1are equal portions of very minute lead granules,
melted salt, stíbíum and
iron slag Or else take equal portions of gold ore, vitriol, argol, and of salt.
So much for the fluxes.
iron slag Or else take equal portions of gold ore, vitriol, argol, and of salt.
So much for the fluxes.
In the assay furnace, when it has been prepared in the way in which I
have described, is first placed a muffle. Then selected pieces of live charcoals
are laid on it, for, from pieces of inferior quality, a great quantity of ash collects
around the muffle and hinders the action of the fire. Then the scorifiers are
placed under the muffle with tongs, and glowing coals are placed under the
fore part of the muffle to warm the scorifiers more quickly; and when the lead
or ore is to be placed in the scorifiers, they are taken out again with the
tongs. When the scorifiers glow in the heat, first of all the ash or small
charcoals, if any have fallen into them, should be blown away with an iron
pipe two feet long and a digit in diameter; this same thing must be done
if ash or small coal has fallen into the cupels. Next, put in a small ball of lead
with the tongs, and when this lead has begun to be turned into fumes and
consumed, add to it the prepared ore wrapped in paper. It is preferable that
the assayer should wrap it in paper, and in this way put it in the scorifier,
than that he should drop it in with a copper ladle; for when the
scorifiers are small, if he uses a ladle he frequently spills some part of the
ore. When the paper is burnt, he stirs the ore with a small charcoal held in
the tongs, so that the lead may absorb the metal which is mixed in the ore;
when this mixture has taken place, the slag partly adheres by its cir
cumference to the scorifier and makes a kind of black ring, and partly
floats on the lead in which is mixed the gold or silver; then the slag must
be removed from it.
have described, is first placed a muffle. Then selected pieces of live charcoals
are laid on it, for, from pieces of inferior quality, a great quantity of ash collects
around the muffle and hinders the action of the fire. Then the scorifiers are
placed under the muffle with tongs, and glowing coals are placed under the
fore part of the muffle to warm the scorifiers more quickly; and when the lead
or ore is to be placed in the scorifiers, they are taken out again with the
tongs. When the scorifiers glow in the heat, first of all the ash or small
charcoals, if any have fallen into them, should be blown away with an iron
pipe two feet long and a digit in diameter; this same thing must be done
if ash or small coal has fallen into the cupels. Next, put in a small ball of lead
with the tongs, and when this lead has begun to be turned into fumes and
consumed, add to it the prepared ore wrapped in paper. It is preferable that
the assayer should wrap it in paper, and in this way put it in the scorifier,
than that he should drop it in with a copper ladle; for when the
scorifiers are small, if he uses a ladle he frequently spills some part of the
ore. When the paper is burnt, he stirs the ore with a small charcoal held in
the tongs, so that the lead may absorb the metal which is mixed in the ore;
when this mixture has taken place, the slag partly adheres by its cir
cumference to the scorifier and makes a kind of black ring, and partly
floats on the lead in which is mixed the gold or silver; then the slag must
be removed from it.
The lead used must be entirely free from every trace of silver, as is that
which is known as Víllacense.26 But if this kind is not obtainable, the lead
must be assayed separately, to determine with certainty that proportion of
silver it contains, so that it may be deducted from the calculation of the
ore, and the result be exact; for unless such lead be used, the assay will be
false and misleading. The lead balls are made with a pair of iron tongs,
about one foot long; its iron claws are so formed that when pressed
together they are egg-shaped; each claw contains a hollow cup, and when
the claws are closed there extends upward from the cup a passage, so there
are two openings, one of which leads to each hollow cup. And so when the
molten lead is poured in through the openings, it flows down into the hollow
cup, and two balls are formed by one pouring.
which is known as Víllacense.26 But if this kind is not obtainable, the lead
must be assayed separately, to determine with certainty that proportion of
silver it contains, so that it may be deducted from the calculation of the
ore, and the result be exact; for unless such lead be used, the assay will be
false and misleading. The lead balls are made with a pair of iron tongs,
about one foot long; its iron claws are so formed that when pressed
together they are egg-shaped; each claw contains a hollow cup, and when
the claws are closed there extends upward from the cup a passage, so there
are two openings, one of which leads to each hollow cup. And so when the
molten lead is poured in through the openings, it flows down into the hollow
cup, and two balls are formed by one pouring.
In this place I ought not to omit mention of another method of assaying
employed by some assayers. They first of all place prepared ore in the
scorifiers and heat it, and afterward they add the lead. Of this method I
cannot approve, for in this way the ore frequently becomes cemented, and
for this reason it does not stir easily afterward, and is very slow in mixing
with the lead.
employed by some assayers. They first of all place prepared ore in the
scorifiers and heat it, and afterward they add the lead. Of this method I
cannot approve, for in this way the ore frequently becomes cemented, and
for this reason it does not stir easily afterward, and is very slow in mixing
with the lead.