923 Transactions of the American Institute. 



has been estimated at 2016 degrees F. It is, therefore, less fusi- 

 ble thau either silver (1873 degrees F.) or copper (1996 degrees 

 F). Ill fusion it exhibits a bluish greeii color. Gold contracts on 

 cooling, and cannot advantageously be employed for castings. 

 Native gold affords numerous well defined crystals belonging to 

 the cubic system; and of these the greater number is affected by 

 the faces of the regular octohedron. 



Gold has a peculiar metallic luster, which, if once seen, can 

 scarcely be mistaken. Its malleability and equally reflected light, 

 when held at varying angles, distinguishes gold from pyrites and 

 sulphurets. 



The following are the chemical tests given by Muspratt: 



SulpJiate of iron gives, in acid solution, a brown precipitate. If 

 very dilute solution, only a blue coloring. 



Protochloride of tin: In dilute solutions a purple red coloring; 

 when strong, an almost brown precipitate. 



Metallic zinc precipitates metallic gold as a voluminous brown 

 precipitate. 



Potassa in excess: No precipitate; after some time a green color- 

 ing and slight precipitate. 



Ammonia: Yellow precipitate of fulminate of gold. 



Carbonate of soda or potassa: No precipitate in cold solutions, 

 but when heated, voluminous precipitate, like oxide of iron. 



Bicarbonate of the same: No precipitate. 



Carbonate of ammonia: Behaves like amiponia, carbonic acid 

 being evolved. 



Oxalic acid: Dark, greenish black precipitate, more quickly pro- 

 duced by heat. 



Tartaric acid and tartrate of soda: Dark precipitate when boiled. 



Sulphide of ammonium and sulphu7Tetted hydrogen: Dark brown 

 or black precipitate. 



The usual tests for silver are the following: 



Potassa: Brown precipitate; becomes black on boiling. 



Carbonate of soda or potassa: White precipitate, soluble in 

 excess of ammonia. 



Carbonate of ammonia: White precipitate, soluble in excess of 

 the same. 



Phosphate of soda: Yellow precipitate, soluble in ammonia. 



Oxalic acid: In neutral solution a white precipitate. 



Sulphuretted hydrogen and sulphide of ainmonium: Black pre- 

 cipitate. 



