CERTAIN APPARATUS FOR ROASTING AND CALCINING ORES AND MINERALS, AND SEPARATING METALS THEREFROM, WHICH APPARATUS IS IN WHOLE OR IN PART APPLICABLE TO THE DRYING AND ROASTING OF MALT AND OTHER VEGETABLE SUBSTANCES
Year: 1854

page_text: PROVISIONAL SPECIFICATION left by. William Littell Tizard. at the Office,
of the Commissioners of Patents, with his Petition, on the 28th April
1854...
I, WILLIAM LITTELL TIZARD, of Aldgate, in the City of London, Engineer;
do hereby declare the nature of the said Invention for "CERTAIN APPARATUS
FOR ROASTING AND CALCINING ORES AND MINERALS, AND SEPARATING METALS
THEREFROM, WHICH APPARATUS IS IN WHOLE OR IN PART APPLICABLE TO THE DRYING
AND ROASTING OF MALT AND OTHER VEGETABLE SUBSTANCES," to be as follows:-
This apparatus is designed more especially to surmount the difficulties
hitherto experienced in extracting gold from ores that contain a superfluity of
arsenic, antimony, lead, tin, and other metals, the presence of which when in
contact with mercury prevents the amalgamation of the latter with gold. It
is also serviceable in roasting copper and other ores, but is here particularly
described as operating on minerals containing gold. The apparatus is con-
structed as follows:-An iron cylinder of any desirable dimensions, open at
both ends and lined with fire brick, stands upright on a suitable base; (when
made upon a large scale, it may be built of brick or stone and made conical,
with its sinaller end uppermost, to increase its stability.) In the centre of the
cylinder is placed a vertical shaft, working -on-its toe-and--kept in a central

page_text: position by a bearing on a cross bar fastened on the top of the cylinder.
Around this shaft is fixed a spiral floor, coiling from top to bottom, each coil
from 6 inches to 12 inches apart. The spiral floor is perforated and turned up a
few inches at its outer edge; each perforation is convex on the upper side of the
floor and concave underneath. The floor is also provided with two or more
shallow strips, which radiate from the centre to its periphery. In the angle
formed by the lower strip and the outside of the spiral floor are two or more
small holes and in the angle formed by the upper strip and the inside portion
of the floor, are similar holes; the intermediate strips are bent near the
middle, and there are holes near the cavities so formed.
A suitable furnace is placed at or near the base of the cylinder, and the top
of the latter is surmounted by a chimney. A perforated spout connects the
lower part of the cylinder with a pulverizing and amalgamating machine, and
just over this spout is a cold water tank, in the bottom of which is a perforated
or rose-head pipe. Commanding the spiral floor is placed a-pair of powerful
corrugated or plain (the former preferred) rolls, with a hopper and a spout, to
deliver the broken material into the upper part of the spiral floor. A crank
pin is fixed into one of the spur wheels or into the end of the axle of one roll,
and a lever is fastened to the vertical axle of the floor, and the crank pin and
lever are united by a connecting rod..
Having thus described the construction of the apparatus, I will now procced
to explain the manner in which it is worked. A fire being made in the furnace,
the hot air arising therefrom ascends on both sides of the spiral floor. Motion
being given to the rollers, they revolve, and a shaking effect is imparted to the
spiral floor. The rollers are fed with quartz or ore, which is crushed into small
pieces and gradually shaken down the spiral floor, where it becomes heated in
its transit to the bottom by the ascending fire. The hot ore now passes
through the perforated spout, and is there quenched by the falling jets of water
from the tank above. The ore thus roasted and partially cooled, gravitates
into the pulverizing and amalgamating machine, where it arrives-divested-of
its arsenical compounds, tin, lead, and all other readily fusible metals that may
have been present, and in a state sufficiently friable to be pulverized and washed,
the precious metal being either amalgamated or precipitated. The perforations
in the spiral floor are to admit a portion of the hot air through the ore, and the
strips, before noticed, are for the purpose of intercepting and carrying off in a
separate state, such metals, particularly lead and tin, as may be melted and
extracted from the descending ore. In this apparatus a tolerably perfect
separation of the superfluous metals is ensured by the varied temperature of

page_text: the ascending fire. For example: arsenic is dissipated at a comparatively low
temperature, between, say, 200 and 300 degrees; tin melts at about 400
degrees, while lead requires upwards of 600 degrees to release it from its
matrix. The first of these metals therefore becomes volatilized before it
reaches one-third down the spiral floor; the tin flows away on reaching about
half way down, while the lead will be deposited in a fluid state near the fire
beneath.
The apparatus before described is applicable also, with slight modifications,
to the drying and roasting of malt and other vegetable substances.