214 On the De-sulphuratton of Metals, 



live progress of science. It is my intention, in thisMcmpir, 

 to supply what is wanting in this rcspecl : for this pur- 

 pose, I have made various experiments, and collected seve- 

 ral observations long known : to these I have added some 

 reflections peculiar to myself, and have deduced from 

 their examination, consequences which may be productive 

 of some changes in the ideas generally entertained respecting 

 the treatment of the metallic sulphurets. 



§ I. Of the Action of Heat upon the metallic Sulphurets. 



The action oiheat upon the metallic sulphurets should be 

 first examined, because it is to be met with in all the ope- 

 rations by which we seek to decompose these substances : 

 in order to appreciate it in a precise manner, I have made 

 choice of exi)eriments and observations in which this action 

 is entirely isolated, which is worthy of observation ; for it 

 is because we have not analysed the effects produced by se- 

 veral causes, that we have been led, in metallurgy, to ascribe 

 to caloric alone a de-sulphurating power, which it does not 

 seem to possess in any great degree. 



The sulphurets of mercury and of arsenic are volatilized 

 in close vessels, when they are exposed to a temperature 

 somewhat raised. The sublimed sulphuret is frequently al- 

 tered in its colour ; and the experiments of Messrs. Proust 

 and Thenard show that this change is the consequence of a 

 variation in the proportion of the elements of this com- 

 pound. 



The native sulphuret of iron (pyrites of iron) undergoes a 

 partial decomposition only from the caloric : by distilling it 

 in a retort, we cannot extract from it the half of the sulphur 

 which it contains *. In Saxony, the distillation of pyrites 

 upon a large scale never yields more than from 13 to 14 

 per cent, of sulphur f. 



These facts not being sufficient to decide my opinion 

 upon the effects of heat, because all the experiments which 

 have come to my knowledge were made at a tempera- 



* Proust, Journal de Physique, tome liii. 



f Srhlutter, tome ii. p. 228, of the French translation. 



ture 



