GOLD. 
of reflecting teleseopes, on account of the 
fine polish it is susceptible of, and its not 
being subject to tarnish. The alloys of gold 
with molybderia are not known. It could 
not be mixed with tungsten on account of 
the infusibility of this last substance. Mr. 
Hatchett gives the following order of dif- 
ferent metals, arranged as they diminish the 
ductility of gold ; bismuth, lead, antimony, 
arsenic, zinc, cobalt, manganese, nickel, tin, 
iron, platina, copper, silver. The first three 
were nearly equal in effect ; and the platina 
was not quite pure. 
For the purposes of coin, Mr. Hatchett 
considers an alloy of equal parts of silver 
and copper as to be preferred, and copper 
alone as preferable to silver alone. 
Gold is found mostly in the metallic 
state, though generally alloyed with silver, 
copper, iron, or all three. It is found 
either in separate lumps, or visible grains, 
among the sands of rivers, in many parts of 
Europe and elsewhere. The quantity is, 
for the most part, insufficient to pay the 
cost of separating it ; but it is thought to 
be more universally diffused in sands and 
earths than any other metal, except iron. 
The greatest quantity of gold is imported 
into Europe from South America. Some 
is brought from the East Indian islands 
and China, and some from the coast of 
Africa. The principal gold mines in Europe 
are those of Hungary. Some sands afford 
gold by simple washing; the heavy metallic 
particles subsiding soonest : but when it is 
bedded in earths, or stones, these substances 
are pounded, and boiled with one-tenth of 
their weight of mercury together with 
water. The mercury, after a certain time, 
* absorbs the gold, and may be separated by 
pressure through leathern bags, and sub- 
sequent distillation. Or, otherwise, if the 
sand be heated red hot, and quenched in 
water several times, for the purpose of 
cracking and dividing it, and the whole be 
then melted into glass, with twice its weight 
of the oxide of lead called litharge, and 
charcoal powder be then added, the lead 
will be revived in the metallic state, and 
will carry the gold along with it. By ex- 
posure to a proper degree of heat, with 
access of air, the lead may again be con- 
verted into litharge, and the gold will be 
left pure. This last operation is, in fact, 
a method of assaying sands which contain 
gold, rather than of obtaining it from them 
in the large way. 
Gold is also found in certain martial 
pyrites in Sweden and elsewhere; from 
which it may be extracted by forrefac'fion, 
or burning of the sulphur, and subsequent 
digestion in aqua-regia. 
To obtain gold in a state of purity, or to 
ascertain the quantity of alloy it may con- 
tain, it is exposed to a strong heat, together 
with lead, in a porous crucible. This opera- 
tion is called cupellation. 
After gold has passed the cupel, it may 
still contain either of the other perfect 
metals, platina or silver. The former is 
seldom suspected ; the latter is separated 
by the operations called quartation and 
parting. For all these operations see 
Assaying. ✓ 
The quantity of alloy is never considered 
as part of the value of metals which contain 
either gold or silver. In estimating or ex- 
pressing the fineness Gf gold, the whole 
mass spoken of is supposed to weigh 24 
carats of 12 grains each, either real or 
merely proportional, like the assayer’s 
weights ; and the pure gold is called fine. 
Thus, if gold be said to be 23 carats fine, it 
is to be understood that, in a mass weigh- 
ing 24 carats, the quantity of pure gold 
amounts to 23 carats. 
In such small works as cannot be assayed 
by scraping off a part, and cupelling it, the 
assayers endeavour to ascertain its quality 
or fineness by the touch. This is a method 
of comparing the colour and other proper- 
ties of a minute portion of the metal, with 
those of certain small bars whose composi- 
tion is known. These bars are called touch- 
needles; and they are rubbed upon the 
black basaltes, which, for that reason, is 
called the touch-stone. Black flint, or pot- 
tery, will serve the same purpose. Sets of 
golden needles may consist of pure gold ; 
pure gold twenty-three and a half carats 
with half a carat silver ; twenty-tiiree carats 
gold with one carat silver ; twenty- two and 
a half carats gold with one and a half carat 
silver, and so forth, till the silver amounts 
to four carats, after which the additions 
may proceed by whole carats. Other 
needles may be made in the same manner, 
with copper instead of silver ; and other 
sets may have the addition, consisting either 
of equal parts silver and copper, or such 
proportions as the occasions of business 
require. 
In foreign countries where trinkets and 
small works are required to be submitted to 
the assay of the touch, a variety of needles 
are necessary ; but they are not much used in 
England. They afford, however, a degree 
of information which is more considerable 
