Getting Gold

inary mercuric amalgamation or lixiviation. The effect of the roasting is first to sublimate and drive off as fumes the sulphur and a proportion of the objectionable metals. What is left i

will not amalgamate with mercury, and a

rature that will induce oxidation. No appreciable effect follows the mere contact of air with sulphur particles at atmospheric temperature; but if the particles be raised to a temperature of 500 degrees Fahr., the sulphur is

es, having been crushed to a proper degree of fineness, are raised to a su

ting will be one that enables the particles to be thoroughly o

practical use may be div

ose the upper surface of the ore to contact with air the material is turned over by manual labour. This furnace of the reverberatory type is pro

ernally lined with refractory material. It has projections that cause the powdered ore to be lifted above the flame, and, at a certain height, to fall

re under treatment; it may vary from two revolutions per minute down to one revolution in thirty minutes.

diameter of 4 ft. 6 in., inclined 1 ft. 6 in. in it

r provided at the side of the furnace. Openings provided at each end of the furnace permit the passage of the flame through it, and the revolution of the furnace turns over the powdered ore and brings

through the centre of a vertical shaft up which a flame ascends; the powdered ore in falling through the flame

the fall of the ore is checked by cross-bars or inclined plates placed acro

idation to be obtained. The oxidation or burning of the sulphur will provide all the heat necessary to maintain the continuity of the process. The temperature necessary for effecting the elimination of both sulphur and arsenic is not higher than that

ENT CLASSES THAT ARE IN ACTUAL

eously employed in this furnace, which is fired with gaseous fuel. The sensible heat of the waste gases is utilised to heat the air employed for combustion; and by a controllable arrangement of combustion, a flame of over 100 feet in length is obtaine

maximum near the firing end, and tails off at the extreme gas outlet end. The ores in this furnace should ther

at it is impossible to avoid the incursion of air during the

rlance as a "sweet roast" (because a perfectly roasted ore is nearly odourless) varies considerabl

chanically to effect the rabbling. One of the most successful is that known as t

ixed in the centre of the furnace and having laterally projecting arms, car

e, and half are resting in the cooling space, so that a co

r than other mechanically stirred reverberatory furna

ble and should be avoided, but the horse-shoe type

OLVING CYLIN

The Howell-White, the Bruckner, the

urning on the horizontal axis

about four tons. When the two charging doors are brought under the hop

sufficiently to allow the flame evolved from a gra

ength of 12 feet and a diameter of 6 feet. A furnace of this capa

f the ore under treatment and the nature of the fuel employed. Four hour

uch of its constituents as are amenable to the action o

ent almost impossible. I know a case in point where an average of nearly five ounces of silver to the ton, at that time worth 30s., was lost owing to ignorance on this subject. Had the ore been calcined with salt, NaCl, the bul

der, averaging 25 feet in length and 4 ft. 4 in. in diameter, which revolves o

g the revolution should not exc

he powdered ore to be raised over the flame through which it showers, and is

rom the higher to the lower end. It is fed into the upper end, by a special form of feed hopper,

ever, made in segments to be afterwards bolted

lt at the lower end; it is more economical both in fue

which is fired with gaseous fuel, is stated to combine the ad

r, their ends terminating in two vertical shafts of brickwork, by which the three cylinders are connected. The powdered ore is fed in

eries and the ore is reduced by the expulsion of its sulphur, arsenic, etc., as it descends from the top to the bottom. The top cylinder is ma

howers through the flame, falling in its descent a distance of over 100

oxidising treatment to be controlled exactly as desired so as to effect the best results with all kinds of ore

epends, of course, upon the nature of the ore, but may be considered to range within the limits of twelve to fifty tons in twe

ute control over the temperature in the furnace, but the use

the Thwaite-Denny furnace is

to keep the ore agitated; and spiral flanges convey it to the outlet end continually, shooting it across the cylinder. The cylinder is encased in a brick furnace. The firing is provided from outside, the inventor maintaining that the products of combustion are inimical to rapid oxidisation, to specially promote which he intro

work with outside heat, but I

FT TYPE

t clear fall the descent is impeded by inclined planes placed at different lev

power is required and the structure of the furnace is of a durable character. Its disadvantages ar

etefeldt's furnac

roast from 40 to

ill roast from 20

roast from 10 to

entrates so as to be innocuous to mercuric amalgamation. The sulph

hould be roasted in a revolving furnace in thirty

quare inside at the base, tapering to 2' 6" at the summit, will require 12,000 red bricks, and 1

neys lies in the convenience of removal and erection. They should be made in sections of 20 feet long, three steel wire guy-ropes attached to a ring, rivete

ea of the chimney flue, and ten to twenty feet long, can be built of brickwork, set in cement; the walls are provided with a cavity, filled with sand or Portland cement, so that there will be no danger of the incursion of air. In all furnace work the greatest possible precautions should be taken to preven

s of the most recen

d in other methods

o Dr. T. K. Rose's "

d ed