479 
De sulphur ation of Metals. 
The nature and properties of these compounds are well known, 
since chemists have so frequently made them an object of enqui- 
ry. The facts, however, collected in laboratories have never been 
carefully compared with those furnished by the workshops, al- 
though it is very well known that the latter description of experi- 
ments furnish the most useful results ; and the theory of various 
operations to which we subject the sulphurets, has not kept pace 
with the relative progress of science. It is my intention, in the Me- 
moir, to supply what is wanting in this respect : for this purpose, 
I have made various experiments, and collected several observa- 
tions long known : to these I have added some reflections peculiar 
to myself, and have deduced from their examination, consequen- 
ces which may be productive of some changes in the ideas gene- 
rally entertained respecting the treatment of the metallic sulphu- 
rets. 
§ Of the Action of Heat ujion the metallic Snlfihurets. 
The action of heat upon the metallic sulphurets should be 
first examined, because it is to be met with in all the operations 
by which we seek to decompose these substances : in order to ap- 
preciate it in a precise manner, I have made choice of experi- 
ments and observations in which this action is entirely isolated, 
which is worthy of observation ; for it is because we have-not ana- 
lysed the effects produced by several 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 sulphuretis frequently altered 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 compound. 
The native sulphuret of iron (pyrites of iron) undergoes a par- 
tial decomposition only from the caloric : by distilling it in a re- 
tort, 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 sulphurf. 
These facts not being sufficient to decide my opinion upon the 
effects of heat, because all the experiments which have come to 
* Proust, Journal ds Physique, tome liii. 
t Schlutter , tome ii. p. 228, of the French translation. 
