The Bozeman courier. (Bozeman, Mont.) 1919-1954, 1924-03-26

heres. The gold thus combined with
mercury is called "amalgam" and is
scraped off from time to time and re-
torted-that is, heated in a retort, the
quicksilver passing off as a vapor,
which is condensed and recovered, the
gold remaining. This gold is melted
into bars and shipped to the United
States assay office at Helena, Mon
tana, where it is bought by the gov
eminent.
After passing ove the copper plates
the pulp flows over concentrating
tables" and through flotation ma
chimes where the heavier particles,
containing most of the remaining gold,
in combination with iron, sulphur, and
arsenic, are separated. Thus separat-
ed, they are called Concentrates" and
until the arsenic plant hereinafter de-
scribed was installed, they were shin
ped to a smelter for the extraction Of
the gold. The smelter paid for the
gold, but did not pay for the arsenic.
AS the company's own arsenic plant
was commenced in January, only a
small quantity of the raw concen-
trates were shipped to the smelter III
1928.
The present practice is to roast the
concentrates and ship the residues,
which are called "calcines," and which
contain all of the gold which was
originally in the concentrates. The
arsenic plant was completed and put
in operation in March, 1923. 1t con-
sited at first of a reverberatory fur
! mace SKIS feet, on the hearth of
which the concentrates are spread, and
over which pass the flames from the
fire box. Part of the heat is fur
| nished by the combustion of the sui
phur contained in the concentrates.
The arsenic is driven off in the form
of a gas, and with the gases from the
furnace, passes into a series of cham.
bers, with steel roof, to facilitate "a
diation of the heat. When the tenn
perature of the gases gets down tC
about 218 degrees C, the arsenic con-
denses, and, seen through the peer
hole, looks like falling snOwflakes.
When the condensing chambers, (ol
Kitchens as they are called) are
conveniently full, the furnace is al,
lowed to cool, and the arsenic is SHOW
elled out of the kitchens onto the
floor. 1t is therefore wheeled back
to the same furnace in which it was
roasted, and roasted again, this time
with coke as afuel. Again it VIOLA
tilizes, and this time it is condensed
as a clean white powder containing
over SO per cent of white arsenic. This
is run through a grinding machine,
then, by the aid of a machine which
packs it tightly, is barrelled, and is
hauled by trucks to the railroad at
Gardiner, Montana, (6 miles, whence
it goes to the consumers in the east.
Filtered Through Bags.
The gases which have passed
through the kitchens, particularly dur
ing the operation of refining, contain
some arsenic; so that as soon as pos
sible a bag house" was erected with
in the building which houses the ar
senic plant. A bag house is simply a
filtering arrangement, in which are
suspended 48 wooden bags, each Is
inches in diameter and 80 feet long
through which the gases are forced
| by a large fan. The fine particles of
arsenic are caught in these bags, and
the filtered gas, mostly sulphur di-
oxide, diluted with air, is discharged
through the stack on the mountain
side, and causes no damage or incon-
venience. The bag house thus describ-
ed is a concrete structure 17x22 feet
and 45 feet high.
The reverbertory furnace has not
sufficient capacity to treat the concen-
trates capable of being produced in
the mill, and as it has to be used about
one-third of the time for refining
crude arsenic, was obviously too small.
Since, however, the arsenic business
had been shown to be a profitable one,
a larger furnace was plainly warrant
ed, and a new roasting plant was de-
signed after careful examination OF