Chap. 35;] Standard of Gold Coin. 237 



There are fcarcely any metals with which gold will 

 not unite. When boiled a Ihort time with mercury, 

 it forms an amalgam which is gritty and rigid at the 

 firft, but which becomes by grinding more foft and 

 tender ; this is often made ufe of for gilding the fur- 

 face of filver and copper, as was more particular]^ 

 mentioned when treating of the latter metal. -* 



Gold readily unites with zinc, and produces a mixed 

 metal, whiter than might be expected from the quan- 

 tity of zinc which is employed j this alloy, made with 

 equal parts of the two metals, is remarkably fpkndid, 

 is of a fine grain, and is not liable to tarnifh : on ac- 

 count of thefe properties it has been recommended for 

 conftructing the mirrors of telefcopes. 



All the metals, except filver 'and copper, take away 

 the ductility of gold, but none more remarkably than 

 tin, a grain of which added to a thoufand of gold is 

 faid to deprive it entirely of ductility. Copper is 

 commonly ufed to alloy gold, as filver renders it very 

 pale. Copper rather heightens the colour of gold, but 

 inclines it to red. 



Goldfmiths denote the finenefs of gold by the word 

 carrat. It is fuppofed to be divided into twenty-four 

 parts, called carrats ; and gold, which is quite free 

 from alloy, is faid to be twenty-four carrats fine; that 

 which contains one twenty-fourth of alloy is called 

 gold of twenty-three carrats i that which contains two 

 twenty-fourths, of twenty-two carrats, and fo on. In 

 England, the ftandard of gold coin is twenty-two car- 

 rats fine geld and two carrats of alloy, which latter is 

 half filver and half copper. The French, Spanifh, and 

 Flemifh gold are nearly of the fame fineness, 



