1870.] On the Method of Assaying Silver. 387 



heat. The metallic silver so recovered is transferred to the 

 Mint. 



Under the circumstances of the solution and of the precipitation 

 as detailed above, should any gold happen to be present in the sam- 

 ple operated on, it is not dissolved, and therefore becomes entangled 

 with the precipitated chloride of silver and dried and weighed with 

 it, and accordingly comes to be regarded and valued as silver. In 

 this the chloride process resembles that by cupellation, which like- 

 wise takes no distinguishing cognizance of gold, and both these 

 processes contrast in this respect with the volumetric one which is 

 a rigid analysis for silver alone ; so that, strictly speaking, an assay 

 conducted by either of the first-named methods ascertains the 

 proportion present of " the precious metals," i. e. silver and gold.* 



Should mercury be present it does not interfere with the result, 

 when the solution has been effected in excess of nitric acid with 

 strong heat. Thus the mercury becomes peroxidized, and hydro- 

 chloric acid forms no precipitate in solutions of mercuric salts : 

 any mercuric chloride resulting from the combination would re- 

 main in solution, and be washed away in the course of the process. 



Should lead happen to be present, hydrochloric acid gives no 

 ■precipitate in a dilute solution, the chloride of lead being soluble 

 in a certain proportion of distilled water : but even were the pro- 

 portion of lead to silver tolerably large, and the chloride of lead 

 happened to be thrown down, the repeated washings would dis- 

 solve and get rid of it. 



With regard to the weight of the small portion taken to re- 

 present the mass, the system prevails in the Indian Mints of 

 taking samples for assay by granulating a small portion of the 

 contents of each melting pot ; when the metal is in a thorough 

 state of fusion and has just been well stirred, a small ladleful 

 of the molten metal is quickly poured from a tolerable height into 



* Much of the silver which finds its way to the Indian Mints is rich in gold ; 

 for instance sycee contains on an average somewhat about 12 grains in the 

 Troy pound. This in minting operations is considered as silver, and as such 

 it enters into the coinage. There being as yet no refineries established here, 

 through which such silver could pass to the Mechanical Departments of the 

 Mints, the silver coins made during a period when a heavy importation of 

 sycee had been worked up, contain as much as 4 or 6 grains of gold in every 

 32 tolas or 1 ft Troy. 



