GOLD. 267 



In solution, it is also employed as a hair dye, and in 

 the production of indelible ink. 



GOLD. 



Mention some 668. DESCRIPTION. Gold is a yellow 



properties of meta i o f brilliant and permanent lustre. 



gold? Its sol- 



vent? and Its extreme malleability is strikingly illus- 



occurrence? 



into a leaf but little more than ^J of an inch in 

 thickness. As the fact may be otherwise stated, a cube 

 of gold, five inches on a side, could be so extended as 

 to cover more than an acre of ground. Such gold leaf 

 is permeable to hydrogen. A jet of this gas may be 

 blown through it and kindled on the opposite side. 

 Gold is proof against all ordinary acids, excepting aqua- 

 regia. It is found only in the metallic state, and com- 

 monly either in quartz rock or in the sands of rivers. 

 Native gold contains from five to fifteen per cent, of 

 silver. 



How is pure ^69. PRODUCTION. - THE REFINING PRO- 



goid produced? CESS . Native gold may be freed from the 

 silver which it contains, by the agency of concentrated 

 sulphuric, or nitric acid. A difficulty in accomplishing 

 this result arises from the fact that every particle of silver 

 is so perfectly surrounded by gold, that the acid does 

 not readily reach it. This difficulty is overcome by 

 fusing more silver into the gold, and thus opening a 

 passage for the solvent. This being done, both the 

 original silver and that which has been added, are read- 

 ily removed. The above is the process at present pur- 

 sued in France for refining gold. 



