Gold is the most malleable and ductile metal, as a grain of it can be beaten 
out large enough to cover 54J square inches of 1-280, OOOtli of an inch in thick¬ 
ness, whilst Faraday calculated that the gold from four sovereigns could be drawn 
into wire, would be long enough to reach round the earth at the equator. It does 
not readily enter into chemical combinations with the other elements, and when it 
does the resulting salts are very unstable, being decomposed when brought in 
contact with other metals, metallic salts, organic substances, or by exposure to the 
action of light and air. It is not acted upon by any simple acid, but is dissolved 
by chlorine in solution, or by nitro-hydrochlorie acid forming auric chloride, one 
of its most stable salts. 
Pure gold is so soft that it can be scratched by the finger nail; therefore it has 
to be alloyed with other metals to increase its hardness, silver or copper being the 
most generally employed. An alloy, it must be understood, is not always a 
chemical compound, but simply a mixture of two or more metals in any 
proportions, the English gold standard being an alloy of 1 1 parts of gold to 
one part of copper, but as this is not hard enough for jewellery the proportion 
of copper is greatly increased. The fineness of these alloys is spoken of as so 
many carat gold. Pure gold is expressed as 24, whilst in lower standards the 
number of parts of pure gold in the 24 is mentioned: a sovereign is 22 carat, or 22 
parts gold and 2 copper. 
As gold used in jewellery is mostly of certain standards as 22, 18, 15, or 12 
carats, it. is not necessary to melt it up to tell its fineness, but this can be done by 
marking with it on a black basaltic stone (called a touchstone), then treating the 
mark with dilute nitric acid and comparing it with golds of known standards 
similarly treated. 
Gold also has the property of forming an amalgam with mercury at ordinary 
temperatures, when it forms a soft mass, in which the gold and mercury are found 
to be perfectly mixed. This affinity of mercury for gold is taken advantage of in 
its extraction. 
Eor testing the presence of gold in very minute quantities the mineral is finely 
pulverised and agitated with an alcoholic tincture of iodine; into this solution a 
piece of filter paper is dipped and then burnt, when if the colour of the ash id 
purple it indicates the presence of gold; but this should be confirmed by 
evaporating the alcoholic tincture to dryness and treating the residue with nitro- 
hydrochloric acid, and again evaporating, dissolving the residue in water and 
dropping in a drop of a mixture of stannous and ferric chloride, when a deep 
purple colour will be seen (Purple of Cassius), which confirms the presence of 
gold. Gold may be distinguished from iron pyrites, copper pyrites, and mica, by 
the ease with wbicli it mil cut, with a kinfe. fron pyrites, being as hard as quartz, 
will not cut - copper pyrites will cut, but it yields a greenish powder; whilst mica 
splits oft m sliming scales. J 5 
., Auothe , r “f lod ’ wl “ w fc l le 8 P ecks aru too to trv them with a knife, and 
acids are not at, hand, is to make the stone red-hot, and either let it cool or drop it 
into cold water, when the iron pyrites will turn red, the copper 1,lack, and the 
oT meltinu thc tohl " ^ g ° W WlU n ‘ maiu lmaUu red. Then) need he no fear 
ordinary fire Sd ’ ’ re< * mres 11 mu,; h higher temperature than that of an 
, ! )US1,1 J; S keing valuable as a medium of exchange, is one of the most 
SS facUw'it a° neW 1 ery f Ca Ti b6 8Ur P a8Bed ’ owing to its beautiful colour. 
ako uL? LLlt l, i r ’ i,U< 4® .ease with which it can be worked. It if 
also, used largely for plating and gilding, in both of which processes it was 
SfoXl f 1 i f0 + T° f le f’ bu V lw R is found much more economical 
when the article to be plated is metal, to deposit a thin coating of gold from solu 
tion upon it by means of an electric current, by which l vow thin filn «■ i 1 n 
be evenly deposited over a large surface, doll Tiid 'ffl thr SmlfgiS 
