Improvements in the Manufacture of Caustic or Carbonated Soda and Caustic Potash.
Year: 1887

page_text: Date of Application, 23rd Mar.. 1887
Complete Left, 23rd Dec., 1887
Complete Accepted, 9th Mar., 1888
Improvements in the Manufacture of Caustic or Carbonated Soda
and Caustic Potash.
1, ALPHONSE DELHAYE of 86 Rue Royale, Brussels in the Kingdom of Belgium
Doctor of Medicine do hereby declare the nature of this invention to be as
follows:-
This process is based on the preparation of phosphate of soda either by decomposing
sea salt with phosphoric acid, or by precipitating a well concentrated solution of
phosphate acid of calcium by sulphate of soda and the precipitation by means of milk
of line of this saline solution, to which is added or not the required quantity of
carbonate of soda to obtain bibasic phosphate of soda all as hereafter described.
A: If sea salt is employed the phosphated mineral is mixed with a sufficient
quantity of Hydrochloric acid to dissolve the whole of the phosphoric acid. The
reaction having taken place a sufficient quantity of sulphuric acid is added to com-
bine with all the dissolved lime. It precipitates sulphate of lime, then it is filtered.
The cake after being washed, is dried, the filtered liquor is a solution of hydrochloric
acid and of phosphoric acid with a small quantity of sulphate of lime. It is used
several times afterwards instead of hydrochloric acid to dissolve new portions of
mineral until it contains 15 to 17% of phosphoric acid. Then it is put in contact
with chloride of sodium sufficient to produce by decomposition acid phosphate of
sodium and it is heated until reaction ceases. The hydrochloric acid which is
disengaged or produced is collected by condensation.
Instead of the thus prepared hydrochlorphosphoric liquor acting on the chloride of
sodium, phosphoric acid prepared by the direct action of sulphuric acid on the
mineral phosphate may be used.
B: If sulphate of soda is employed the finely pulverized mineral is mixed with a
certain quantity of sulphuric acid of 53° calculated to obiain after decomposition acid
phosphate of lime. The mass is quickly stirred until reaction has ceased then sulphate
of soda is added sufficient to obtain by double decomposition sulphate of lime and
acid phosphate of soda (Pho) 2 H (a + So na So' Ca + (Pho) H Na² it is
then filtered, the cake is then washed, dried and pulverized.
=

page_text: The filtered liquor is a solution of acid phosphate of sodium.
The acid phosphate so obtained is employed in the manufacture of soda of any kind
or after addition of a proportion of carbonate of soda sufficient to obtain bisodic
phosphate.. In this case the solution of phosphate of soda is treated with milk of
lime stirring until complete decomposition takes place when it is filtered; after com-
plete precipitation the cake is dried and pulverized, and the result is assimilable
phosphate of lime.
The liquid resulting from filtration is a solution of caustic soda which is evaporated
if it is desired to obtain soda which after treatment is evaporated by a current of
carbonic acid in excess if it is desired to obtain carbonate of soda.
What has been said with regard to soda is applicable in the preparation of caustic
potash.
BREWER & SON,
For the Applicant.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Caustic or Carbonated Soda
and Caustic Potash.
1, ALPHONSE DELHAYE, of 86 Rue Royale, Brussels, in the Kingdom of Belgium
Doctor of Medicine do hereby declare the nature of this invention and in what manner
the same is to be performed to be particularly described and ascertained in and by the
following statement :-
This proesss is based on the correlative preparation of precipitated phosphate and
of soda. It consists in the precipitation by means of milk of lime of phosphate of
soda prepared by the decomposition of sea salt by means of hydro-chloric phosphoric
acid or by the decomposition of acid phosphate of lime by means of sulphate of
soda.
DESCRIPTION.
A. If sea salt is used it may be used with any sort of phosphate and even with the
so called scoria "Thomas."
After pulverization it is intimately mixed with hydrochloric acid diluted to a third
in a mechanical mixer, in this manner all the phosphate which is found in the mineral
is dissolved and the result is acid phosphate of lime and chloride of calcium.
(Pot) 2 ca 3 + H cl
=
(Po) 2 ca H4 + 2 Ca cl².
It is filtered; the cake, after washing is thrown out: it is sand, clay, organic
materials etc. The filtered liquor is treated with sulphuric acid at 60° Beaumé in
quantity calculated for precipitating all the lime, it forms a fine precipitate of sulphate
of lime.
It is filtered-The liquid which filters is hydrochloric phosphoric solution.

