IMPROVEMENTS IN THE MANUFACTURE OF ALKALINE SULPHATES
Year: 1875

page_text: LETTERS PATENT to James Cochran Stevenson, of South Shields, in
the County of Durham, Alkali Manufacturer, for the Invention
of "IMPROVEMENTS IN THE MANUFACTURE OF ALKALINE SULPHATES"
of
"IMPROVEMENTS IN THE MANUFACTURE OF ÅLKALINE SULPHATES
"
PROVISIONAL SPECIFICATION left by the said James Cochran
Stevenson at the Office of the Commissioners of Patents, with his
Petition, on the 8th May 1875.
I, JAMES COCHRAN STEVENSON, of South Shields, in the County of
Durham, Alkali Manufacturer, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN THE MANUFACTURE OF ALKALINE SULPHATES,"
to be as follows:-
This Invention relates to the preparation of common salt to be used
in the process Patented by Messieurs Hargreaves and Robinson for the
manufacture of sulphate of soda by exposing common salt to the action
of sulphurous acid.
The salt is moulded by pressure into lumps, by preference in a
machine such as is used for the manufacture of bricks, by the com-

page_text: pression of ground clay, and the compressed and moulded lumps are
afterwards hardened by heat.
I find that pan salt or ground rock salt, or a mixture of the two, may
be compressed, as above described, into lumps which will bear handling
prior to their being hardened by heat.
I prefer to mould the salt into lumps of the shape of a sphere. Such
balls should leave the machine of sufficient hardness to roll or slide
without breaking down an inclined plane or inclined grooves on to the
receiving plate of an oven provided with an endless series of drying
plates, such as is used for firing biscuits made by machinery. The balls:
are carried through the oven on the drying plates, and are hardened by
the heat.
I find that these balls of salt may be conveniently made of a diameter
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said James Cochran Stevenson in the Great Seal Patent
Office on the 6th November 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JAMES
COCHRAN STEVENSON, of South Shields, in the County of Durham,
Alkali Manufacturer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eighth day of May, in the year of our
Lord One thousand eight hundred and seventy-five, in the thirty-eighth
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said James Cochran Stevenson, Her special license
that I, the said James Cochran Stevenson, my executors, adminis-
trators, and assigns, or such others as I, the said James Cochran
Stevenson, my executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times
thereafter during the term therein expressed, should and lawfully
might make, use, exercise, and vend, within the United Kingdom of
Great Britain and Ireland, the Channel Islands, and Isle of Man,
an Invention for "IMPROVEMENTS IN THE MANUFACTURE OF ALKALINE

page_text: SULPHATES," upon the condition (amongst others) that I, the said
James Cochran Stevenson, my executors or administrators, by an
instrument in writing under my, or their, or one of their hands and
seals, should particularly describe and ascertain the nature of the said
Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Seal Patent Office within six
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said James Cochran Stevenson, do
hereby declare the nature of the said Invention, and in what manner
the same is to be performed, to be particularly described and
ascertained in and by the following statement thereof, that is to
say :—
This Invention relates to the preparation of common salt to be used
in the process Patented by Messrs. Hargreave and Robinson for the
manufacture of sulphate of soda by exposing common salt to the action
of sulphurous acid.
The salt is moulded by pressure into lumps, by preference in a
machine such as is used for the manufacture of bricks, by the com-
pression of ground clay, and the compressed and moulded lumps are
afterwards hardened by heat.
I find that pan salt or ground rock salt, or a mixture of the two,
may be compressed into lumps, as above described, and that salt of the
ordinary degree of dampness may be used without the addition of
water.
The moulding machine, which is similar to that used in the manu-.
facture of bricks by the compression of ground clay, consists of a
cylinder 3 feet long and 2 feet in diameter, turning on a horizontal
axis and provided (one at each quarter of its circumference). with
four longitudinal rows of plungers working in cylindrically shaped
recesses 2 inches in diameter. There are 10 plungers in each row.
The heads of the plungers may be made flat, but I prefer them
hollowed out so as to form cavities or cups somewhat shallower than a
hemisphere, in order to give a rounded shape to the lower or (with
reference to the cylinder) inner half of the moulded lumps of salt..
The salt is supplied from a hopper, and the circumference of the
cylinder prevents the salt running out of the hopper..

page_text: Each row of plungers in succession passes and is stopped opposite the
lower part of the hopper, which is kept full of salt, and a row of
ten horizontal pins working in the hopper push the salt without pressure
into the 10 recesses so as to fill them with salt; then a quarter revo-
lution of the cylinder brings the recesses so filled under a row of moulds
with cavities like those on the ends of the plungers. These moulds or
inverted cups are fixed on a horizontal bar and supported by strong
springs. This bar is placed above the highest part of the cylinder, and
the downward movement of the bar causes compression of the salt in
the recesses between the moulds or cups on the bar and the hollowed
ends of the plungers. A further quarter revolution of the cylinder
brings the plungers into a horizontal position, in which they are moved
outwards and push the moulded lumps of salt out of the recesses so as
to be gently received on a travelling web. The detaching of the lumps
from the ends of the plungers is aided by the descent of a horizontal
bar with india-rubber on its lower edge, which by gently touching the
balls, liberates them from the plungers without breaking them.
The travelling web is made of thin sheet iron straps 3 of an inch
wide placed an inch apart and carried by two leather bands. The
bands pass over two moving horizontal drums 6 inches in diameter,
which give the travelling motion to the web.
The web conveys the moulded lumps of salt on to the nearest plate
of an endless series of cast-iron plates working in an oven 40 feet long
and 5 feet wide, and the lumps thus carried through the oven are
When the
delivered at the further end dried and hardened by the heat.
oven is at a temperature of 500° Fahrenheit the lumps are dried in
passing through in half an hour.
I find that the lumps of salt do not adhere to the fixed moulds and
to the plungers if the moulds and plungers, where they touch the salt,
are made of brass or gun metal, and if the middle portion of the ball is
made cylindrical, and the rounded ends are consequently moulded flatter
than a true hemisphere.
I find that the balls may be conveniently made of a diameter
of two inches, but I do not restrict myself to any particular size or
shape.
As the length of the row of plungers is only half the width of the
oven the travelling web is made as wide as the oven, and the balls are

page_text: guided diagonally as they pass along the web by strips of iron fixed
above the web, so that the balls may be evenly distributed on the plates
of the oven.
I claim the preparation of salt for the manufacture of sulphate of
soda by moulding it into lumps and hardening the lumps by heat, sub-
stantially as described.
In witness whereof, I, the said James Cochran Stevenson, have
hereunto set my hand and seal, this Fifth day of November,
in the year of our Lord One thousand eight hundred and
seventy-five.