C H E M I 
Tufficient to gild a filver wire of 4.44 leagues in length,- 
and it is reduced into plates lufficiently thin tq be blown 
away by the leaft breath of wind. A grain of gold, ac¬ 
cording to the calculation of Lewis, is capable of co¬ 
vering the furface of more than 1400 fquare inches. It 
is the molt tenacious of all the metals; a gold wire ot 
one tenth of an inch in diameter, being capable of ful- 
taining a weight of 500 pounds without breaking. Gold 
loon becomes hard under the hammer, but immediately 
recovers its duftility by ignition. The colour of gold is 
fulceptible of coniiderable variety; it is more oriels yel¬ 
low, and fome fpecimens are almoft white ; theie differ¬ 
ences howeverfeem to depend on fome alloy. Gold has 
neither fmell nor talle; it is capable of cryftallizing by 
cooling, in Ihort quadrangular pyramids, as Tillet and 
Mongez have obferved. 
Gold is almoft always found in a native or virgin ftate : 
it is fometimes met with in fmall infulated malfes, dil- 
poled on a matrix of quartz; fometimes it is in fmall 
fpangles, intermixed with fand at the bottom of \vaters; 
and laftly, it is obtained from many ores into the com- 
pofition of which it enters, fuch as galena, blend, red 
filver ore, and virgin filver. It is almoft always united 
with a certain quantity of filver and other metals, form¬ 
ing natural alloys. 
Gold expoied to the fire becomes red before it 
melts. In a ftrong heat it appears of a brilliant fea- 
green colour; but it does not melt completely till heated 
to whitenefs, and cryftallizes by flow cooling. The 
ftrongeft heat of a furnace continued for an indefinite 
time does not produce any change in this metal; 
Kunckel and Bo)de made this experiment, by expofing 
gold for feveral months to the fire of a glal's-houfe. This 
inalterability, however, is merely relative to the fires we 
are able to make with combuftible fubftances ; for it ap¬ 
pears certain that a ftronger heat, fuch as that of the fun 
concentrated by glafs lenfes, is capable of depriving it 
of its metallic properties. Homberg obferved that this 
metal, when expoied to the focus of the lens of Tfchirn- 
haufen, fumed, was volatilized, and even vitrified. 
Macquer found, that gold expoied to the focus of the 
lens of Trudaine, melted and exhaled a fume which 
gilded filver, and was therefore gold in a volatile ftate ; 
that the globule of melted gold was agitated with a ra¬ 
pid circular motion, and became covered with a dull, 
and, as it were, earthy, pellicle; and, laftly, that a vio¬ 
let vitrification was formed on the middle of the globule. 
This vitrification gradually extended, and produced a 
kind of button, flatter, or of a larger curvature, than 
that of the globule of gold, which ltuck on the globule 
itfelf, as the tranfparent cornea appears on the fclerotica - 
of the eye. This glafs increaled in fize, while the gold 
itfelf continually diminifhed; the fupport always ap¬ 
peared tinged with a purple colour, apparently pro¬ 
duced by the abforption of part of the glafs. Time did 
not permit Macquer to vitrify entirely a certain quantity 
of gold. This celebrated chemift obferves, that it is a 
neceffary condition, that the violet glafs fhould be re¬ 
duced with combuftible matters, in order to juftify the 
alfertion, that it is the oxycl of that perfe£t metal, which 
would evidently appear to be the cafe, if it became re¬ 
vived into. gold. However this may be, we think itmay 
be confidered as a true vitrified oxyd of gold, with lo 
much the greater probability, as, in many operations 
with this metal, the purple colour is conftantiy produced, 
and many preparations of gold are employed to give that 
colour to enamel and porcelain. Gold is therefore oxy- 
difiable like the other metals, and only requires, as like- 
wife does liiver, a ftronger heat, and a longer time, to 
unite with the bale or" ail;, than other metallic fub¬ 
ftances. Thefe circurnftances, no doubt, bear relation 
to its denfity, and its fmall tendency to unite with oxy¬ 
gen. Gold may be converted into the ftate of purple 
oxyd by the ad'tion of a ftrong electric fpark. Gold is 
not changed by expofure to air; its furface becomes tar- 
Vol. IV. No. 199. 
