1is first
roasted in a hot fire for about six or eight hours; next, when it has
cooled, it is crushed and washed; then the concentrates made by washing
are again roasted, crushed, washed, dried, and weighed. The portion which
it has lost whilst it is being roasted and washed is taken into account, and
these concentrates by washing represent the cake which will be melted out
of the copper ore. Place three centumpondia (lesser weights) of this, mixed
with three centumpondia (lesser weights) each of copper scales30, saltpetre,
and Venetian glass, mixed, into the triangular crucible, and place it in the iron
hoop which is set on the hearth in front of the double bellows. Cover the crucible
with charcoal in such a way that nothing may fall into the ore which is to be
melted, and so that it may melt more quickly. At first blow a gentle blast with
the bellows in order that the ore may be heated gradually in the fire; then
blow strongly till it melts, and the fire consumes that which has been added to
it, and the ore itself exudes whatever slag it possesses. Next, cool
the crucible which has been taken out, and when this is broken you will find
the copper; weigh this, in order to ascertain how great a portion of the ore
the fire has consumed. Some ore is only once roasted, crushed, and washed;
and of this kind of concentrates, three centumpondia (lesser weights) are
taken with one centumpondíum each of common salt, argol and glass
galls. Heat them in the triangular crucible, and when the mixture has
cooled a button of pure copper will be found, if the ore is rich in this metal.
If, however, it is less rich, a stony lump results, with which the copper is
intermixed; this lump is again roasted, crushed, and, after adding stones
which easily melt and saltpetre, it is again melted in another crucible, and
there settles in the bottom of the crucible a button of pure copper. If you
wish to know what proportion of silver is in this copper button, melt it in a
cupel after adding lead. With regard to this test I will speak later.
cooled, it is crushed and washed; then the concentrates made by washing
are again roasted, crushed, washed, dried, and weighed. The portion which
it has lost whilst it is being roasted and washed is taken into account, and
these concentrates by washing represent the cake which will be melted out
of the copper ore. Place three centumpondia (lesser weights) of this, mixed
with three centumpondia (lesser weights) each of copper scales30, saltpetre,
and Venetian glass, mixed, into the triangular crucible, and place it in the iron
hoop which is set on the hearth in front of the double bellows. Cover the crucible
with charcoal in such a way that nothing may fall into the ore which is to be
melted, and so that it may melt more quickly. At first blow a gentle blast with
the bellows in order that the ore may be heated gradually in the fire; then
blow strongly till it melts, and the fire consumes that which has been added to
it, and the ore itself exudes whatever slag it possesses. Next, cool
the crucible which has been taken out, and when this is broken you will find
the copper; weigh this, in order to ascertain how great a portion of the ore
the fire has consumed. Some ore is only once roasted, crushed, and washed;
and of this kind of concentrates, three centumpondia (lesser weights) are
taken with one centumpondíum each of common salt, argol and glass
galls. Heat them in the triangular crucible, and when the mixture has
cooled a button of pure copper will be found, if the ore is rich in this metal.
If, however, it is less rich, a stony lump results, with which the copper is
intermixed; this lump is again roasted, crushed, and, after adding stones
which easily melt and saltpetre, it is again melted in another crucible, and
there settles in the bottom of the crucible a button of pure copper. If you
wish to know what proportion of silver is in this copper button, melt it in a
cupel after adding lead. With regard to this test I will speak later.
Those who wish to know quickly what portion of silver the copper ore
contains, roast the ore, crush and wash it, then mix a little yellow litharge
with one centumpondium (lesser weights) of the concentrates, and put the
mixture into a scorifier, which they place under the muffle in a hot furnace for
the space of half an hour. When the slag exudes, by reason of the melting force
which is in the litharge, they take the scorifier out; when it has cooled, they
cleanse it of slag and again crush it, and with one centumpondíum of it they
mix one and a half uncíae of lead granules. They then put it into another
scorifier, which they place under the muffle in a hot furnace, adding to the
mixture a little of the powder of some one of the fluxes which cause ore to
melt; when it has melted they take it out, and after it has cooled, cleanse
it of slag; lastly, they heat it in the cupel till it has exhaled all of the lead,
and only silver remains.
contains, roast the ore, crush and wash it, then mix a little yellow litharge
with one centumpondium (lesser weights) of the concentrates, and put the
mixture into a scorifier, which they place under the muffle in a hot furnace for
the space of half an hour. When the slag exudes, by reason of the melting force
which is in the litharge, they take the scorifier out; when it has cooled, they
cleanse it of slag and again crush it, and with one centumpondíum of it they
mix one and a half uncíae of lead granules. They then put it into another
scorifier, which they place under the muffle in a hot furnace, adding to the
mixture a little of the powder of some one of the fluxes which cause ore to
melt; when it has melted they take it out, and after it has cooled, cleanse
it of slag; lastly, they heat it in the cupel till it has exhaled all of the lead,
and only silver remains.
Lead ore may be assayed by this method: crush half an uncía of
pure lead-stone and the same quantity of the chrysocolla which they call
borax, mix them together, place them in a crucible, and put a glowing coal
pure lead-stone and the same quantity of the chrysocolla which they call
borax, mix them together, place them in a crucible, and put a glowing coal
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