IMPROVEMENTS IN THE MANUFACTURE OF SODA AND POTASH
Year: 1869

page_text: LETTERS PATENT to William Robert Lake, of the "International
Patent Office," No. 8, Southampton Buildings, Chancery Lane, in
the County of Middlesex, Consulting Engineer, for the Invention
of "IMPROVEMENTS IN THE MANUFACTURE OF SODA AND POTASH."-A
communication from abroad by François Marie Bachet, of Paris,
in the Empire of Emance Bankor
Scaled the 18th September 1869, and dated the 29th March 1869.
PROVISIONAL SPECIFICATION left by the said William Robert Lake
at the Office of the Commissioners of Patents, with his Petition,
on the 29th March 1869.
I, WILLIAM ROBERT LAKE, of the "International Patent Office,"
No. 8, Southampton Buildings, Chancery Lane, in the County of
Middlesex, Consulting Engineer, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN THE MANUFACTURE OF SODA AND
POTASH," a communication, to be as follows:-
My Invention consists in an economical process of manufacturing
soda and potash. This process of manufacture is based,-

page_text: First. Upon the known decomposition of chloride of sodium and
chloride of potassium by the oxide of lead in the presence of water at
the ordinary temperature. By this decomposition is formed on the one
hand an oxichloride of lead or more correctly speaking a mixture of
chloride of lead and hydrate of oxide of lead (solid), and on the other
hand caustic potash or soda which remains in solution. This solution
separated from the solid part is evaporated to withdraw it from the soda
or potash.
Second. Upon the augmentation heretofore unknown and very
remarkable in the production of soda and potash, which is caused in
this operation by the adjunction of lime.
Third. Upon the action of the lime or any other analogous alkali in
water at the boiling point on the oxichloride of lead, or the mixture of
chloride of lead and the hydrated oxide of lead resulting from the first
operation, for bringing the one or the other into the condition of oxide
of lead suitable for recommencing a fresh reaction upon the chloride
of sodium or potassium. In this ebullition chloride of calcium is formed
in solution in the liquid, which is separated and thrown away.
Fourth. Upon the combination of these two reactions which may be
continued indefinitely so that the same oxide of lead may (except a
slight loss to be made up) decompose an indefinite number of fresh
quantities of chloride of sodium or of potassium, furnishing therefrom
the soda or potash. The only expense incurred is that of the chloride
of sodium or of potassium, the lime and fuel.
I will now describe the manner of proceeding for the manufacture of
soda according to my system. The same details are applicable to the
production of the potash, the chloride of sodiumm being replaced by that
of potassium.
The first operation is as follows: I pulverize as completely as
possible a quantity of litharge. The manner in which this pulverizing
is effected greatly influences the quantity of the soda produced. To
this litharge is added water, lime slaked or well pulverized, and sea salt.
This mixture is stirred for some hours at the ordinary temperature and
becomes quite white, at this moment the reaction is finished.
proportions of the different substances may be varied, but the following
have produced good results:-To a hundred parts by weight of litharge I
add from twenty-five to fifty of lime. In producing the soda the
quantity of water appears to be immaterial within certain limits, but it
The

page_text: is obviously advantageous to employ as little as possible so as to have a
liquid more strongly sodaized and to have as little water as possible to
evaporate. With from once or twice the weight of the litharge, that
is to say,
from one hundred to two hundred parts, a paste may be formed
which will be easy to stir with the implement used for that purpose. As
to the quantity of sea salt it serves to use a quantity equal at first to
that which the water employed can dissolve, and then to add so much
to that which should be decomposed that the liquid is always fully
charged. An excess of this substance will do no harm. When the
operation is finished there will be found, by weighing, in the liquid a
quantity of soda equal on an average to ten per cent. of the weight of
the litharge used; there will be more or less according to the quality of
the materials and the degree of perfection of the work. These ten
parts of soda correspond to about thirteen parts of hydrate of soda;
without the addition of the lime the production of soda is four or five times
less. The reason of this is probably that the chloride of lead is nearly
insoluble in the lime water while it is slightly soluble in pure water, and
this insolubility, which is occasioned by the presence of the lime, prevents
it to some extent from being attacked by the soda already formed, which
converts it into hydrated oxide of lead in reproducing chloride of sodium.
This counter action operating at the expense of the soda already
produced, it will be understood that with the above-mentioned use of
the lime there will be found in the end a much larger quantity of soda.
This implies that the oxichloride of lead, the result of the operation, is
not by any means a compound with definite proportions, but a simple
mixture with variable quantities of chloride of lead and of hydrated
oxide of lead. This is also confirmed by other experiments. Whatever
else may be the value of this theory the new fact which I make known
certainly exists, namely, that the addition of lime in the reaction of
sea salt upon oxide of lead gives a considerably superior production of
soda. When the operation is finished the soda liquid is withdrawn from
the paste by filtration and washing; filters of porous earth serve for this
object. By this means I obtain a liquid charged with from five to ten
per cent. of soda, containing also a great quantity of sea salt and a small
quantity of lime and oxide of lead all in solution. By properly conducted
evaporation I withdraw successively these various substances to make
them re-enter into the following operation, and I obtain therefrom a
definite quantity of pure hydrate of soda, which only becomes solid after
total evaporation.

