©ESUI>5IIURATI0N OF METAXS. £tOI 



of all roaslincrs, sis well as by the manner in which the prOf 

 .cess is conclnrtcd. In the roasting- of snlphurets, instead 

 of seeino' the volatilization of the sulphur effected by a mo- 

 <derate and long continued heat, we find a sulphuret decom- 

 posed by the simultaneous action of caloric and air : and 

 the acknowledj^ed necessity of not fusing the ore, instead of The ore must 

 iirising from the fear of communicating to it by liquefaction "^^^f^!j^J^2^'^ 

 a cohesive force capable of resisting the separation of the 

 ^sulphur, will be ascribed more simply to this circmnstance, 

 that s:i(h a state will confine the action of the air to a sur- 

 face that cannot be renewed, and will soon be covered with - 

 A metallic oxide. The combination of oxigen with the ele- 

 ments of sulphurets gives rise to oxides and acids, the affi- 

 nities of which have great influence on the separation of the 

 sulphur, and the results of roasting; which are commonly a 

 jnixture of an oxide, a sulphate, and undecora posed 5ul- 

 phmet. I shall now examine more particularly and sepa- 

 rately the roasting of sevei*al kinds of sulphurets, because 

 the nature of the metal greatly modifies the results; and I 

 ^hall afterward point out how the sulphur is separated, and 

 in what form. 



Roasting of copper pyrites. 



Pieces of pyritous copper are laid on billets of wood in Co])per py- 

 the most convenient manner for the combustion to continue '^'^^'^* 

 ^ long time. The first heat separates part of the sulphur. Sulphur rises, 

 which is in some degree sublimed, and may be collected ; 

 but afterward it becomes the combustible, that serves by bums, 

 burning to continue the operation; and sulphurous acid is sulphurous 

 dksengtiged, the elasticity of which, being augmented by acid flies oft, 

 the increase of temperature, prevents its combiimtion with 

 the metallic "oxides. The sulphuric acid, tliat is formed ^^'-'ph ate of 



notwithstandi'igthe care taken to moderate the combustion, ^^i^P'^^f^^^^ed, 



'^^ , ^ , ' ana ot iron 



unites with the oxides of iron and copper, but the sulphate which is agaih 

 of iron is in part decomposed by the superoxidation of the "^ P^rt decora- 

 metal. 



Iron pyrites subjected to the same operation will undergo Iron pyrites. 

 similar decompositions in the same order. 



The roasting of cupreoug pyrites in the revcrberatory fur* Copper pyrites 

 nape gives rise to the same phenomena, and mi«ht be sup- rator*^ T^^*^^^^ 



posed 



