Mr. J. Napier on Copper Smelting. 195 



contains a little copjjer, and is ground up and fused. This is 

 generally done along with that from the reducing operation, and 

 the prill from the two added to the assay. 



^Vhen the ores to be assayed are rich in copper, such as sub- 

 sulphui'ets, oxides, and carbonates, there is generally added to 

 the fii'st fusion, when separating the gangue from the metallic 

 portion, a quantity of sulphur, in order to form a regulus or mat 

 of the desired quality, as stated above, which is proceeded with 

 as already described. To fuse carbonates and oxides with sul- 

 phur, and then be at the labour and cost of calcining to get quit 

 of the sulphur again, seems ridiculous. And when these ores 

 have little earthy matters in them, it is unnecessary ; but when, 

 as in many cases, there are upwards of 50 per cent, of earthy 

 matters present, in fusing these with a reducing flux, the liabdity 

 of the oxide of copper to combine with the silica and remain in 

 the slag is so great, that it is found better in practice to take 

 the apparently longest method in order to obtain the most correct 

 results. 



The above is a mere outline of the general method by which 

 the ores of copper are assayed. The following may be said to be 

 a general rule followed in suiting the fluxes, &c. to the kind of 

 ore after assorting. 



Fluxes for different Ores. 



fist heating with a little nitre, quantity 

 depending upon the sulphur and 

 arsenic in the ore. 

 2nd fusing. Fluor-spar, lime, borax, 

 salt, a little argal, quantities accord- 

 ing to the earths. 



1st heating. Nitre, small proportion. 

 2nd fusing. Borax, lime, salt, fluor- 

 spar, and a little argal. 



Black sulphurets . . Same as above. 



ri st fusion. Lime, fluor-spar, and sul- 

 Red and black oxides J phur. 



and carbonates . ."^ 2ndi fusion. Borax, salt, lime and argal, 

 [_ or black flux. 



Native copper . . . Only refined. 



Ground tartar or argal is often used instead of black flux. 

 The black flux is prepared by mixing intimately — 



2 parts nitre, and 



3 parts tartar or argal 



in an iron mortar or other vessel that will stand heat, and insert- 

 ing into the mixture a red-hot iron or red cinder. When rapid 



02 



Yellow sulphurets . < 



Gray sulphurets 



