1of this powder there are mixed two unciae of yellow litharge, likewise crushed.
This mixture is put into a scorifier large enough to hold it, and placed under
the muffle of a hot furnace; when the charge flows like water, which occurs
after half an hour, it is taken out of the furnace and poured on to a stone,
and when it has hardened it has the appearance of glass, and this is likewise
crushed. This powder is sprinkled over any metalliferous ore which does
not easily melt when we are assaying it, and it causes the slag to exude.
This mixture is put into a scorifier large enough to hold it, and placed under
the muffle of a hot furnace; when the charge flows like water, which occurs
after half an hour, it is taken out of the furnace and poured on to a stone,
and when it has hardened it has the appearance of glass, and this is likewise
crushed. This powder is sprinkled over any metalliferous ore which does
not easily melt when we are assaying it, and it causes the slag to exude.
Others, in place of litharge, substitute lead ash,22 which is made in the
following way: sulphur is thrown into lead which has been melted in a
crucible, and it soon becomes covered with a sort of scum; when this is
removed, sulphur is again thrown in, and the skin which forms is again taken
off; this is frequently repeated, in fact until all the lead is turned into
powder. There is a powerful flux compound which is made from one uncía
each of prepared saltpetre, melted salt, glass-gall, and argol, and one-third
of an uncia of litharge and a bes of glass ground to powder; this flux, being
added to an equal weight of ore, liquefies it. A more powerful flux is made by
placing together in a pot, smeared on the inside with litharge, equal portions
of white argol, common salt, and prepared saltpetre, and these are heated
until a white powder is obtained from them, and this is mixed with as much
litharge; one part of this compound is mixed with two parts of the ore which
is to be assayed. A still more powerful flux than this is made out of ashes
of black lead, saltpetre, orpiment, stíbíum, and dried lees of the aqua with
which gold workers separate gold from silver. The ashes of lead23 are made from
one pound of lead and one pound of sulphur; the lead is flattened out into
sheets by pounding with a hammer, and placed alternately with sulphur in a
crucible or pot, and they are heated together until the fire consumes the
sulphur and the lead turns to ashes. One líbra of crushed saltpetre is mixed
with one libra of orpiment similarly ground to powder, and the two are cooked
in an iron pan until they liquefy; they are then poured out, and after cool
ing are again ground to powder. A líbra of stíbíum and a bes of the
dried lees (of what?) are placed alternately in a crucible and heated to the
point at which they form a button, which is similarly reduced to powder.
A bes of this powder and one líbra of the ashes of lead, as well as a líbra of
powder made out of the saltpetre and orpiment, are mixed together and a
following way: sulphur is thrown into lead which has been melted in a
crucible, and it soon becomes covered with a sort of scum; when this is
removed, sulphur is again thrown in, and the skin which forms is again taken
off; this is frequently repeated, in fact until all the lead is turned into
powder. There is a powerful flux compound which is made from one uncía
each of prepared saltpetre, melted salt, glass-gall, and argol, and one-third
of an uncia of litharge and a bes of glass ground to powder; this flux, being
added to an equal weight of ore, liquefies it. A more powerful flux is made by
placing together in a pot, smeared on the inside with litharge, equal portions
of white argol, common salt, and prepared saltpetre, and these are heated
until a white powder is obtained from them, and this is mixed with as much
litharge; one part of this compound is mixed with two parts of the ore which
is to be assayed. A still more powerful flux than this is made out of ashes
of black lead, saltpetre, orpiment, stíbíum, and dried lees of the aqua with
which gold workers separate gold from silver. The ashes of lead23 are made from
one pound of lead and one pound of sulphur; the lead is flattened out into
sheets by pounding with a hammer, and placed alternately with sulphur in a
crucible or pot, and they are heated together until the fire consumes the
sulphur and the lead turns to ashes. One líbra of crushed saltpetre is mixed
with one libra of orpiment similarly ground to powder, and the two are cooked
in an iron pan until they liquefy; they are then poured out, and after cool
ing are again ground to powder. A líbra of stíbíum and a bes of the
dried lees (of what?) are placed alternately in a crucible and heated to the
point at which they form a button, which is similarly reduced to powder.
A bes of this powder and one líbra of the ashes of lead, as well as a líbra of
powder made out of the saltpetre and orpiment, are mixed together and a