page_text: In the second operation the paste remaining in the filter after being
well washed to get rid of all the soda which it contains is put in a vat
with a proper quantity of water and is made to boil during about six
or eight hours. The lime remaining in this paste reacts, as has been
said, upon the chloride of lead and the hydrated oxide of lead, and
brings the one and the other to the condition of oxide of lead suitable
for further reaction upon the sea salt, while it forms on the other hand
chloride of calcium. When the boiling is finished it is allowed to
deposit. The deposit is effected very rapidly and without allowing it to
cool I decant the clear liquid which I put on one side; I then perform
a second washing, the water of which is also put aside. The first water
withdrawn presents the following phenomenon:-In proportion as it
cools the chloride of calcium reacts upon the oxide of lead which it holds
in solution, and the chloride of lead and lime will be seen to precipitate
in numerous flakes. This precipitate is withdrawn by decantation to
make it re-enter into the next operation of regeneration. The liquid
poured off is mixed with the washing water, and it acts to withdraw from.
this mass all the oxide of lead which it retains in solution to prevent the
loss of any valuable matter. I now proceed as follows:-I pour gently
and with constant agitation hydrochloric acid up to the moment when the
test paper gives its first indication of acid; at this instant the liquid has
become perfectly limpid and only contains chloride of lead and chloride
of calcium; I then pour with constant agitation lime water till the test
paper gives a free alkaline indication. The insolubility herein-before
mentioned of the chloride of lead in lime water causes the precipitation
of all of this chloride. This is withdrawn by decantation to make it
re-enter into the first following operation of regeneration, and the liquid,
which no longer contains anything but chloride of calcium, is without
value and may be thrown away. The oxide of lead regenerated in the
above operation is employed in a fresh operation of sodification with the
quantities mentioned of water and sea salt; I add besides a quantity of
lime equal to that carried off in solution by the washings plus the
quantity transformed into chloride of calcium. This series of operations
may be renewed indefinitely and furnish cach time the quantities of
soda indicated.
The third operation is the calcination. In all the preceding operations
it is well to avoid as much as possible the contact of the air. The
carbonic acid contained therein is strongly attracted by the soda, the

page_text: lime, and the oxide of lead. It is fixed definitively by the lime, but the
carbonate of lime thus formed is injurious, for on the one hand it will
no longer act as caustic lime, and on the other hand it envelopes the
grains of oxide of lead and prevents their reaction upon the sea salt.
Nevertheless it would be very difficult for any length of time to guard
entirely against this accidental carbonization. It is therefore desirable
from time to time to proceed with the ejection of this carbonic acid,
which I perform in the following manner:-I take the paste at the
monent when it comes from the operation of regeneration and when in
consequence it contains no chloride of lead but only oxide of lead, lime,
and carbonate of lime; it is then calcined at a red heat for at least
three hours; though the oxido of lead is fused the paste will not run
because of the quantity of lime that it contains, so that the operation is
rendered very easy. The paste then becomes hard, compact, and of a
greenish yellow colour, and the carbonic acid is driven off; it must then
be ground completely till it re-assumes a clear green color. A little
water assists the grinding; it is then ready to be used in the operation
of sodification. When the paste has been subjected to this calcination
it is more concrete and serves better for the filtration and washing.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Robert Lake in the Great Seal Patent
Office on the 28th September 1809.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
ROBERT LAKE, of the "International Patent Office," No. 8, South-
ampton Buildings, Chancery Lane, in the County of Middlesex, Con-
sulting Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-ninth day of March, in the
year of our Lord One thousand eight hundred and sixty-nine, in the
thirty-second year of Her reign, did, for Herself, Her heirs and
successors, give and grant unto me, the said William Robert Lake, Her
special licence that I, the said William Robert Lake, my executors,
administrators, and assigns, or such others as I, the said William Robert

