As great expense is incurred in parting the metals by the methods that
I have explained, as night vigils are necessary when aqua vahns is made,
and as generally much labour and great pains have to be expended on this
matter, other methods for parting have been invented by clever men, which
are less costly, less laborious, and in which there is less loss if through carelessness an error is made. There are three methods, the first performed with
sulphur, the second with antimony, the third by means of some compound
which consists of these or other ingredients.
In the first method,16 the silver containing some gold is melted in a
crucible and made into granules. For every libra of granules, there is taken
a sixth of a libra and a sicilicus of sulphur (not exposed to the fire) ; this,
when crushed, is sprinkled over the moistened granules, and then they are put
into a new earthen pot of the capacity of four sextarn, or into several of them
if there is an abundance of granules. The pot, having been filled, is covered
with an earthen lid and smeared over, and placed within a circle of fire set one
and a half feet distant from the pot on all sides, in order that the sulphur
added to the silver should not be distilled when melted. The pot is opened,
leThe object of this treatment with sulphur and copper is to separate a considerable
portion of silver from low-grade bullion {i.e., silver containing some gold), in preparation
for final treatment of the richer gold-silver alloy with nitric acid. Silver sulphide is created
by adding sulphur, and is drawn off in a silver-copper regulus. After the first sentence, the
author uses silver alone where he obviously means silver " containing some gold," and further
he speaks of the " gold lump " (massula) where he likewise means a button containing a great
deal of silver. For clarity we introduced the term " regulus " for the Latin mistura. The
operation falls into six stages : a, granulation ; b, sulphurization of the granulated bullion ;
c, melting to form a combination of the silver sulphide with copper into a regulus, an alloy
of gold and silver settling out ; d, repetition of the treatment to abstract further silver from
the " lump ; " e, refining the " lump " with nitric acid ; /, recovery of the silver from the
regulus by addition of lead, liquation and cupellation.i
The use of a " circle of fire " secures a low temperature that would neither volatilize
the sulphur nor melt the bullion. The amount of sulphur given is equal to a ratio of 48 parts
bullion and 9 parts sulphur. We are not certain about the translation of the paragraph in
relation to the proportion of copper added to the granulated bullion ; because in giving
definite quantities of copper to be added in the contingencies of various original copper
contents in the bullion, it would be expected that they were intended to produce some
positive ratio of copper and silver. However, the ratio as we understand the text in various
cases works out to irregular amounts, i.e., 48 parts of silver to 16, 12.6, 24, 20.5, 20.8, 17.8, or
18 parts of copper. In order to obtain complete separation there should be sufficient sulphur
to have formed a sulphide of the copper as well as of the silver, or else some of the copper
and silver would come down metallic with the " lump ". The above ratio of copper added to
the sulphurized silver, in the first instance would give about 18 parts of copper and 9 parts
of sulphur to 48 parts of silver. The copper would require 4.5 parts of sulphur to convert
it into sulphide, and the silver about 7 parts, or a total of 11.5 parts required against 9 parts
furnished. It is plain, therefore, that insufficient sulphur is given. Further, the litharge
would probably take up some sulphur and throw down metallic lead into the " lump ".
However, it is necessary that there should be some free metallics to collect the gold, and,
therefore, the separation could not be complete in one operation. In any event, on the above
ratios the " gold lump " from the first operation was pretty coppery, and contained some
lead and probably a good deal of silver, because the copper would tend to desulphurize the
latter. The " powder " of glass-galls, salt, and litharge would render the mass more liquid
and assist the " gold lump " to separate out.
The Roman silver sesterce, worth about z\ pence or 4.2 American cents, was no doubt
used by Agricola merely to indicate an infinitesimal quantity. The test to be applied to the
regulus by way of cupellation and parting of a sample with nitric acid, requires no explanation.
The truth of the description as to determining whether the gold had settled out, by using a
chalked iron rod, can only be tested by actual experiment. It is probable, however, that the
sulphur in the regulus would attack the iron and make it black. The re-melting of the regulus,
if some gold remains in it, with copper and " powder " without more sulphur, would provide
again free metallics to gather the remaining gold, and by desulphurizing some silver this
button would probably not be very pure.
