Metals. M IN ERALOG V. Metals. 481 
beds and caverns tlie real gold-mine, while the Monti- 
cuii of Natakon itfelf is nothing more than an emanation 
.from the main body. In the year 1786, Mr. Gol berry 
carried on a fmall trade for gold at Galam; that which 
he received was made into ear-rings and other ornaments ; 
it was allayed at Paris in 1788, and it was, according to 
the account of the affayer, twenty-three carats fine. 
Gold is never found in any other than a native date; 
and is ufually alloyed with copper, or filver, or iron : 
fometimes with all of thefe. Native gold is feparated 
from the fubtonces accompanying it by means Amply 
mechanical, as pounding and walking; or by fulion with 
.lead; or by the procefs called amalgamation. Thefe 
proceffes are employed previoully to the operation of 
refinement. 
The procefs of wajhing , the principle of which has been 
already explained, is commonly employed in feparating 
gold from the land of rivers, See. 
The procefs by fufion with lead is applied principally 
to the ores of other metals, which contain a fufficient 
proportion of gold to repay the coll of extraction : thefe 
ores are, for the moll part, lulphurets of copper, See. but 
particularly fulphuret of iron, or iron pyrites: and are 
confequently called auriferous. Thefe lulphurets are 
roafted, or expoled to a fufficient degree of heat to expel 
moll of their fulphur ; which operation in a great mea- 
fure difengages the particles of gold before enveloped in 
the mafs; and then they are melted with lead. The lead 
combines with the gold, which is recovered by the pro¬ 
cefs of "refining. 
The procefs by amalgamation depends on the property 
which quickfilver polfelles of attracting and combining 
with gold ; and is applied either to auriferous metallic 
fulphurets,' or to native gold contained in indurated 
rocks. In either inftance the fubtonces containing the 
gold are ftamped and triturated with quickfilver, the ful¬ 
phurets however being previoully roalled; and during 
the procefs the quickfilver abforbs every particle of the 
gold, lofes proportionally its fluidity, and forms that kind 
of alloy which is called an amalgam: the term amalgam 
being applied inltead of alloy to a combination of any 
metal with quickfilver. This amalgam is afterwards 
walked by a current of water, in order to feparate the 
particles of earthy matter; and a great portion of the 
quickfilver is feparated from the gold by llraining it 
forcibly through linen bags : the gold which remains on 
the linen is then expofed to a degree of heat fufficient to 
volatilize every particle of the quickfilver; and the gold 
itfelf remains behind, alloyed however in general with 
filver, and fometimes other metals. 
The gold feparated by any of the three foregoing pro- 
ceffes is afterwards melted with the quantity of lead that 
has by experience been found neceffary, and is fubmitted 
to the procefs of euppcllation. This procefs is fo named 
from the veflej employed to hold the mixture of the lead 
and gold, called a coppel, or cuppel; it is made of cal¬ 
cined bones, which are powdered, and with the fmalleft 
quantity of water poffible formed into the appropriate 
fhape : the fubllance of this is very porous, and on that 
tireumftance in a great mealure depends its ufe. The 
ufe of the lead in the procefs of cuppellation depends 
partly on the property which it poffeiTes of being vitrified 
by the joint adtion of air and a high degree of heat; and 
partly on its power of promoting the vitrifadlion of almolt 
all the other metals, except gold or filver. The gold 
then, together with the lead, being placed on the cuppel, 
and a flrong heat being applied, together wdth a conftant 
current of atmoipherical air, the mafs is foon melted; 
and the lead, being vitrified by the joint adlion of the 
heat and air, and vitrifying the bale metals with which 
the native gold was alloyed, finks in the form of avifeid 
glafs into the fubftar.ee of the cuppel. For the effectual 
reparation of tin or iron, fulphuret of antimony is ufed 
after the lead. By a careful management of this procefs 
the lead and all the other metals are feparated, and the 
Vol. XV. No. 1059. 
mafs which remains behind confifts entirely of the gold, 
mixed with whatever proportion of filver was originally 
contained in it. If the reparation of the filver is req aired, 
the gold, after the completion of the foregoing procefs, 
is melted with three times its weight of filver; the mixed 
mafs when confolidated is flattened into laminae, and 
boiled in nitric acid ; which dilfolves the filver, and leaves 
the gold in a ftate of purity. See the article Chemistry, 
vol. iv. p.312. 
