GOLD. 241 



crystalized in imperfect cubes. Its constituents are, 64 gold, 36 

 silver=100. According to Klaproth, it is acted on neither by 

 nitric nor nitro-muriatic acid. It occurs with massive heavy spar, 

 on ash-grey splintery hornstone, at Schlangenberer, in Siberia. 



Gold is generally separated from accompanying impurities by the 

 process of amalgamation, similar to that described for extracting 

 silver from its ores. After it has been freed by pounding and 

 washing from stony matter, the ore is roasted, to disperse the 

 volatile matter, and oxidize the other metals : it is then amalsia- 

 mated with mercury. The more fluid part of the amalgam is 

 forced through leather, and the remainder subjected to distillation, 

 by which means the mercury is sublimed, and the gold remains in 

 a state of fusion. When the gold is alloyed with silver, the latter 

 metal is removed by parting and qnartatiov. In quartation, one 

 part of the gold is combined with three parts of silver — the object 

 being to reduce the gold to a very minute state of division — and 

 then exposing this compound previously rolled out into thin 

 plates, to the action of boiling nitric acid, which oxidates and 

 dissolves the silver, but leaves the gold in a pure state. 



Pure gold is remarkable for its immutability on exposure to air and 

 moisture, for its bright yellow colour, and for its exceeding ductility 

 and malleability. A single grain of gold may be extended into a leaf 

 which will cover 54| square inches, and not more than 1 -283'OOOth 

 part of an inch in thickness ; excepting platina, it is the heaviest 

 of all known metals, its specific gravity being 19*3. It melts at 

 32 of Wedgewoods' pyrometer, and at a very intense temperature 

 it is volatalized; but it does not appoar to be oxidated by this 

 process. Most metals unite with gold by fusion. None of the 

 acids, except the nitro-muriatic, have any action on gold. A 

 mixture of one part of nitric acid, and two of muriatic acid, has 

 been long known under the name of aqua regia, from its power of 

 dissolving this precious metal. Chromic acid added to the muriate, 

 and aqueous chlorine, also dissolves gold. The solution of nitro- 

 muriate of gold is of a fine reddish -yellow colour ; it tinges animal 

 substances of a deep purple colour; and when concentrated by 

 evaporation, the chloride is slowly deposited in pyramidal crystals. 

 The alkalies, most of the metals, the essential oils, ether, naphtha, 



