IMPROVEMENTS IN THE MANUFACTURE OF CAUSTIC SODA AND OF CAUSTIC POTASH, AND IN APPARATUS THEREFOR.
Year: 1879

page_text: .
LETTERS PATENT to Willian Jones Menzies, of St. Helen's, in the County
of Lancaster, Chemical Manufacturer, for the Invention of "IMPROVEMENTS
IN THE MANUFACTURE OF CAUSTIC SODA AND OF CAUSTIC POTASH, AND IN
APPARATUS THEREFOR.
"
Scaled the 12th December 1879, and dated the 22nd September 1879.
PROVISIONAL SPECIFICATION left by the said William Jones Menzies at
the Office of tlie Commissioners of Patents on the 22nd September 1879.
WILLIAM JONES MENZIES, of St. Helen's, in the County of Lancaster, Chemical
Manufacturer. <<
IMPROVEMENTS IN THE MANUFACTURE OF CAUSTIC SODA AND OF
CAUSTIC POTASH, AND IN APPARATUS THEREFOR."
Hitherto caustic soda or caustic potash has been made (1) by causticising either
a solution of the carbonates of these alkalies or "black ash liquor" of a specific
gravity of about fifteen degrees Twaddle with the necessary equivalent of lime
by agitation, the resulting carbonate of lime afterwards being separated out by
decantation; or (2) carbonated liquor of thirty Twaddle has been taken and
mechanically agitated with lime under steam pressure with heat, and the carbonate
of lime afterwards separated out by decantation. When the first method is
employed a considerable amount of fuel afterwards is required to concentrate the
liquor; in the second method, besides the mechanical difficulties and danger of
agitating under steam pressure, there is a difficulty in thoroughly causticising the
liquor at the higher specific gravity owing to the fact that lime being more soluble
in cold solutions than hot (though assisted by the pressure) works with greater
difficulty at the higher temperature; there is also the greater mechanical difficulty
of separation afterwards of the stronger lyes, by decantation from the carbonate
lime, owing to their greater specific gravity; this is finally the case if any excess
of lime has been used. The causticisation of solutions of the carbonated alkalies
above fifteen Twaddle by the addition of a large excess of lime has also been
attempted, but the mechanical difficulty of settling out the carbonate and free lime
afterwards from the causticised lye, besides the loss of time, has prevented this
method being generally adopted. My improvements consist, first, in using hydraulic
pressure instead of steam, thereby facilitating the operation owing to the absence
of heat, and allowing a much higher pressure to be employed without risk of

page_text: explosion or accident, and whereby the process of causticisation is more perfectly
completed; second, in employing percolation under pressure instead of agitation,
as hereafter set forth; third, in conjunction with the above, the employment of an
excess of lime separated out from the causticised lye or converted into carbonate,
substantially as hereafter set forth.
The manner of conducting my process is as follows:-I take a carbonate of
soda or potash lye of thirty to forty degrees Twaddle, or even a higher strength,
I
depending on the pressure and lime used and the degree of causticity required;
mix with this lye a decided excess of slacked caustic lime beyond what is necessary
to completely causticise it. I pump this solution with a force pump into a tight
vessel with a mechanically constructed draining bed at the bottom; a steam boiler
placed either vertically or horizantally, fitted with a perforated false bottom with a
carefully constructed filtering bed of lime stone in several layers of different sizes,
from large pieces at the bottom up to quite small pieces at the top will do, or any
other suitable mechanical filtering bed can be adopted. From beneath the false
bottom I bring up a pipe so as to discharge the filtered liquor above the level of
the false bottom, and attach to it a suitable loaded valve of similar construction to
an ordinary steam boiler safety valve. In this manner an even pressure is main-
tained on both sides of the filtering bed. I commence the operation by filling up
the vessel entirely with water or causticised liquor from a previous operation; the
weight is then put on the loaded valve and set at the required pressure, this may
be safely carried up to eighty or one hundred pounds per square inch, according to
the specific gravity of the liquor required to be causticised or the degree of caus-
ticity required. The mixture of lime and carbonate soda or potash liquor is now
pumped in by a suitable force pump, the lime settles regularly on the filter bed or
strainer, and the liquor passing through is causticised both owing to the pressure
and being constantly exposed by admixture in settling, and also by percolation to
an excess of lime through which the liquor must pass as it is deposited on the filter
bed;
this manner of percolation through the lime is much more effective than any
mechanical agitation of the lye with lime; there is also a saving of fuel as no steam
is required to heat up the solution so as to bring it under pressure, and also a better
causticisation is obtained owing to the liquor being cold. As soon as the vessel is
nearly full of carbonate of lime, with caustic lime in excess, I pass through a
weaker solution of carbonate soda or potash lye, which is thus causticised, and at
the same time the excess of lime is converted into carbonate. When this is effected
I pump through water, with some carbonate of lime in suspension, in order to wash
out the last traces of alkali, and at the same time fill the vessel with carbonate
lime and bring it under hydraulic pressure; in this way a considerable amount of
water can be squeezed out of it, and the carbonate lime rendered much drier for
employment in the black ash process.