S T R Y. 313 
nifhed merely by the depofition of foreign bodies which 
continually float in the atmofphere. Water does not at 
all change it, though, according to the experiments of 
Lagaraye, it feems capable of dividing it. 
To prepare phofphorated gold, mix one half part of 
parted gold in powder, ( with one part of phofphoric glafs, 
and about one-eighth of charcoal: put the whole into a 
crucible, covering the mixture with a little powdered 
charcoal: then urge a violent, heat, ftrong enough to 
melt the gold: much phofphoric vapour flies off during 
the operation', but a little of the phofphorus remains 
combined with the gold. The gold is collected at the 
bottom of the crucible, but not in its natural ftate ; it 
is whiter, breaks under the hammer, and has a cryftal- 
line form. Care mult be taken not to continue the fire 
too long, as in that cafe the gold will be found unchang¬ 
ed at the bottom of the crucible ; for Pelletier fays, the 
combination may be decompofed, by roalting it in an 
open fire. 
Sulphur and gold, when both very pure, will not com¬ 
bine; but an addition of iron makes them unite: this 
explains the prefence of gold in pyrites. Sulphur is ad- 
vantageoufly ufed to. feparate metals, with which gold 
may be alloyed, more elpecially filver: this alloy is melt¬ 
ed in a crucible, and flowers of fulphur, or fulphur in 
powder, is thrown on its furface : the latter fubftance, 
melting and combining with the filver, floats above the 
gold in the form of a blackifh fcoria. It mull be ob- 
lerved, that this operation, called dry parting, never le- 
parates the two metals accurately from each other, and 
that it is not ufed, except when the mafs of filver does 
not contain a fuflicient quantity of gold to repay the 
expence of the operation of parting by aquafortis. 
Alkaline lulphures completely diffolve gold. Stahl 
even thinks that this procefs was ufed by Moles, to ren¬ 
der the calf of gold adored by the Ifraelites foluble in wa¬ 
ter : to form this combination, a mixture of equal parts 
of fulphur and potalh mull be quickly fufed with one- 
eighth part of the whole weight of leaf gold; this mat¬ 
ter being poured out, and levigated on a ftone, forms, 
with hot diftilled water, a yellowilh green folution, con¬ 
taining an auriferous lirlphure of potalh ; the metal may 
be precipitated by means of acids, and fcparated from 
the Iulphur, which falls down at the lame time, by heat¬ 
ing it in an open veflel. 
Gold combines with mod metallic fubftances, and ex¬ 
hibits many important phenomena in its combinations. 
It unites with arlenic, and forms a brittle pale com-' 
pound ; the laft portions of arfenic are very difficultly, 
ieparated from this alloy by the aflion of heat; the gold 
feems to communicate fixity to it. The alloy of cobalt 
and manganefe with gold has not been lufficiently exa¬ 
mined. It unites with bifmuth, which renders it white 
and brittle, as do likewife nickel and antimony; as thefe 
metals are very oxydifiable, and, for the molt part, fu- 
fible, they are ealily Ieparated from gold by the combined 
aftion of lire and air. 
Sulphure of antimony has been greatly extolled by the 
alchemifts for the purification of gold; when this fub¬ 
ftance is melted with half its weight of gold, alloyed 
with other metallic fubftances, as copper, iron, or filver, 
the fulphur of the antimony unites to the alloy, and fe- 
parates them from the gold, which is found at the bottom of 
the veflel; this gold is contaminated with antimony, and 
mult be purified, by a white beat; the antimony by this 
treatment is volatilized, but the laft portions require a 
very ftrong heat to drive them off. It is likewife obferv¬ 
ed, that this metal carries up certain portions of gold in 
its volatilization. This procefs, fo celebrated by the al¬ 
chemifts, has not, therefore, any advantage over that in 
which fulphur is employed alone. 
Gold readily unites with zink ; the produft is a mixed 
metal, more brittle and white in proportion as. the'quan¬ 
tity of metal is greater- This alloy, made with equal 
parts of each metal, is of a very fine grain, and takes i» 
4L beau- 
