in which the air is drawn in through holes ; or else they are placed in a goldsmith's forge.
Just as aqua valens poured over silver, from which the sulphur has
parted the gold, shows us whether all has been separated or whether
particles of gold remain in the silver ; so do certain ingredients, if placed in
the pot or crucible " alternately " with the gold, from which the silver has
been parted by stibium, and heated, show us whether all have been
separated or not.
We use cements18 when, without stibium, we part silver or copper or both
so ingeniously and admirably from gold. There are various cements. Some
18As will be shown in the historical note, this process of separating gold and silver
is of great antiquity—in all probability the only process known prior to the Middle Ages, and
in any event, the first one used. In general the process was performed by " cementing "
the disintegrated bullion with a paste and subjecting the mass to long-continued heat at a
temperature under the melting point of the bullion. The cement (comfiositio) is of two
different species ; in the first species saltpetre and vitriol and some aluminous or silicious
medium are the essential ingredients, and through them the silver is converted into nitrate
and absorbed by the mass ; in the second species, common salt and the same sort of medium
are the essentials, and in this case the silver is converted into a chloride. Agricola does not
distinguish between these two species, for, as shown by the text, his ingredients are badly
mixed.