When this is completed, the carbonate lime can be removed from suitable man
holes in the vessel, and the weak liquors pumped on to the black ash vats, boiled
down, or used to dissolve fresh portions of carbonate soda or potash.
In the above process it will be obvious that the hydraulic pressure can be
obtained to a moderate extent by the black ash vats or pans for dissolving, the
carbonate being placed at a much higher level, and the column of liquor used instead
of the force pump, that if the required causticity is obtained by pressure alone the
excess of lime and subsequent removal by weaker liquors may be dispensed with,
that the filling up the vessel and pressing the "slutch lime" so as to make it more
solid may also be omitted, that the vessel may be partly filled with slacked lime
and the clear carbonate liquor pumped through it instead of the lime being pumped
in in suspension, also that the vessels may be worked to advantage in "sets" and
the liquor passed from one to the other.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Jones Menzies in the Great Seal Patent Office on the 22nd
March 1880.
WILLIAM JONES MENZIES, of St. Helen's, in the County of Lancaster, Chemical
Manufacturer. "IMPROVEMENTS IN THE MANUFACTURE OF CAUSTIC SODA AND OF
CAUSTIC POTASH, AND IN APPARATUS THEREFOR."
Hitherto caustic soda or caustic potash have been made (1) by causticizing either
à solution of the carbonates of these alkalies or black ash liquor" of a specific
gravity of about fifteen degrees Twaddle, with the necessary equivalent of lime by
agitation, the resulting carbonate of lime afterwards being separated out by
decantation; or (2) carbonated liquor of thirty Twaddle has been taken and
mechanically agitated with lime under steam pressure with heat, and the carbonate
of lime afterwards separated out by decantation. When the first method is
employed a considerable amount of fuel afterwards is required to concentrate the
liquor; in the second method, besides the mechanical difficulties and danger of
agitating under steam pressure there is a difficulty in thoroughly causticizing the
liquor at the higher specific gravity owing to the fact that lime being more soluble
in cold solutions than hot (though assisted by the pressure) works with greater
difficulty at the higher temperature; there is also the greater mechanical difficulty
of separation afterwards of the stronger lyes by decantation from the carbonate of
lime owing to their greater specific gravity; this is especially the case if any excess
of lime has been used. The causticization of solutions of the carbonated alkalies
above fifteen Twaddle by the addition of a large excess of lime has also been
attempted, but the mechanical difficulty of settling out the carbonate and free lime
afterwards from the causticized lye, besides the loss of time, has prevented this
method being generally adopted.
My improvements consist, first, in using bydraulic pressure instead of steam,
thereby facilitating the operation owing to the absence of heat and allowing a much
higher pressure to be employed without risk of explosion or accident, and whereby
the process of causticization is more perfectly completed; second, in employing
percolation under pressure instead of agitation, as hereafter set forth; third, in
conjunction with the above, the employment of an excess of lime separated out
from the causticized lyc or converted into carbonate, substantially as hereafter set
forth.
The manner of conducting my process is as follows:-I take a carbonate of soda
or potash lye of thirty to forty Twaddle or even a higher strength, depending on
the pressure, and lime used, and the degree of causticizity required; I mix with
this lye a decided excess of slacked caustic lime beyond what is necessary to com-
pletely causticize it. pump this solution with a force pump into a tight vessel
with a mechanically constructed draining bed at the bottom (a steam boiler placed
either vertically or horizontally, fitted with a perforated false bottom with a
carefully constructed filtering bed of limestone in several layers of different sizes,
from large pieces at the bottom up to quite small pieces at the top will do, or any
other suitable mechanical filtering bed can be adopted). From beneath the false.
