GOLD. 407 



gerous in inexperienced hands. It is also prepared by dissolving silver in 

 nitric acid, and adding alcohol. It cools in crystals. Fulminating mercury 

 is prepared in the same way. 



GOLD is the most valuable of all metals, the " king of metals," as 

 it was termed by the ancients. It is always found " native," frequently 

 with silver and copper. Quartz is the rock wherein it occurs. From the 

 disintegration of these rocks the gold sands of rivers are formed, and 

 separated from the sands by "washing." In Australia and California 

 " nuggets " are picked up of considerable size. 



It is a rather soft metal, and, being likewise costly, is never used in an 

 absolutely pure state. Coins and jewellery are all .alloyed with copper and 

 silver to give them the requisite hardness and durability. Gold is extremely 

 ductile, and very malleable. One grain of gold may be drawn into a wire 

 five hundred feet in length, and the metal may be beaten into almost 

 transparent leaves -JOCMJOT f an mc ^ m thickness ! 



Aqua-regia, a mixture of hydro- 

 chloric and nitric acids, is used to dis- 

 solve gold, which is solved only by selenic 

 acid, though the free chlorine will dissolve 

 it. Faraday made many experiments as 

 to the relation of gold to light. (See 

 "Phil. Trans.," 1857, P- US-) The 

 various uses of gold are so well known 

 that we need not occupy time and space 

 in recording them. Gilding can be 

 accomplished by immersing the articles 

 in a hot solution of chloride of gold and 

 bicarbonate of potash mixed; but the FI S . ^.-Native gold. 



electro process is that now in use, by which the gold precipitates on the 

 article to be plated. 



We have already described the process of electro-plating in the case of 

 silvered articles, and we need only mention that electro-gilding is performed 

 very much in the same way. But gilding is also performed in other ways ; 

 one of which, the so-called water gilding, is managed as follows. Gilding 

 with the gold-leaf is merely a mechanical operation, but water-gilding is 

 effected by chemistry. 



Water-gilding is a process (in which, however, no water is used) for 

 covering the surface of metal with a thin coating of gold ; the best metal 

 for water-gilding is either brass, or a mixture of brass and copper. A 

 mixture of gold and mercury, in the proportion of one part of gold to eight of 

 mercury, is made hot over a fire till they have united ; it is then put into a 

 bag of chamois-leather, and the superfluous mercury pressed out. What 

 remains is called an " amalgam " ; it is soft, and of a greasy nature, so that 

 it can be smeared over any surface with the fingers. The articles to be gilt 



