AGRICULTURAL SSBSEUrrf llT 



When coppei' is combined with sulphur in an ore, it 

 il in its metallic form ; in dissolving' in an acid, its oil rises 

 in vapour ; or vapours produced by the decomposition of 

 tliis oil occasion an effervescence. 



Alltlie calces of copper! have tried ;ire combined 

 with gas^ respirable air, or other vapours, excepting one, 

 which is of a light gTecn colour, brittle, and which breaks 

 smooth like glass ; ij, specimen of it is contained in JDr. 

 Hunter's mnsenm : this dissolves without effervescexice, 

 the others all eftervesce. A boiling-heat is necessary to 

 render the solution complete, ot which grent care is to 

 be taken. 



If there be any sulphur in the ore, it appears quite 

 ciear,^n jumps ; a small portion of it, however, is de- 

 stroyed by the nitrous acid. Earthy matters insoluble 

 in acids, if any, and arsenic, appear in a powder at the 

 bottom. If there be any silver, it is mixed with this pow- 

 der, and is to be extracted by melting it with black flax 

 ^nd Uthargc, and cupelling in the common way. If there 

 be any goJd, it may be taken out of the solution by 

 jether. 



When the copper is combined with nitrous and muria- 

 tic acids, it might be thought suiiicient to apply the iron 

 immediately ; but it is much more convenient to precipi- 

 tate it from them, and combine it with vitriolic aeid, on 

 account of the convenience of washing the precipitate, 

 which is in a ^lore .compacted mass. 



If there be any calcareous earth dissolved, the vitri- 

 olic acid will combine with it, and form a white powder^ 

 which will be left after the copper is re- dissolved, and 

 be separated carefully from the solution. 



After the precipitation of the copper, it is necessary to 

 get rid of the salts pcrfectlj', before we apply the vitrio- 

 lic acid; otherwise part of the copper would be re dis- 

 solved. 



Vitriolic acid^ili not dissolve copper in its metallic 

 form, and may be applied to dissolve any iron that may 

 be mixed with the precipitate, as well as to loosen cop- 

 per, whicUsometiaiCs adheres to tho iron. 



