242 HISTORY OF CALIFORNIA. 



of gold, because of the many readier ways of deter 

 mining the metal, but it seems advisable to state the 

 appearances presented. All the varieties are readily 

 fusible into a globule, which when the gold is pure, is 

 unaltered by the continuance of the heat. In this 

 respect it differs entirely from iron and copper pyrites, 

 which, on being exposed to the flame, give off sulphur 

 fumes and undergo considerable change. In the case 

 of gold containing other metals, these, with the ex 

 ception of silver, may generally be got rid of by con 

 tinuing the heat in the exterior flame with the addi 

 tion of a little nitre. Before the oxy-hydrogen blow 

 pipe, the metal is volatilized in the form of a purple 

 oxide. 



Gold is not acted on by any of the acids alone. 

 When exposed to the mixture of nitric with hydro 

 chloric acid (in the proportion of one part nitric to four 

 of hydrochloric) called aqua regia, it dissolves without 

 residue, the solution giving a purple precipitate with 

 protochloride of tin, and a brown precipitate with pro- 

 tosulphate of iron. Electrum, the mixture of silver 

 with gold above alluded to, is only partially soluble in 

 aqua regia, giving a residue of chloride of silver. The 

 solution is acted on by protosulphate of iron, as already 

 explained. 



The following simple mode of detecting attempts 

 at imposition in gold dust is worthy of being recorded 

 in this place. 



Place a little gold dust in a glass tube or earthen 

 ware saucer, and pour nitric acid upon it; then 

 hold the glass or saucer over a flame, or upon a few 

 embers, until red flames (nitric vapors) arise; if it 

 be pure gold, the liquid will not become discolored ; 

 but if pyrites or brass-filings should have been mixed 



