JJ08 BESULPimRATlON OF METALS. 



Requisite con- success. In order that thef decomposition of a metallic sul- 

 phuret b^ any mineral may constitute the basis of a metal- 

 lurgical pfocess, it is not sufficient, that the affinity of this 

 mineral for sulphur be greater than that of the metal : it ijT 

 farther necessary, beside the conditions economy requires^ 

 that several others indispensable to the success of the process' 

 be satisfied, which greatly diminishes the number of ag'ent^ 

 iudicated by chemistry. For example, if the sulphuret re- 

 fiultintr from the decomposition be infusible, or nearly so; 

 or if it have the property of combining with the metal to be 

 V separated, or witli the sulphuret yet undecom posed ; it is 

 obvious, that the object sought, which is the separation of 

 the metal, will not be obtained. Hitherto scarcely any thing. 

 but lime and iron has been employed. 



Desulphuration of mefcury. 



Sulphuret of The sulphufet of mercury is easily decomposed. It is 



Jnercury by sufficient to present to the sulphur a substance capable of 

 lime or iron. . . . , , , t >•,• i i 



retammg it, and the mercury may be volatilized alone. 



Thus iron and lime are erriployed singly or conjointly in the 



treatment of cinnabarine ores. 



Desulphuration of copper. 

 Cojjper pyrites Copper pyrites afe smelted in some works with lime, 

 hy lime. either in the fourneau a mancfie^ or the reverberatory fur- 



nace ; but this process is not sufficiently known in detail, to' 

 enable us to judge of the efficacy of this agent. 

 tran tfoes not ^ ^*^^^ thought with some metallurgists, that tlie acknow- 

 answer. ledged greater affinity of i ron than of copper for sulphur might 



occasion the decomposition of sulphnret of copper by this 

 metal, at least in some cases : but the experiments lam about 

 to give induced ^ne to relinquish this opinion. 

 Experiment in ^^t E.vp. I mixed 10 gram. {155 grs.] of pyritous copper, 

 proof. the composition of which 1 knew, with 4'3 gram. [66 grs.] of 



iron filings ; put the mixture into a crucible ; covered it with 

 charcoal powder ; and heated it in a forge fire three quarters 

 of an liour. The proportion of iron was calculated so as to 

 be sufficient for taking up all the sulphur combined with 

 the copper in the ore en>ployed. In the crucible I found a 

 perfectly homogeneous mass, weighing 13*1 gram. [202 grs], 

 which dlid not contain the least globule of metallic copper, 



nor 



