as
I have said, and from iron by blows of a hammer. Although Dioscorides
says this scale has the same properties as copper scale, the iron scale
is more astringent and that from steel even more so. For this reason
the latter is very useful in treating malignant ulcers. Copper scale
is more acrid and, therefore, purges and eats away the flesh more than
iron scale and is more efficacious in purging the stomach. But this is
enough concerning the products of the first furnace and the scale of
copper, iron, and steel.
I shall now take up the products of the second furnace, namely foam of silver (spuma argenti) and plumbago. The
Greeks call foam of silver λιθάργυρο?, that is, stone of silver. The
Greeks regarded it as a natural substance while the Latins believed it
occurred in Nature in an impure form. It is more correct to call it
foam or stone of lead since it is produced from lead and lead from it
and it is not produced from silver nor silver from it. If foam is
produced from a mixture of lead and silver when they are being parted
we know that it comes from the lead and not from the silver since none
of the silver is lost and all of the lead is changed into foam and plumbago.
Foam is produced in many ways. First, from plumbaria arena,7 second from galena (plumbarius lapis), and
third from sheets of lead. All are heated in shallow crucibles until
they are completely changed, partly into foam, partly into plumbago.9 A
fourth method uses mixtures of lead and silver; a fifth, mixtures of
gold and lead; a sixth, using mixtures of gold, silver, and lead. In
the last three methods gold, silver, or a gold-silver alloy are left
while all the lead is converted into foam or lead oxide. When copper is
added to a mixture that contains silver, as is a common practice, it
increases the amount of silver in the lead but the copper, together
with the lead is converted into foam and plumbago.9
Foam varies in color. It is either dark yellow or white. The dark yellow variety is called chrysitis because it resembles gold while the white variety that resembles silver is called argyritis. I realize that Pliny knew of another one. Chrysitis is better than argyritis. It has been subjected to a hotter fire that has produced the color.10
Foam differs in degree of consolidation since it may be either solid or distended. The Greeks call the former stereotis since it has congealed in a solid mass, and the latter pneumenis when
it has congealed in tubular masses. If foam flows down into the lower
crucible from the upper and is then left for a long time the mass
becomes heavier but if it is taken from the crucible immediately and
rolled about in a fine mesh fish-net it will form tubular masses of
moderate weight.
7 Literally, lead sand, probably the fines resulting from hand picking lead ores.
* Agricola and other writers include a number of materials under plumbago. Here he refers to the lead oxide litharge (yellow) and other oxides.
' Actually this practice, in effect, debased the silver.
10 The white oxide is the basic lead carbonate; the yellow oxide is massicot or litharge.
