IMPROVEMENTS IN THE MANUFACTURE OF SODA AND OF POTASH
Year: 1855

page_text: PROVISIONAL SPECIFICATION left by Frédéric Margueritte at the Office
of the Commissioners of Patents, with his Petition, on the 20th January
1855.
I, FRÉDÉRIC MARGUERITTE, Chemist, of Paris, in the Empire of France,
and of 32, Essex Street, Strand, London, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN THE MANUFACTURE OF SODA AND OF
POTASH" to be as follows, viz. :-
My Invention consists in the application of oxalic and boric acids to
decomposing common salt, or chloride of sodium and chloride of potassium
for extracting soda & potash, and in regenerating said acids by means of
sulphuric, chlorhydric, and carbonic acids. When oxalic acid is acted with in
the case of soda, I mix it in suitable proportions with chloride of sodium, and
by gradually raising this mixture to and keeping it at a gentle heat until no
more chlorhydric acid is evolved, I obtain by such distillation chlorhydric
acid and oxalate of soda. This latter is treated with lime, either after having
dissolved the oxalate, thus yielding a precipitate of oxalate of lime and a solu-
tion of caustic soda; or else the oxalate of soda is treated by forming said
oxalate into a moist paste, which is dried and exposed to carbonic acid, and
the mass thus obtained is lixiviated and converted into carbonate of soda and
oxalate of lime. The oxalate of lime being treated with sulphuric acid forms
sulphate of lime and sets free oxalic acid, which may thus be used over and
over again. Chloride of potassium is treated in a similar manner for extracting
potash.

page_text: When boric acid is operated with, I take the crystallized or hydrated acid
and mix it, in the case of soda, with a suitable quantity of chloride of sodium;
the mixture is calcined in an earthen or iron retort, which is so constructed
that the charge may in a continuous manner be introduced at the top and run
out at the bottom, the same as in a cupola, or smelting.. or..blast,furnace; this
retort is heated in any suitable way. During the operation boric acid and
chlorhydric acid is evolved, and in order to prevent waste these gaseous pro-
ducts are collected in suitable condensers, which are in connexion with the top
part of the furnace retort. When the mixture of boric acid and common salt
has been calcined so that no more chlorhydric acid is evolved, the bottom of
the furnace or retort is opened, and the molten mass is let run out. This
liquefied mass will be found to divide into two distinct strata or layers, one of
which is borate of soda, and the other chloride of sodium that has not been
acted upon, and may be put again in the retort. The borate of soda which is
thus obtained is dissolved and mixed with a sufficient quantity of lime, whence
I obtain a precipitate of borate of lime and of caustic soda, which may be, car-
bonated by any suitable means. The borate. of lime having been washed, the
boric acid may be regenerated from it in two ways; first, by dissolving it hot in
the chlorhydric acid, which is obtained by decomposing the salt; the hot solu-
tion, being sufficiently concentrated, gives off nearly the whole of the boric acid
by cooling down. This acid crystallizes, and the mother water or chloride of
calcium is got rid of by letting it run off, or by squeezing the acid crystals.
Before throwing this mother water away it will be well to add a sniall quantity
of lime, so as to absorb and précipitate, in the form of borate of lime, what little
boric acid there may have escaped crystallization. The other means is by
passing a current of carbonic acid into a liquid, in which the borate of lime is
held in suspension, or otherwise exposing the borate to the action of carbonic
acid in any suitable way. The borate of lime is then divided into carbonate of
lime and boric acid.. When the absorption of carbonic acid ceases, or as soon
as the borate of lime 'has been completely decomposed, 'the mass is-lixiviated
in liot:water; and then by cooling I obtain crystallized boric acid, the residue
consisting of carbonate 'of lime, which may by calcination be converted into
caustic lime and carbonic acid, that may both be used for the following opera-
tions. The chloride of potassium is treated in a similar way with boric acid.
'