page_text: Lake, 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 of
"IMPROVEMENTS IN THE MANUFACTURE OF SODA AND POTASH," upon the
condition (amongst others) that I, the said William Robert Lake, 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 William Robert Lake, 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:-
My Invention consists in an economical process of manufacturing
soda and potash. The process of manufacture is based upon,-
Firstly. The known decomposition of chloride of sodium and chloride
of potassium by the oxide of lead in the presence of water at the ordinary
temperature. By this decomposition is formed on the one hand an
oxichloride of load, or more correctly speaking a mixture of chloride
of lead and hydrate of oxide of lead (solid), and on the other hand
caustic potash or soda which remains in solution. This solution
separated from the solid part is evaporated to withdraw from it the
soda or potash.
Secondly. The addition of lime which produces a remarkable increase
in the production of potash and soda hitherto unknown.
Thirdly. The action of lime or any other analagous earth or alkali
in water at various temperatures on the oxichloride of lead or the
mixture of chloride of lead, and the hydrated oxide of lead resulting
from the first operation, for bringing the one or the other into the con-
dition of oxide of lead suitable for recommencing a fresh reaction
upon the chloride of sodium or potassium. In this operation chloride
of calcium is formed in solution in the liquid, which is separated and
thrown away.

page_text: Fourthly. Upon the combination of these two reactions, which may be
continued indefinitely, so that the same oxide of lead may theoretically
decompose an indefinite number of fresh quantities of chloride of
sodium or potassuim, furnishing therefrom the soda or potash. The
only expense for material incurred is that of the chloride of sodium or
of potassium, the lime, and fuel.
I will now describe the manner of proceeding for the manufacture of
soda according to my system. The same details are applicable to the
production of potash, the chloride of sodium being replaced by that of
potassium.
The first operation is as follows:-I pulverize as completely as possible
a quantity of litharge. The manner in which this is effected greatly
influences the quantity of the soda produced. To this litharge is added
water, lime slaked or well pulverized, and sea salt. The mixture is
stirred or ground for some time at the ordinary temperature, and becomes
quite white, at this moment the reaction is finished. The proportions
of the different substances may be varied, but the following have pro-
duced good results:-To a hundred parts by weight of litharge I add
from twenty-five to fifty of lime. In producing soda the quantity of
water appears to be immaterial within certain limits, but it is obviously
advantageous to employ as little as possible, so as to have a liquid more
strongly alkaline and to have as little water as possible to evaporate.
With from once or twice the weight of the litharge, that is to say, from
one hundred to two hundred parts a paste may be formed which will be
easy to stir with an implement or grind in a mill, or in any other way con-
sidered most desirable to effect a complete admixture. Various quantities
of salt may be used without inconvenience. A quantity I often employ
is that which is found in calculating how much salt is necessary to
saturate entirely the water used, and increasing this quantity by the
amount of salt which shall be decomposed in the process, the total being
put in the mixing or grinding apparatus at the starting of the operation.
When the operation is finished there will be found in the liquid a
quantity of soda equal on an average to ten per cent. of the weight of
the litharge used; there will be more or less according to the quality of
the materials and the degree of perfection of the work.
of soda correspond to about thirteen parts of hydrate
the addition of the lime the production of soda is four
The reason of this is probably that chloride of lead is nearly insolable
These ten parts
of soda; without
or five times less.

page_text: in the lime water while it is slightly soluble in pure water, and this
insolubility, which is occasioned by the presence of the lime, prevents
to some extent its being attacked by the soda already formed, which
converts it into hydrated oxide of lead in reproducing chloride of sodium.
This counter action operating at the expense of the soda already
produced it will be understood that with the above mentioned use of the
lime there will be found a much larger quantity of soda. This implies
that the oxichloride of lead, the result of the operation, is not by any
means a compound with definite proportions, but a simple mixture with
variable quantities of chloride of lead and of hydrated oxide of lead.
This fact is also confirmed by other experiments. Whatever else may
be the value of this theory the new fact which I make known certainly
exists, namely, that the addition of lime in the reaction of sea salt
upon oxide of lead gives a considerably superior production of soda.
When the operation is finished the soda liquid is withdrawn from the
paste by filtration, washing, or otherwise. By this means I obtain a
liquid charged with soda containing also a certain quantity of sea salt,
and a small quantity of lime and oxide of lead all in solution. By
properly conducted evaporation I withdraw successively these various
substances to make them re-enter into the following operation, and I
obtain therefrom a definite quantity of pure hydrate of soda, which
only becomes solid after total evaporation.
In the second operation the paste remaining after being well washed
to separate as much of the soda as practicable is put in a vat with a
proper quantity of water and is made to boil during about six or eight
hours. The lime remaining in this paste reacts, as has been said, upon
the chloride of lead and the hydrated oxide of lead, and brings them
to the condition of oxide of lead suitable for further reaction upon the
sea salt, while it forms on the other hand chloride of calcium. When
the boiling is finished it is allowed to deposit. The deposit is effected
very rapidly, and without allowing it to cool I decant the clear liquid
which I put on one side. I then perform a second washing the water
of which is also put aside. The first water withdrawn presents the
following phenomenon :-In proportion as it cools the chloride of
calcium reacts upon the oxide of lead which it holds in solution, and
the chloride of lead and lime will be seen to precipitate in numerous
flakes; this precipitate is withdrawn by decantation to make it re-enter
into the next operation of regeneration, the liquid poured off is mixed
with the washing water, and it is now desirable to withdraw from this

