230 Quartation. [Rook VI. 



gold by cupellatton ; but in order to feparate filver 

 from it, other procefles muft be employed. The beft 

 of thefe is called quartation, becaufe the gold muft not 

 exceed the fourth part of the weight of the mafs fub- 

 mitted to trial. The gold, therefore, muft be firft 

 mixed with three times its weight of filver, the effect 

 of which is, that the particles of gold are removed to 

 fuch a diftance that they cannot protect the filver 

 from being acted .on. The mafs of gold and filver 

 being then beaten out into thin plates to increafe the 

 furface, are expofed to the action of aqua fortis, which 

 diilblves the iilver, and leaves the gold in a fpongy 

 mafs ; this is warned two or three times with aqua 

 fortis, and then expofed to heat in a muffle *, to 

 recover its metallic brightnefs. When filver is thus 

 feparated by aqua fortis, a minute portion of the filver 

 is apt to adhere to the gold, and, therefore, when it 

 is an object to have the gold perfectly pure, it is 

 proper to fubmit it to the action of aqua regia, which 

 dUTolves the gold, and converts the filver into luna 

 cornea, which is precipitated to the bottom of the 

 veffel. When it is intended to feparate filver by aqua 

 regia, the proportions of the metals muft be reverfed, 

 and as the gold is to be difTolved, it muft be three times 

 the weight of the filver. 



In this way gold may be obtained quite pure ; but 

 the goldfmiths find a difficulty in obtaining it per- 

 fectly ductile. To have it foft and tough it muft 

 be melted with a ftrong heat, and afterwards cooled 

 vry (lowly. 



In applying faline fubftances to gold, it is found that 

 ho one of the acids, in its ordinary ftate, produces the 



* A fmall earthern oven made and fold by the crucible manu- 

 facturers. 



leaft 



