268 METALS. 



Describe an- 670. ANOTHER METHOD. The SGCOIld 



other method. me thod is essentially the same as that al- 

 ready described, with the substitution of nitric for sul- 

 phuric acid. The addition of silver, as a preliminary 

 step, is found necessary in this process also. So much 

 silver is added, that the gold forms but a quarter of the 

 mass exposed to the action of the acid. The method 

 is hence called quartation. * The process involves a 

 previous knowledge of the approximate composition 

 of the mixed metal. This may be obtained by the 

 touchstone, as hereafter described. 

 Whatisamal- 671. AMALGAMATION. Gold may be ob- 

 gamation? tained from any material which contains 

 it, even in small proportion, by the process of amalga- 

 mation. This process consists in agitating the finely 

 divided material with mercury, until the latter has ex- 

 tracted all of the precious metal. It is then obtained 

 from its solution in mercury, by the same means em- 

 ployed in the case of silver. This method is employed 

 in the case of the gold-bearing quartz of California. 

 The dust of jewelers shops is similarly treated, in order 

 to save the small proportions of gold which it contains. 

 672. GOLD FROM LEAD AND COPPER. 



How is gold . 



separated Certain ores of lead and copper contain so 

 much old that it; is Profitable to extract it 

 from the metal which they yield. This 

 is done by the processes of liquation and cupellation be- 

 fore described. 



* In the practice of the United States Mint, the addition of less 

 silver has been found sufficient. The proportion of gold is there 

 reduced to one-third. Nitric acid is then employed in the refining 

 process. 



