IMPROVEMENTS IN THE MANUFACTURE OF THE SALTS, CARBONATES, AND HYDRATES OF BARYTA AND STRONTIA, AND ALSO FOR IMPROVED MODES OF MAKING BARYTA AND STRONTIA CAUSTIC
Year: 1873

page_text: PROVISIONAL SPECIFICATION left by Edward Thomas Hughes at the
Office of the Commissioners of Patents, with his Petition, on. the
13th September 1873.-A communication from abroad by Louis
Gustave Ghilain Daudenart and Edmond Verbert, of 34, Rue du
Progrès, Schaerbeek, Brussels.
I, EDWARD THOMAS HUGHES, of the Firm of Hughes and Son, Patent
Agents, 123, Chancery Lane, London, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN THE MANUFACTURE OF THE SALTS,
CARBONATES, AND HYDRATES OF BARYTA AND STRONTIA, AND ALSO FOR IMPROVED
MODES OF MAKING BARYTA AND STRONTIA CAUSTIC," a communication to me
from abroad by Louis Gustave Ghilain Daudenart and Edmond Verbert,
of 34, Rue du Progrès, Schaerbeek, Brussels, to be as follows:—
In order to produce the carbonates of baryta and strontia according to
our process we take alkaline earthy chlorides not only because they are
very soluble and that sulphates of baryta and strontia are obtained from
them with facility and economy, but also that by means of our process
we obtain free hydrochloric acid at the same time that the carbonates of
the alkaline earths are produced,

page_text: The reactions which take place are explained by the following
equations made with regard to the obtaining of carbonate of baryta,
and the equations are the same for carbonate strontia, it being only
necessary to take chloride of strontium instead of chloride of barium :-
The chlorides of barium and strontium whether obtained by one of the
following ordinary methods, first, by the action of hydrochloric acid on
the carbonates of baryta and strontia in their natural state; secondly, by
the action of the same acid on the sulphurets of barium and strontium
procured by the decomposition of the sulphates of these bases by carbon;
thirdly, by the reciprocal action, indicated by Monsieur Kuhlmann,
between the sulphates of baryta or strontia carbon and the chloride of
manganese, or by any other method by which they are. dissolved in water
to 12 or 15 degrees Baumé. The solution thus obtained whether the
chloride of barium or the chloride of strontium is mixed with hydrate of
magnesia in any suitable apparatus which can be afterwards colosed.
This mixture is kept in continual agitation in the closed apparatus and
subjected to the action of a current of carbonic acid, which gas is
absorbed by the magnesia forming a carbonate of this base.
In principle the carbonate of magnesia decomposes the alkaline earthy
chlorides, but the employment of an excess of carbonic acid causes the
decomposition to be more rapid, and at the same time the oarbonates of
the alkaline earths are obtained, especially those of baryta and strontia,
free from carbonate of magnesia, a result that cannot be obtained by the
mixture of the chlorides with the carbonate of magnesia only. This
carbonate dissolves in water, assisted by an excess of carbonic acid, and
'thus a bi-carbonate of magnesia is formed, and besides this, a double
decomposition rapidly takes place between the alkaline earthy.chlorides
and the bi-carbonate of magnesia, carbonate of baryta is precipitated, the
carbonic acid is regenerated and the liquor holds in solution chloride of
magnesium as expressed by the following notation :--
Carbonate of magnesia being but little soluble in carbonic acid,
or in

page_text: other words, the solubility in water of the bi-carbonate of magnesia
being feeble it was conceived that the current of carbonic acid should
be made to pass for a much longer time than would be required for the
simple carbonation of magnesia.
It is evident that the carbonation can be effected in any special or
distinct apparatus, and variations of minor importance may be made in
the manipulation, but I prefer the process before described on account
of its simplicity.
In practice the treatment of the alkaline earthy chlorides by magnesia
and carbonic acid should consist of two operations.
In the first the magnesia is in excess, which gives, when the reaction
is terminated, a liquor containing exclusively chloride of magnesium
which is decanted, and a precipitate obtained consisting of a carbonate
of the alkaline earth and the magnesia employed in excess in a car-
bonated state.
In the second operation an excess of alkaline earthy chloride is poured
on the precipitate, that is, a quantity of the chloride equal to that
previously used, augmented by a little in addition to what is necessary
for the neutralization of the excess of the carbonate of magnesia.
By the action of the carbonic acid the excess of the carbonate of
magnesia is transformed into chloride of magnesium and is replaced in
the precipitate by an equivalent quantity of carbonate alkaline earth,
the final result being carbonate of baryta or strontia which is obtained
in a pure state after a series of washings. The liquor after this second
5 operation is a mixture of chloride of magnesium and of alkaline earthy
chloride, the latter being in excess should be again used as it is superior
to that employed in the first operation, and by means of known reagents
and tests it is to be ascertained, first, that the liquor of the alkaline
earthy chloride employed the first time contains only chloride of
) magnesium when the reaction has terminated, and secondly, that the
precipitate after the second operation washed and dissolved in hydro-
chloric acid does not contain any magnesia.
The liquors which only contain chloride of magnesium are con-
centrated by evaporation to 44 or more degrees Baumé, and are then
5 passed into the crystallizers, or, if allowed to cool, they become hard
masses which are broken in pieces to remove them, and, as will be seen,

page_text: It is of importance to remark that the hydrated chloride of magnesium
calcined at a low red heat in a reverbatory furnace or in crucibles is not
completely decomposed; one-fifth escapes decomposition by the simple
disengagement of a part of the water it contains, besides all the
magnesia formed and submitted in this operation to a heat above
300 degrees centigrade, is when cold in an unfavorable condition for
absorbing carbonic acid, and it is hydrated with such slowness as to be
incompatible with a rapid revivification of the carbonate of magnesia,
and it is upon the revivification that the whole of my manufacture is
based.
Hydrated chloride of magnesium submitted to the action of a current
of steam superheated to about 300 degrees centigrade without pressure,
becomes completely decomposed and is in the condition to be rapidly
hydrated and carbonated.
To manufacture caustic baryta and strontia from their carbonates by
our process we mix the carbonate of baryta or strontia with carbon or
chalk, and heat the mixture, whether subjected to the action of super-
heated steam or not, in a regenerating or reverbatory furnace, which
process is applicable, not only to the carbonates of baryta and strontia
manufactured as before described, but also to the carbonates of baryta
and strontia in their natural state or produced in any other way, and I
also employ the furnaces for the decomposition of all salts that require
a high temperature, especially the sulphates of baryta and strontia
mixed with carbon. By these means we obtain such a temperature
that the carbonates of baryta and strontia whether mixed with carbon
or submitted to the action of superheated steam are rapidly decomposed
with great facility and therefore economically.