Assaying Ores of the Precious Metals. 



65 



will be delicate or strong according to the weight of the 

 valve. 



With a Bunsen's blow-pipe, provided as it is with an air- 

 jet in addition to the ordinary gas jet and collar of the 

 common Bunsen's burner, and with this automatic blast, 

 gentle or strong at will but always steady, the assay er has 

 such complete control over the proportions of air and gas 

 in his flame that he is able to regulate the heating, the 

 oxydizing and the reducing power of it at his pleasure. 

 With a flame so reliable in these respects and at the same 

 time so large as this one may be made, the assayer is able 

 to scorify and cupel a quantity of ore quite as large as 

 would be taken for a furnace assay. The heat of the flame 

 is sufficiently intense to keep the scorifyer and cupel in a 

 glow, needing no assistance from other sources, but if these 

 vessels are placed over the flame of a laboratory lamp its 

 heat will facilitate the operation by allowing the energies 

 of the blow-pipe to be directed more exclusively to the 

 chemical actions which it is required to produce. 



The accuracy of the assay made by this method has been 

 found by comparison with assays of the same ores, both by 

 the furnace and b*y solution to be satisfactory. In any la- 

 boratory where water and gas are abundant this method 

 will be found easy, elegant and exact. 



[Trans, vii.'] 9 



