490 De sulphur ation of Metals . 
the same combustible, might determine the decomposition of the 
sulphur et. of copper by this metal, at least in certain cases. The 
following experiments, however, did not warrant me in continu- 
ing || this opinion. 
First Experiment . — I made a mixture of ten grammes of 
pyritous copper, the composition of which I knew, with four gram- 
mes of iron filings : I put this into a crucible, covered with char- 
coal in powder, and heated it in the forge for three quarters of an 
hour. The proportion of the iron had been calculated so accurate- 
ly that it was sufficient for taking up all the sulphur combined 
with the copper in the mineral employed. I found in the crucible 
a perfectly homogeneous mass, weighing thirteen grammes, which 
did not contain the smallest globule of metallic copper , nor any ap- 
pearance of separation , between the sulphuret of iron and that of 
copper *. 
Second Experiment Another trial was made by employing 
ten grammes of pyritous copper and five grammes of the same 
roasted mineral. This is nearly the case with the fluxes in which 
the ore or the mattes are not completely desulphurated ; the pro- 
portion of the iron was still sufficient for separating copper, which 
was very abundant in the mixture. I kept up the heat for three 
quarters of an hour, and found, as in the preceding experiment, a 
homogeneous mass, without: any trace of metallic copper, nor of 
pure sulphuret of copper ; this was a real matte of copper. 
Third Experiment. — On this occasion an equal mixture of 
crude pyritous copper, and roasted copper, dipped in olive oil, and 
heated strongly for half an hour in a crucible, presented nothing 
but a powder, which had not undergone fusion, on account, without 
doubt, of the superabundance of the iron. 
I think these few experiments are sufficient for proving that 
the de sulphur ation of copper by means of iron will be always very 
difficult, because there is formed a triple combination between the 
sulphur , iron and copper , or rather a combination between the sul- 
phurets of copper and cf iro?i y which prevents the separation of 
the copper. 
Du sulphur ation of Galena.-— This is one of the sulphurets 
which best yields to the decomposition in question; the fusibility 
bf the lead which facilitates its aggregation, as well as the little affi» 
* In the decomposition of galena by iron , we observe, when the latter is in 
too small quantity, three distinct substances of lead, sulphuret of lead, and 
lastly, sulphuret of iron in the upper part. 
