Elements of the Theory and Practice of Chymistry, 5th ed.Macquer, Pierre Joseph
History
Elements of the Theory and Practice of Chymistry, 5th ed.
Macquer, Pierre Joseph
Chemistry -- Early works to 1800
One of the speediest and easiest methods to deprive this Gold of its
fulminating quality, is to grind in a mortar twice as much flowers
of Sulphur as you have Gold to reduce, mixing your fulminating Gold
therewith by little and little, as you grind them together; then to
put the mixture into a crucible, and heat it just enough to melt the
Sulphur. Part of the Sulphur will be dissipated in vapours, and the
rest will burn away. When it is quite consumed, increase the fire so
as to make the crucible red-hot. When you perceive no more smell of
Sulphur, pour on the Gold a little Borax, previously melted in another
crucible with a Fixed Alkali, as calcined Wine-lees, or Nitre fixed
with Tartar; and then raise the fire sufficiently to make the whole
flow. After the fusion is completed, you will find a button of Gold at
the bottom of the crucible under the Salts.
Fulminating Gold may also be reduced by pouring on it a sufficient
quantity of Fixed Alkali reduced to a liquor, or of oil of Vitriol,
evaporating all the moisture, and gradually throwing what remains,
mixed up with some pinguinous matter, into a crucible kept red-hot in
a furnace. The reason why these substances deprive the Gold of its
fulminating quality, depends on the causes that produce the fulmination.
Gold may also be separated from _aqua regis_, and precipitated by the
means of several metallic substances that have a greater affinity,
either with _aqua regis_, or with one of the two Acids that compose it.
Mercury is one of the fittest for this purpose. On dropping a solution
of Mercury in the Nitrous Acid by little and little into a solution of
Gold, the mixture becomes turbid, and a precipitate is formed. Continue
dropping in more of the solution of Mercury till no more precipitate
falls; then let the liquor stand to settle, and at the bottom of it
you will find a sediment, which is the precipitated Gold: pour off the
liquor by inclination, and wash the precipitate with fair water.
Public-domain text, read in full here on John Shaqi.
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