DESULPIHTRATION OF METAtS. ' gO/ 



tallic sulp]uirets,the upper partof lnt>b furnaces would be well 

 adapted to the roasting of ores ; for, beside that the tempe- 

 rature there is not too great, the air that comes thither, being 

 deprived of part of its oxigen, scarcely forms any of those 

 sulpluites, that oppose the separation of the sulphur. But 

 th€ fact is the reverse of this, which is to me an additional 

 proof of the little effect of the action of caloric alone on 

 these substances. The sulphur is separated, from the sulphu- 

 rets, as has been seen, in the state of sulphurous acid, and 

 oxigen is indispensable to its formation. In furnaces of no Advantages of 



G^reat heisfht the air that comes into contact with the fresh ^ J^werfur- 



. . , nace. 



charge of ore still contains a great deal of oxigen, and the 



sulphurous acid formed is soon withdrawn from the dis- 

 oxidiug jaction of the charcoal : but if a small portion be de- 

 composed, a fresh sulphuret is formed, which is afterward 

 roasted in the same manner as the ore. In the Scotch fur- 

 nace for instance, when any matts flow from it, they are im- ^ 

 mediately thrown into the furnace again, and what escaped 

 decomposition in the first process is decomposed in a second. 

 In high furnaces on the contrary the ore placed in the upper Disadvantage 

 part undergoes a very incomplete desulphuration, because ^^^^'^'^^^S^^" 

 the air coming into contact with it contains but very little 

 free oxigen ; the sulphurous acid formed in the Interior is far 

 the greater part decomposed in traversing all the height of 

 the furnace fdled with coals, and a sulphuret is recomposed ; 

 this by its gravity tends to descend into the basin, which it 

 does not reach till after a succession of decompositions ; and 

 the consequence must be a considerable loss of metal, as in 

 fact is observed. 



All these facts together seem to me to place it beyond These proofs 

 doubt, that the decomposition of metallic sulphurets j^ '^^^^^"^'^'^>'^^' 

 roasting is produced by the oxigenatioii of their component 

 parts, and the sulphur is separated more or less completely ia 

 the state of sulphurous acid. 



Sect. III. 

 Desulphurdtion of metals independently of the action of the air* 



The I'arious affinities of sulphur for different mineral sub- Desulphura- 

 stances afford means of decomposing certain sulphurets, and tion by electiye 

 metallurgists have already availed themselves of several with 



success. 