page_text: The cake being washed and dried is plaster of superior quality-(Po¹) Ca H + 2
ca cl² 3 So H2 = 3 Soca + 2 (Po' H³, 2 H cl) hydro-chloric phosphoric acid.
The hydro-chloric phosphoric solution serves for several operations instead and in
place of hydrochloric acid to attack new portions of phosphate until concentration of
the liquid into phosphoric acid (15 to 17%).
This series of operations presents immense advantages over the extraction by means
of sulphuric acid of the phosphoric acid of phosphates.
1°. It is excessively rapid.
20. It removes all phosphoric acid. Without expensive working up and not taking
a long time.
3°. It precipitates sulphate of lime in a form suitable for all industrial uses which
is not the case with sulphate of lime produced by the direct action of sulphuric acid
on the phosphate; in which case being mixed with phosphate foreign matters it is no
longer suitable to these uses.
40. It does not leave in the liquid free sulphuric acid in excess such as that which is
met with in great quantity in the phosphoric acid of commerce. This liquid hydro-
chloric phosphoric acid is put together with chloride of sodium in a sulphate furnace
and the temperature is raised to 200° which is maintained as long as it gives off dis-
engaged hydrochloric vapours, the mass when dried is monosodic phosphate which is
dissolved in 3 times its weight of boiling water. The employment of this acid
liquid to decompose sea salt, presents great advantages over the use of ordinary
phosphoric acid for the same effect.
10. The absence of sulphuric acid suppresses the sulphate of soda in the sodic
phosphate residue of the operation: in fact sulphuric acid forms with the sea salt
sulphate of soda, as is the case with ordinary phosphoric acid, which contains much
sulphate acid.
20. The reaction is complete and more rapid, the presence of hydrochloric acid by
giving off acid vapours causes the mass to boil, thus starting the acid vapours which
are to be produced by decomposition of salt and facilitates the re-action when phos-
phoric acid alone is used the mass becomes hard and vitreous in spite of working and
decomposition is with difficulty completed. The preparation of the phosphoric acid,
and the decomposition of salt by the latter differs then essentially from the operations
above described-the result of this method is eminently more favourable. B. If
sulphate of soda is used.
The phosphate being pulverized is mixed with sulphuric acid at 45° Beaumé, in
quantity calculated to obtain acid phosphate of lime the mixture is made in a cast iron
vessel heated in a sand bath, the temperature of which can be varied or raised to,
from 180° to 200° and intimately mixed by means of a mechanically driven rapid
mixing machine; there is added as soon as the mixture becomes homogeneous, a
quantity of sulphate of soda sufficient to precipitate all the lime of acid phosphate;
the mixing up is continued until the mass is completely dried. The temperature which
at first is only 100° increases in proportion or in accordance with the drying of the
mixture, and then attains the heat of 200° necessary for rapidly completing the
extraction of the phosphoric acid.
In this manner in proportion or in accordance with the decomposition of tri-basic
into mono-basic, the latter is found in presence of sulphate of soda which decomposes
it. (Po) Ca + 2 So' H² (Po) Ca H + 2 So Ca-(decomposition of phos-
phate into monobasic) (Po) 2 Ca H4 + So 4 Na²
=
So Ca 2 Po' Na H
(decomposition of monobasic phosphate of lime into monobasic phosphate of soda).
When the mass is well dried water is added by degrees until it is brought to a
thick pulpy mass, this is maintained to ebullition for 15 minutes then enough water is
added to give to the pulpy mass the necessary degree of liquidness.
It is filtered, the cake is sulphate of lime mixed with impurities. The liquid of the
filtration is a solution of phosphate of soda.
C. The solution of the phosphate of soda being added or not with a quantity of
carbonate of soda sufficient to take bisodic phosphate is mixed with milk of lime in
proportion calculated to precipitate all the free and combined phosphoric acid.

page_text: A current of steam is made to pass through it which raises the temperature to 80°
to 100° and at the same time the mixture internally stirred. These bodies or matters
are left for two hours. The re-action is only complete when a part of the filtered and
acidulated liquid no longer precipitates by the molybdate of ammonia, it is then
filtered; the cake is precipitate of bibasic calcium phosphate soluble in citrate of
ammonia. The liquor being filtered is a solution of caustic soda, which is employed
if it is desired to have caustic soda, which is or may be evaporated after treatment
by carbonic acid if it is desired to have carbonated soda. All that has been said
for soda is applicable to the manufacture of potash; instead of the sulphate of soda
and the chloride of sodium, sulphate of potash and chloride of potassium may be
used.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is:
1. The preparation of phosphate precipitated and of soda or of potash by the
method above described.
2. The decomposition of sea salt by hydro-chloric phosphoric liquid produced by
the treatment of phosphates by means of hydrochloric acid and sulphuric acid in the
conditions above described.
3. The decomposision at a temperature progressively increasing but not exceeding
200 degrees of acid phosphate of lime by means of sulphate of soda.
4. The manufacture of caustic or carbonated soda and caustic potash and of
phosphate of soda or potash substantially as hereinbefore described.
Dated this 23rd day of December 1887.