ON THE METHOD OF MAKING GOLD-ASSAYS. 



No. II. 



221 



No. Ill, 

 Gold-assaying. 



The process of gold-assaying comprises six distinct operations : — 



1st process. — The portion of metal to be assayed is adjusted to an exact 

 ■weight by cutting and filing. 



2ncl process. — The accurately -weighed portions of alloy are added to 

 molten admixtures of lead and silver contained in porous cups or " cupels " 

 of bone ash, which are arranged in rows in a muffle or small oven. The pro- 

 portions of the latter metals are calculated so as to bear a definite relation 

 to the supposed amount of gold and base metals present in the aUoy. 



Resxdt. — The lead oxidizes and is absorbed by the porous " cupel," together 

 with the copper and other oxidizable metals, and the silver and gold remain 

 in the form of a button, which may also contain platinum, iridium, or metals 

 possessing similar properties. 



3rc? jjrocess. — The button is reduced by rolling to a thin strip, which is 

 annealed and bent into a loose coil or " cornet." 



4tk process. — The " cornet " is placed in nitric acid of the specific gravity 

 of 1-25, and the acid is maintained at incipient ebullition for 15 minutes; 

 the coil is then treated in a similar manner with nitric acid of specific 

 gravity 1-4. 



