AURVM. 203
from the addition of sufficient silver to
the mass to constitute three-quarters of the weight. The mixed metal
being immersed in nitric acid, the silver is attacked and dissolved
into powder, the gold remaining intact in the form of a spongy mass.
Mentioning its extreme infu-sibility, Pliny adds that the best material
for melting gold (which resisted the hottest charcoal-fire) was paleœ, or
straw that has been threshed—a strange fact, if correct, which he again
adduces in his notice of the best materials for smelting the various
metals (xxxiii. 30).
The
process used for refining gold in the mint of Delhi in the middle of
the sixteenth century, was as simple as the ancient Egyptian, and yet
perfectly adequate to its purpose, as the purity of the magnificent
coins thence issued convincingly declares. It is thus detailed in the '
Ayeen Akbary:'—"The adulterated gold (i.e., the collected pieces of
different qualities) is made into plates of six or seven mashaL· weight
by the plate-maker. These he carries to the assay-master, who measures
them in a mould made of copper ; then he makes a stamp upon them. . . .
When the above-mentioned plates have been stamped, the owner of the
gold for the weight of every hundred gold mohurs must furnish four
seers of saltpetre, and the like quantity of new brick-dust, which are
to be used in the following manner :—The plates, after having been
washed with water, are stratified with the above mixture, and the whole
is covered with field cow-dung, which in the Hindostany language is
called miplah. Then they set fire to it, and let it burn gently
till the cow-dung is reduced to ashes, when they leave it to cool ;
then these ashes, being removed from the sides (of the plates), are
preserved. In Persian this is called khak kheass, and in Hindostany solony ; and, by a process which will be hereafter related, they recover silver from it.
