into cakes. The glass extracted from the crucible is ground to powder, and
to this are added litharge, argol, glass-galls, and saltpetre, and they are
melted in an earthen crucible. The button that settles is transferred to the
cupel and re-melted.
If the silver was not sufficiently dried by the heat of the fire, that which
is contained in the upper part of the ampulla will appear black ; this when
melted will be consumed. When the lute, which was smeared round the
lower part of the ampulla, has been removed, it is placed in the crucible and
is re-melted, until at last there is no more appearance of black13.
If to the first aqua the other which contains silver is to be added, it
must be poured in before the powerful vapours appear, and the aqua gives off
the oily substance, and the operculum becomes red ; for he who pours in the
aqua after the vapour appears causes a loss, because the aqua generally spurts
out and the glass breaks. If the ampulla breaks when the gold is being parted
from the silver or the silver from the aqua, the aqua will be absorbed by the
sand or the lute or the bricks, whereupon, without any delay, the red hot coals
should be taken out of the furnace and the fire extinguished. The sand and
bricks after being crushed should be thrown into a copper vessel, warm water
should be poured over them, and they should be put aside for the space of
twelve hours ; afterward the water should be strained through a canvas, and
the canvas, since it contains silver, should be dried by the heat of the sun or
the fire, and then placed in an earthen crucible and heated until the silver
melts, this being poured out into an iron mould. The strained water should
be poured into an ampulla and separated from the silver, of which it contains
a minute portion ; the sand should be mixed with litharge, glass-galls,
argol, saltpetre, and salt, and heated in an earthen crucible. The button
which settles at the bottom should be transferred to a cupel, and should
be re-melted, in order that the lead may be separated from the silver. The
lute, with lead added, should be heated in an earthen crucible, then
re-melted in a cupel.
We also separate silver from gold by the same method when we assay
them. For this purpose the alloy is first rubbed against a touchstone, in
order to learn what proportion of silver there is in it ; then as much silver
as is necessary is added to the argentiferous gold, in a bes of which there
must be less than a semi-uncia or a semi-uncia and a sicilicus1* of copper.
After lead has been added, it is melted in a cupel until the lead and the
copper have exhaled, then the alloy of gold with silver is flattened out, and
little tubes are made of the leaves ; these are put into a glass ampulla,
and strong aqua is poured over them two or three times. The tubes after
this are absolutely pure, with the exception of only a quarter of a siliqua,
which is silver ; for only this much silver remains in eight unciae of gold15.
wWe do not understand this " appearance of black." If the nitrate came into contact
with organic matter it would, of course, turn black by reduction of the silver, and sunlight
would have the same effect.
14This would be equal to from 62 to 94 parts of copper in 1,000.
lsAs 144 siliquae are 1 uncia, then £ siliqua in 8 unciae would equal one part silver in
4,608 parts gold, or about 999.8 fine.
