270 CHEMISTRY. 



Its properties are, a splendid yellow color, brilliancy, high 

 specific gravity, softness, great malleability and ductility, 

 and indisposition to combine chemically with other sub- 

 stances, especially oxygen. Gilding is usually performed 

 by means of gold-leaf, except in case of the metals, on which 

 it is commonly done by amalgamation, a process just ex- 

 plained. Gold is so soft a metal that it is not fit for use 

 in its pure state, and is therefore always alloyed with sil- 

 ver and copper to give it the requisite hardness. The 

 gold coin of this country is one-tenth part an alloy of silver 

 arid copper. The word carat, used so much in express- 

 ing the degree of purity in specimens of gold, signifies one 

 twenty-fourth. If, therefore, it is said of any specimen of 

 gold that it is 18 carats fine, it means that the pure gold 

 in it is 18 parts out of the 24, or that it is three fourths 

 gold. Perfectly pure gold is, of course, 24 carats fine. 

 The word is of Eastern origin, and comes from a word 

 meaning bean. 



Gold is not soluble in nitric acid, nor in hydrochloric, 

 but in a mixture of the two it dissolves readily, as ex- 

 plained in 225. 



383. Chloride of Gold. This salt can be made in two 

 ways. If gold-leaf be put into chlorine water, the chlorine 

 will unite with it, and chloride of gold will be found in the 

 solution. But it is most commonly made by treating gold 

 with aqua regia. The chemical action is described in 225. 

 If the solution thus obtained be evaporated, a brownish-red 

 salt will appear, which is the chloride of gold. It is very 

 easily decomposed, as can be shown by the following exper- 

 iment : Dip a test-tube which has been wiped dry into a 

 dilute solution of chloride of gold, and then heat it over a 

 spirit-lamp. It will become gilded, showing that heat suf- 

 fices to disengage the chlorine from the gold. The chloride 

 of gold is quite in contrast with the chloride of sodium in 