bottom I bring up a pipe so as to discharge the filtered liquor above the level of
the false bottom and attach to it a suitable loaded valve of similar construction to
an ordinary steam boiler safety valve. In this manner an even pressure is main-
tained on both sides of the filtering bed. I commence the operation by filling up
the vessel entirely with water or causticized liquor from a previous operation, the
weight is then put on the loaded valve and set at the required pressure; this may
be safely carried up to eighty or one hundred pounds per square inch, according to
the specific gravity of the liquor required to be causticized or the degree of caus-
ticizity required. The mixture of lime and carbonate of soda or potash liquor is
now pumped in by a suitable force pump; the lime settles regularly on the filter

page_text: bed or strainer and the liquor passing through is causticized both owing to the
pressure and being constantly exposed by admixture in settling, and also by
percolation to an excess of lime through which the liquor must pass as it is
deposited on the filter bed; this manner of percolation through the lime is much
more effective than any mechanical agitation of the lye with lime, there is also a
saving of fuel, as no steam is required to heat up the solution so as to bring it
under pressure and also a better causticization is obtained owing to the liquor being
cold.
As soon as the vessel is nearly full of carbonate of lime, with caustic lime in
excess, I pass through a weaker solution of carbonate of soda or potash lye, which
is thus causticized, and at the same time the excess of lime is converted into
carbonate. When this if effected I pump through water with some carbonate of
lime in suspension, in order to wash out the last traces of alkali, and at the same
time fill the vessel with carbonate of lime and bring it under hydraulic pressure;
in this way a considerable amount of water can be squeezed out of it and the
carbonate of lime rendered much drier for employment in the black ash process.
When this is completed the carbonate of lime can be removed from suitable man-
holes in the vessel and the weak liquors pumped on to the black ash vats, boiled
down, or used to dissolve fresh portions of carbonate of soda or potash. In the
above process it will be obvious that the hydraulic pressure can be obtained to a
moderate extent by the black ash vats or pans for dissolving, the carbonate being
placed at a much higher level and the column of liquor used instead of the force
pump; that if the required causticizity is obtained by pressure alone the excess of
lime and subsequent removal by weaker liquors may be dispensed with; that the
filling up the vessel and pressing the "slutch lime so as to make it more solid
may also be omitted; that the vessel may be partly filled with slacked lime and
the clear carbonate liquor pumped through it instead of the lime being pumped in
in suspension; also that the vessels may be worked to advantage in "sets" and the
liquor passed from one to the other.
"
Figs. 1 and 2 illustrate my Invention. In these A is a vat into which the milk
of lime and carbonate liquor are passed and are thoroughly mixed by stirrers from
above, if desirable, but in all ordinary cases these stirrers are not required. B is a
pipe leading to the pump C worked by engine D in Drawing, though manual or
other power can be applied instead. Pump pumps the liquor up pipe E into
chamber F; on its way it passes through contracted portion of pipe G. The object
of this contracted portion is to prevent the pump pumping too strong a stream and
disturbing the bed. Other arrangements for the same purpose could be used, and
in all cases the diameter of the pipe where it enters chamber F had better be
larger than its minimum diameter after leaving the pump. H is the limestone
placed in the perforated false bottom J, coarse lumps at bottom and smaller above,
up to finely granulated stuff on the top, upon which is placed a layer of caustic
lime or carbonate of lime a few inches thick, say four inches at starting; K, man-
holes;
L, exit pipe for causticized liquor, weighted with safety valve M and also
provided with a weighted valve, not shown, so that it cannot discharge its contents
except at a given pressure. It will be seen at once that after once filling the
chamber F with causticized liquor the action of the apparatus can be accurately
regulated by regulating the speed of the pump (up to the point where the contracted
pipe puts in its veto, and which point is far in excess of requirements).
Having now described my Invention and the best mode known to me of carrying
it into effect, I wish it to be understood that what I believe to be new and desire
to protect by the hereinbefore in part recited Letters Patent is,
First. The causticization of carbonate of soda or potash lyes under hydraulic
pressure or head, together with percolation through the causticizing material with
or without excess of lime in solution or suspension; also the subsequent treatment
of the residual carbonate of lime by washing and pressure, substantially as
described.
Second. The causticization of carbonate of soda or potash lyes by bringing them
into intimate contact with lime either by percolation, or mechanical mixture, or

page_text: both, at a temperature at or below the ordinary temperature of the atmosphere and
under a high static pressure.
In witness whereof, I, the said William Jones Menzies, have hereunto set
my hand and seal, this Eighteenth day of March, in the year of our Lord
One thousand eight hundred and eighty.
Witness,
WP. THOMPSON,
Patent Agent,
6, Lord Street,
Liverpool, &
323, High Holborn,
London, W.C.
W. J. MENZIES.
(L.S.)