of iron experiences but a partial 



not freid from decomposition by means of caloric. By distillation in a re- 

 half its sulphur ' . 1 l/» >I 11 '^ ^ ' T 



ty it. tort we cannot extract halt the sulphur it contams. In 



Saxony the distillation of pyrites in the large way never 

 yields more than 13 or 14 per cent of their weight of sul- 

 phur. ^ 



As these facts were r.ot sufficient to determine my opinion 

 respecting the efl[ects of heat, because all the experiments 



that 



