The Artist's Assistant, In the Study and Practice of Mechanical Sciences: Calculated for the Improvement of Genius. Illustrated with Copper-Plates (Birmingham, [ca. 1785])

284 THE ARTIST'S ASSISTANT.

true oil which congeals itfelf no longer, and thig
Will procure vou what,is called the fix-balm.

Next to that operation, you will make an aquafortis
with equal par's of faltpetre, dried vitriol, and roch-
alum ; and before you put the receiver to the cucur-
bit, add tleel filings, antimony, verdigrife, in fubtile
powder, tutty and cinnabar, of each half an ouncce,
or one ounce, according to the quantity of aquafortis
you wan' to draw. Cohobatc the fpirits feven times
over, upon the fasces, which you will grind each
time on a marble table.

Diffolve one ounce of filver in three of this liquor ;
and, on that folution, ftill, drop by drop, one ounce
of your nitre-oil, in a bottle made like the hour-
glafles, which, after the operation rauft be at moil
only half full, and which you will cover with an-
other inverted, fo that the neck of the under one
fhould get into that of the upper one. Or elfe, put
it in a matrafs with a long neck, which you will feal
hermetic?.!ly ; but, if you make ufe of bottles, take
care to lure the joints ; place this over hot afhes, and
plunge it in them to the heigth of fix inches. Give
under this a lamp fire, which fhould not reach
the matter by three fingers diftance. You will get
every dav to the amount of a filver pennyweight of
filver fixed into gold ; and when the whole fhall
have been fixed thus, day after day, the aquafortis,
which before was green as an emerald, will become
as clear as pump-water. Let the competition cool,
and divide the water from the oil, which will never
be the worfe for ufe, and muft therefore be preferved.
At the bottom of the veffel you will find the filver
fixed into gold.

Permutation