Profefl’or Schnaubert, of Mofcow, has lately made fcvc- 
ral attempts to feparate filver from gold by boiling the 
alloy in fulphuric acid ; this acid dilfolves the filver, 
and leayes the gold. The procefs, though by no means 
brought to a ftate of perfection, promifes at prefent to be 
attended with fuccefs. The great difference between the 
price of fulphuric acid and nitric acid, which is ufually 
employed for the purpofe, renders it defirable that this 
procefs, which originated with Mr. Keir, ihouid be fub- 
jeCted to farther trials. 
Gold forms alloys with the greater number of the me¬ 
tals, wdiich produce on the metal fo alloyed a very par¬ 
ticular change in its properties. An extenfive and accu¬ 
rate feries of experiments on thefe alloys w\as made by 
Mr. Hatchet, with the view of determining fome impor¬ 
tant and interefting faCts, relating to the ufe of gold as a 
coin. Thefe are detailed in the TranfaCtions of the Royal 
Society for the year 1803. The chief enquiry of Mr. 
Hatchet, as connected with the alloys of gold, was, whe¬ 
ther foft and duCtile gold, or gold made as hard as is 
compatible with the procefs of coining, fuffers moll by 
weqr. His experiments were intended to examine the 
eftefts which various metals produce upon gold, when 
combined with it in given proportions, beginning with 
•j^th, which is the ftandard proportion of alloy, and gra¬ 
dually decreafing to -rgW P art of mafs. The refults drawm 
from the trials were, that fine gold, alloyed with filver, 
with copper, and with tin, did not luffer any lofs during 
the experiment. The gold alloyed with lead only loll 
three grains, chiefly by vitrification; with iron it loft 
twelve grains, which formed fcoria; wdth bifmuth it loft 
twelve grains, chiefly by vitrification; with zink it loll a 
pennyweight by volatilization; and with arfenic it not 
only loft the whole quantity of alloy, but alfo two grains 
of the gold which were carried off in confequence of the 
rapid volatilization of the arfenic. Hence it was inferred, 
that only two metals are proper for the alloy of gold coin y 
namely, filver and copper; as all the others either confi- 
derably alter the colour or diminilh the duClility of gold. 
In refpeCl to the latter quality, the different alloys er- 
ployed in this feries of experiments appear to affeCl gold 
nearly in the following decreafing order: 1. bifmuth; 
2. lead; 3. antimony; 4. arfenic; 5. zink; 6. cobalt; 
7. manganefe; 8. nickel; 9. tin; 10. iron; n. platina. 
12. copper; and, 13. filver. The three firft haye nearly 
the fame effeCt on gold; and bifmuth is found to render 
gold brittle when the proportion of that metal is to gold 
only as 1 to 1920 ; even the vapour arifing from bifmuth, 
lead, and antimony, in fufion, produces thefe changes. 
The alloy with platina is of a yellowifh-white colour, 
very duCtile, and of a confiderable fpecific gravity. The 
alloy with filver in the ftandard proportion, or 1 to 12, 
approaches, as we have* feen above, the neareft to the 
duCtility of fine gold of any alloy; and its fpecific gravity 
differs but little from the mean Ipecific gravity of the 
two metals. In combination with copper, gold has its 
colour rather heightened than impaired; its hardnefs is 
increafed, and its duCtility very little leffened, when the 
ftandard proportion of 1 part in 12 is not exxeeded. This 
alloy of 22 carats fine forms the gold coin of the country. 
With quickfilver, gold unites with great facility, making 
with it an amalgam which will be deicribed hereafter. 
The alloy with iron is much harder than gold, very duc¬ 
tile and malleable; but the colour is debafed to a dullifh 
grey, inclining to white. Tin was formerly regarded as 
the metal which rendered the alloy with gold the moft 
6 G brittle. 
