ASSAYING. 
used is tliree pai ts to one of the gold, from 
whence the process obtained the name of 
quartation. Several good assayers think 
two parts oF silver are sufficient. More 
than three parts also may be used, but then 
it will protract the process needlessly. 
Though when copper also as well as silver 
is present, the parting may be proceeded to, 
as this metal is likewise soluble in aqua- 
fortis ; yet it is found to have some advant- 
ages to cupel the mixture first with lead ; 
and likewise even when no copper is com- 
bined with the gold. 
The cupellation of gold is thus conduct- 
ed ; the portion of the alloy of silver being 
estimated by touch-needles, as much sil- 
ver is added as will make the entire quan- 
tity of this metal about thrice the weight of 
pure gold. 
The proportion of lead to the alloy of 
copper or other base metal, is nearly the 
same as for silver, which will be shewn par- 
ticularly in the annexed table. The heat 
necessary in the process is greater than for 
silver, and may he used with freedom, as 
none of the gold is lost by volatilization. 
The lighting of' the fused globule of gold 
takes place as in silver. The button is cool- 
ed, taken out and weighed, then hammered 
fiat and annealed, and afterwards laminated 
between steel roller': to a thin plate about 
the substance of a wafer, again heated to 
redness, and then coiled up into a spiral 
roll. The button of gold when it lightens 
still retains a minute portion of lead ; this 
may be got rid of by its being kept a little 
time in fusion in a clean vessel. The lead 
entirely disappears after parting. 
The spiral roll is called a cornet, and 
when prepared is put into a glass matrass, 
shaped like a pear, in order to part the sil- 
ver from it, and about thrice its weight of 
pure nitric acid poured on it moderately di- 
luted (so as to be about 1.25 specific gravity)’. 
The glass is set on a sand bath, or over char- 
coal to boil. When warm the acid dissolves 
the silver; as lonyas it continues to act, the 
corpet is studded with minute bubbles ; 
when these discontinue, or are united in 
one large one, it is a sign that the acid has 
ceased to operate. About twenty minutes 
are required for tins process. 
The cornet is now corroded throughout, 
having lost its silver; it retains the same 
form, but is very slender and brittle. It is 
of importance to the accuracy of the assay 
that it should not be broken. The hot acid 
solution ofsilver is then poured off with great 
care, and fresh aeid rather stronger is add- 
ed to clear away all remains of the silver, 
and boiled as before, but only for five or 
six minutes. It is then decanted and added 
to the first solution, and the parting glass is 
filled with hot distilled water, to wash off 
all remains of the solution. A small cruci- 
ble is to be inverted over the glass while it 
is full of water, the latter is then nimbly 
turned, and the cornet falls gently into the 
crucible through the water ; which beinrr 
poured off, the crucible is dried and heated 
to redness under a muffle, when the cornet 
shrinks extremely in every direction, be- 
comes firm, and when cooled regains its 
metallic -lustre, and is soft and flexible. It 
is then most accurately weighed and the 
process is finished. 
The final weight of the gpld cornet indi- 
cates the absolute quantity of this metal in the 
assayed sample. The difference between the 
weight of the button after cupellation (de- 
ducting the silver added) and the first sam- 
ple, is the weight of the copper, or other 
base metal in the gold ; and the difference 
between the gold cornet, together with the 
silver added, and the button after cupella- 
tion, is the quantity of silver with which the 
gold was alloyed. 
The silver is usually recovered from the 
solution left after parting, by immersing in 
it plates of bright copper, which dissolve 
and precipitate the silver in its metallic 
form. 
Touch-needles for gold are formed in the 
same manner as for silver, but more of them 
are required, as the various combinations 
of three metals are to be examined by them 
in this case. Four sets of them are usually 
employed ; one in which pure silver is used 
for the alloy, another in which the alloy is 
two parts silver and one of copper, a third 
with two parts copper and one of silver, and 
a fourth of copper only. In trials with these 
needles nitric acid is of singular service, a 
drop of it is let fall on the streak of metal 
on the touch-stone ; in eight or ten seconds 
it is washed off and the effect observed. If 
the streak preserves its golden brilliance 
unaltered, the metal is judged to be of a 
certain degree of fineness. If it looks red, 
dull, and coppery, it is less fine ; but if the 
streak is almost entirely effaced, it contains 
very little gold. 
A peculiar set of weights are used for 
assaying. 
The quantity of metal taken for an assay 
is always very small ; in this country gene- 
rally hom 18 to 36 grains troy for silver, 
and from 6 to 12 grains for gold. Tins is 
