gold, after most careful washing, is boiled in a platinum vessel for a
short time, with a further proportion of concentrated sulphuric acid,
after which the washing is repeated, and the gold is dried, melted,
and cast into bars. The melting was performed in “ Piccardic pots,”
and my friend, Professor Roberts, of the Royal Mint and Royal
School of Mines, pointed this out as remarkable, as the fusion of
gold is now, as a rule, performed in the best and strongest plumbago
crucibles, it being very risky to fuse gold in a clay pot.
The acid liquors containing argentic and cupric sulphates are next'
treated for the recovery of the silver. The liquid contained in a
vessel lined with lead is diluted, and then heated by the passage of
steam from a boiler through perforated leaden pipes into the solution.
The sulphate of silver dissolves in the boiling water, and is precipitated
therefrom by the introduction of scrap copper, the reduction
being continued until the solution ceases to give a white, “ curdy ”
precipitate upon the addition of a solution of salt. The solution of
cupric sulphate is run off by a syphon to the crystallizing tanks, and
the finely divided precipitated silver is washed and afterwards compressed
into cakes with a hydrauhc press, which is also, used for the
expulsion of water. The cakes, after drying, are melted in “ Piccardic
pots ” and cast into bars. All these operations, except the fusions,1
are.conducted in one large room, and during the whole of the boilings
with sulphuric acid large quantities of sulphurous and sulphuric
anhydrides, together with volatilized sulphuric acid, are given off. Ho
attempt whatever is made to condense the fumes, and the workmen
engaged are-exposed all day to the deleterious gases and vapours.
There is not even a good draught to carry away the fumes into the
air, in spite of a very tall chimney which is constantly pouring forth
clouds of black smoke and contributing an important quota to the fogs
of the metropolis. When Messrs. Rothschild’s neighbours complain,
the millionaire proprietors silence them with the present of a bar oi
silver or gold, according to the importance of the complainant.
From this scene of precious metal and had vapours, I passed on to
the crystallizing tanks, situated in large vaults underground. Here
the crystallization of the sulphate of copper goes on. Gras jets threw
light on great walls of blue, tanks of blue; and innumerable facets of
blue crystals flashed back the illumination with singularly beautiful
effect. Monte Cristo’s cavern could hardly have appeared at first
blush more strangely impressive. Some of the crystals were eight,
and even ten, inches long, and of a most perfect form. There were
several tons of sulphate of copper stored in the drying-room, and !
asked the director what market he had for such vast quantities of
an article which, to me, seemed of so little use. “ Pour les marchands
de 1pickles,’ ” he said, smiling.
Messrs. Rothschild’s works, it is said, only just pay their expenses
as a refinery. I am told they are only carried on as a purely financial
matter, in order to enable the owners to flood the markets of Hamburg,
Paris, Berlin, or other of the important‘commercial centres of Europe,
with a million of money at almost a moment’s notice. A large quantity
of the pure gold and silver produced is, however, sent into the Royal
Mint, which is situated almost next door to Rothschilds. Having
taken leave of the courteous director of Rothschilds, I proceeded,
under the guardianship of the well-known Professor Roberts, F.R.S.,
to her Majesty's Mint. Here I saw the chlorine system of parting
gold and silver. This process obviates the expensive necessity for
alloying the gold with two or three times its weight of silver, for no
other purpose than to insure success in the process of parting. The
gold containing silver is melted in a plumbago crucible, fitted with a .
lid with an aperture to receive a clay pipe connected by tubing with
an apparatus for generating chlorine gas. The clay pipe is passed to
the bottom of the melted mass of gold, the surface of the latter being
covered with a layer of borax, which thus acts as a condenser and
prevents the loss of metal by volatilization. The chlorine, as it passes
through the molten metal, is at first quickly absorbed, attended hv the
conversion of the traces of arsenic, antimony, bismuth, lead, &c., into
their respective chlorides. The silver present is also converted into
chloride, and, rising to the surface, forms a layer of fused argentic
chloride. The first stage of the operation is marked by the escape
of white vapours, consisting of chlorides of the baser metals, and
after a while orange-coloured vapours begin to appear, indicating
that the process is complete. The crucible is then withdrawn, and
the gold allowed to set, when the still fluid argentic chloride is
poured out into a flat mould (a slab of suitable form) for its subsequent
reduction by iron and diluted acid—sometimes by carbonate
of soda. The gold is cast into ingots suitable for rolling for sovereigns..
The day I visited the Mint they were making nothing but shillings ;
this, however, is a typical process, and a description of it will he prac-,
tically a description of the coining of all the other pieces. The alloy
of silver and copper and a trace of unremoved gold is melted in a
plumbago crucible capable of* holding 200 ounces. By a suitable
mechanism of cranes and levers, the pot is lifted bodily from the furnace
and its contents poured into a row of ingot moulds fixed on a,.,
E 2