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190
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DE NATURA FOSSILIUM
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ammoniac
has been dissolved. It is then placed in molten silver or one of the
metals or alloys mentioned above. If left in the molten metal for a
short time it becomes covered with it. Copper workers, in order to
avoid the expense of making sal ammoniac, cover the inside of copper
vases with pitch and pour the molten tin over them until they are covered. Similarly,
iron workers add tallow to the molten tin and then, after polishing
their object, coat it with the tin without rubbing it with vinegar and
sal ammoniac or coating part of it with pitch. Verdigris does not form
on brass that has been coated nor rust on iron. The advance of copper
and iron rust is checked by the metals with which the objects are
coated. This method of coating is not only seemly but very useful since
it prevents flaws and gives a more pleasing taste to liquids that are
placed in them. Enough concerning these things.
Artificial
metallic substances that do not have the appearance and form of metals
follow. These are made either within or outside furnaces. They form
within the furnaces when ore is smelted or when one metal is separated
from another or when copper is melted in a furnace and alloyed with
other metals. When metallic ores are smelted in the first furnace many
metallic substances are produced, namely, slag, stone, diphryges, cadmia, pompholyx, spodos, and flos aeris. When
one metal is parted from another in the second furnace whose large
shallow crucibles for separating the metals are called by our people foci6, litharge, plumbago, and spodos are the principal materials formed. When copper is alloyed or refined pompholyx and spodos are produced.
Metallic
substances are produced outside of furnaces from metals either mixed
with acid and finely powdered, producing verdigris, caeru-leum, or cerussa; or having been set on fire, producing ochra plumbaria, or minium; or driven to the top of a vessel, producing sublimate of mercury as the chemists call it, or sublimate of cadmia; or by a certain special process, producing cinnabaris. Finally some metallic substances may be hammered from metals such as scales of copper and iron.
Metallic
substances may be produced from other metallic substances either in
Nature, such as native minium, or artificially, such as artificial
minium, or by both methods, such as psoricum.
I shall treat first slag which the Greeks call σκωρία. It
is the excrement of metallic ore that has been refined in a furnace. It
separates from the molten metal as the latter flows from the furnace
into a crucible. The slag of silver, since it is usually drawn out into
long threads when it is removed from the crucible with hooks is called 'έλκυσμα by
the Greeks. The slag that is formed in smelters where copper is
separated from silver acts in this same fashion. Slag forms from ores
of gold, silver, copper, tin, lead, and iron but not from ores of
quicksilver and bismuth since these ores are not smelted because of the
ease with which the metals can be extracted
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5 From the word for hearth.
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