Process for the Manufacture of Neutral Sodium Carbonate, Neutral Sodium Sulphite and Sodium Borates.
Year: 1894

page_text: COMPLETE SPECIFICATION.
Process for the Manufacture of Neutral Sodium Carbonate, Neutral
Sodium Sulphite and Sodium Borates.
We, EMIL DRESEL and JULIUS LENNHOFF both of Dresdenerstrasse 40, in
the City of Berlin, in the Empire of Germany, Chemical Manufacturers, do
hereby declare the nature of our said invention and in what manner the same
is to be performed, to be particularly described and ascertained in and by the
following statement :-
The present invention has for its object the manufacture of neutral sodinm
carbonate, neutral sodium sulphite and sodium borates directly from sodium
chloride, and consists in converting a solution of sodium chloride by means of an
equivalent of neutral ammonium carbonate, neutral ammonium sulphite or neutral
ammonium borate or biborate respectively, into ammonium chloride and the corre-
sponding salt of sodium. From the solution containing both products of the
reaction the sodium salt is precipitated by passing ammonia in the gaseous state
and under cooling through the liquid so long until no further precipitate takes
place.
The cooling must be all the stronger according to the stronger alkalinity of the
salt to be produced, in order to exclude secondary reactions, between the sodium
salt formed and the ammonium chloride.
These secondary reactions are brought about partly by the increased alkalinity
of the dissolving agent over and above that of the corresponding sodium salt
owing partly to a too rapid absorption of ammonia and partly to a decreased
tenperature.
It consequently follows that the decrease of the temperature must be very great
for the preparation of sodium monocarbonate (from 5°-8° C.); for the preparation
of sodium monosulphite it can be less (about 15° C.) and still less for the prepara-
tion of sodium biborate (20°-22° C.), whereas it must be correspondingly greater
for the preparation of neutral sodium borate (12° C.). In these cases the cooling
can be substituted-although for practical purpose it is not so advantageous—by
passing in the ammonia under pressure, whereby the height of the pressure must be
regulated according to the stronger or weaker alkalinity of the salt to be
produced.
In both procedures the solvent action of the water present on the ammonium
chloride is considerably increased, whereas the capability for dissolving the sodium
salt is so weakened, that the latter is almost entirely precipitated, while the whole
quantity of the ammonium chloride remains in solution.
The manufacture of neutral sodium carbonate and neutral sodium sulphite
respectively is carried out most preferably in such manner, that one equivalent of
carbon dioxide or sulphur dioxide respectively is passed into an ammoniacal
solution of sodium chloride, then dry ammonia gas under cooling and under a
pressure of about 1 lbs. per square inch, is passed into the liquid until no further
precipitate takes place, care being taken that for the preparation of the carbonate
the temperature of the liquid does not rise higher than 5°-8° C. and for the
preparation of the sulphite not higher than 15° C. The neutral sodium sulphite
is precipitated as an anhydrous salt, whereas the sodium inonocarbonate is
precipitated in combination with one molecule of water, which can be easily
expelled by heating to above 100° C.
It will be evident that the solution of sodium chloride can be directly saturated
with the excess of ammonia required for the precipitation, although such a
procedure is less advantageous.

page_text: For the manufacture of borates both sodium chloride and sodium sulphate can be
taken as an initial product by treating them with ammonium borate and ammonia.
The ammonium borates are applied either in the form of the ready salts (for
instance by dissolving or suspending in water according to the borate to be
produced one or two equivalents of boric acid and passing ammonia into the
Liquid) and those are treated with a solution of sodium chloride or sulphate, or the
ammonium borate is obtained in the solution of sodium chloride itself which is to
be decomposed, by rendering the latter ammoniacal and adding boric acid to the
same in a quantity of one to two equivalents.
The following method of working has been found to be most preferable:
One or two equivalents of boric acid are brought into a solution of sodium
chloride or sulphate according as it is desired to obtain neutral borate or biborate
(borax) and dry ammonia gas is passed into the solution. A rise of temperature
results, whereby the boric acid is dissolved and combined with the ammonia to
ammonium burate, the latter converting the sodium salt into sodium borate and
ammonium chloride or sulphate respectively. On cooling the borate crystallizes
out, which is separated from the solution of the ammonia salt in the usual
manner.
Since the sodium borates of an alkaline reaction effect the decomposition of the
ammonia salts, it is advisable to use ammonia in excess, until the solution possesses
the same alkalinity as the horate to be produced. Complete decomposition of the
reagents employed is thereby effected.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what
we claim is :-
1. Process for the manufacture of neutral sodium carbonate, nentral sodium
sulphite, and sodium borates directly from sodium chloride, characterized by the
conversion of sodium chloride according to the sodium salt to be produced with an
equivalent of neutral ammonium carbonate, neutral ammonium sulphite or
ammonium borate, and the precipitation of the sodium salt formed from the
solution of the products of the reaction by passing ammonia under cooling or
pressure or both, which is to be applied all the stronger according to the stronger
alkalinity of the salt to be produced substantially as described.
2. A modification of the process for manufacturing sodium borates as claimed in
Claim 1, in which sodium sulphate is employed as an initial product in the place of
sodium chloride substantially as described.
3. A modification of the process for manufacturing sodium borates as claimed in
Claim 1, in which ammonium borates are employed either in the form of the ready
salts, or in which boric acid and ammonia are used for the preparation and
precipitation of the borates during the process itself, substantially as described.
4. A modification of the process for the manufacture of sodium borates as
described in Claims 1, 2 and 3 in which, for the purpose of preventing secondary
reactions, ammonia is used in such an excess that the solution possesses the same
alkalinity as the products to be prepared, substantially as described.
Dated the 3rd day of August 1894.
PHILIP M. JUSTICE,
Filing Agent.