page_text: solution all the oxide of lead which it retains to prevent the loss of any
oxide of lead. I now proceed as follows:-I pour gently and with
constant agitation hydrochloric acid up to the moment when the test
paper gives its first indication of acid; at this instant the liquid
has become perfectly limpid, and only contains chloride of lead and
chloride of calcium; I then pour with constant agitation lime water
till the test paper gives a slight alkaline indication; the insolubility
herein-before mentioned of the chloride of lead in lime water causes
the precipitation of all this chloride. This is withdrawn by decantation
to make it re-enter into the first operation of regeneration, and the
liquid, which no longer contains anything but chloride of calcium is
without value and may be thrown away. The oxide of lead regenerated
in the above operation is employed in a fresh operation of sodification
with the quantities mentioned of water and sea salt. I add besides a
quantity of lime equal to that carried off in solution by the washings
plus the quantity transformed into chloride of calcium. This series of
operations may be renewed indefinitely and will furnish each time the
quantities of soda indicated.
The third operation is the calcination. In all the preceeding operations
it is well to avoid as much as possible the contact of air. The carbonic
acid contained therein is strongly attacted by the soda, the lime, and
the oxide of lead. It is fixed definitely by the lime, but the carbonate
of lime thus formed is injurious, for on the one hand it will no longer
act as caustic lime, and on the other hand it envelopes the grains of
oxide of lead and prevents their reaction upon the sea salt. Never-
theless it would be very difficult for any length of time to guard entirely
against this accidental result. It is therefore desirable from time to
time to proceed with the ejection of this carbonic acid, which I perform
in the following manner :-I take the paste at the moment when it
comes from the operation of regeneration, and when in consequence it
contains no chloride of lead, but only oxide of lead, hydrate of lead,
lime, and carbonate of lime; it is then calcined at a red heat for at least
three hours. Though the oxide of lead is fused the paste will not run
because of the quantity of lime that it contains, so that the operation is
rendered very easy. The paste then becomes bard, compact, and of a
greenish yellow colour, and the carbonic acid is driven off. It must then
be ground completely till it re-assumes a clear green yellow colour; a
little water assists the grinding. It is then ready to be used in the

page_text: operation of sodification. When the paste has been subjected to this
calcination it is more concrete and serves better for the filtration and
washing. The separation of the lead in the soda can be effected by the
use of sulphide of sodium, carbonate of soda, or oxide of calcium in its
various states, also by roasting gently the residue of the evaporation of
the soda liquor and re-dissolving it in a little water. The separation of
the soda from the salt is effected after having taken out of the con-
centrating pan or other vessel as much salt as it will yield, and obtained
nearly all the soda back which this salt contains by exposing it to steam
in a revoling drum of wire gauze or other appliance. I sometimes con-
centrate the liquor by the usual method until it sets in cooling. I remelt
this material either in a little water in the open air or in a current of
steam, and the liquid thus obtained is then definitely evaporated to the
state of hydrate of soda, the residue of this re-dissolving process being
mixed in the first liquid to be evaporated for soda. This operation may
be repeated as often as desirable to obtain a caustic soda of high strength.
I sometimes use mechanical means, such as centrifugal force or pressure.
In the process of regeneration I sometimes instead of boiling the magma
or lead precipitate as it comes out of the washings which have deprived
it of all the soda, wash it several times more, and after having then
boiled it for some time I throw away the water and put in fresh; or I use
boiling lime water, to which the magma is added slowly, and during
which operation the water may be changed from time to time as required;
or I agitate the magma with cold water and lime during some time,
taking the first water away before boiling it, and this operation may so
completely regenerate the chloride of lead that it may suffice to roast or
furnace the stuff in order to decompose the remaining hydrate of lead
before taking it back to the mill without any further boiling.
In witness whereof, I, the said William Robert Lake, have here-
unto set my hand and seal, this Twenty-eighth day of September,
in the year of our Lord One thousand eight hundred and sixty-
WILLIAM ROBERT LAKE. (L.S.)