IMPROVEMENTS IN THE MANUFACTURE of SODA, AND IN THE REGENERATION OF VARIOUS AGENTS USED THEREIN, PARTLY APPLICABLE ALSO TO THE MANUFACTURE OF POTASH
Year: 1882

page_text: LETTERS PATENT to Walter Weldon, of Rede Hall, Burstow, in the County
of Surrey, for an Invention of "IMPROVEMENTS IN THE MANUFACTURE of
SODA, AND IN THE REGENERATION OF VARIOUS AGENTS USED THEREIN,
PARTLY APPLICABLE ALSO TO THE MANUFACTURE OF POTASH." A communi-
cation from abroad by Dr. Max Schaffner and Wilhelm Helbig, both of Aussig,
in the Empire of Austria.
PROVISIONAL SPECIFICATION left by the said Walter Weldon at the
"IMPROVE-
Office of the Commissioners of Patents on the 9th January 1882.
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey.
MENTS IN THE MANUFACTURE OF SODA, AND IN THE REGENERATION OF VARIOUS
AGENTS USED THEREIN, PARTLY APPLICABLE ALSO TO THE MANUFACTURE OF
POTASH." A communication from abroad by Dr. Max Schaffner and Wilhelm
Helbig, both of Aussig, in the Empire of Austria.
Sodn is at present manufactured by two processes, respectively known as the
Leblanc process and the ammonia process. In the Leblanc process sulphuric acid
is used, such sulphuric acid being usually manufactured for the purpose from the
sulphur of pyrites. The sulphur so employed serves only once, and is then thrown
away in combination with calcium as what is known as tank-waste. This residue
accumulates in immense quantities in the neighbourhood of Leblanc soda-works,
and gives off continually both liquid and gaseous products, extremely deleterious
both to the atmosphere and to the water-courses. In the ammonia process sulphur
is not used, but its residual product is ammonic chloride, from which ammonia for
use again is regenerated by distillation with lime. The Leblanc process and the
ammonia process have not hitherto been employed in combination; but each
has been practised hitherto only separately and distinctly the one from the
other.
The first part of the present Invention consists in combining the Leblanc
process with the ammonia process so as to effect a very considerable economy in

page_text: both, by employing for the regeneration of ammonia from the ammonium chloride
produced in the ammonia process the magnesia obtained by the reaction of
magnesium chloride upon the tank-waste of the Leblanc process, and then
employing the magnesium chloride resulting from the reaction of the said
magnesia upon the said ammonium chloride for the decomposition of a further
quantity of tank-waste from the Leblanc process. The first mentioned reaction
takes place according to the equation
2 (NH, Cl) + Mg O = 2 NH, 0 + Mg Cl,
and the second reaction takes place according to the equation
Ca SH. O + Mg Cl₁ = Ca Cl₂ + Mg O + H, S.
By combining these two reactions one can thus completely avoid the consumption
of the lime at present employed for the decomposition of the aminonium chloride
of the ammonia process, and can at the same time avoid the immense loss and
intolerable nuisance caused by the vast quantities of sulphur employed in the
Leblanc process having to be thrown away as tank-waste after having been used
only once, since the said combination of reactions enables the sulphur employed
in the Leblanc process to be continually regenerated and used over and over again
indefinitely.
The second part of this Invention consists in employing the sulphuretted
hydrogen obtained by decomposing tank-waste by solution of magnesium chloride,
whether the said solution of magnesium chloride be obtained as above or otherwise,
for the direct production of sulphuric acid, by burning the sulphuretted hydrogen
into sulphurous acid, and then employing the resulting sulphurous acid in vitriol
chambers, as will be well understood.
The third part of the present Invention consists in obtaining free sulphur from
sulphuretted hydrogen produced as above described, by burning one-third of the
said sulphuretted hydrogen into sulphurous acid, then mixing the sulphurous acid
so obtained with the other two-thirds of the sulphretted hydrogen, and then
causing the gases so mixed to react upon each other in presence of and in contact
with a solution of a metallic chloride, and more especially of either calcium chloride
or magnesium chloride.
The fourth part of the present Invention consists in applying the first three
parts of it to the tank-waste produced in the manufacture of potash by the
Leblanc process.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Walter Weldon in the Great Seal Patent Office on the 27th June
1882.
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey. " IMPROVE-
MENTS IN THE MANUFACTURE OF SODA, AND IN THE REGENERATION OF VARIOUS
AGENTS USED THEREIN, PARTLY APPLICABLE ALSO TO THE MANUFACTURE OF
POTASHI." A communication from Dr. Max Schaffuer and Wilhelm Helbig, both
of Aussig, in the Empire of Austria.
"
Soda is at present manufactured by two processes, respectively known as the
Leblanc process and the ammonia process. Sulphur is used in the Leblanc process,
and after having been employed only once is thrown away, in combination with
calcium, as what is known as "tank-waste," vat-waste," or "alkali-waste." In
the ammonia process sulphur is not used. The residue of that process is chloride
of ammonium, from which ammonia is regenerated for use again by distillation
with lime. The Leblanc process and the ammonia process have always hitherto
been practised separately and distinctly the one from the other.
The present Invention consists in combining the Leblanc process with the
ammonia process, by employing for the regeneration of ammonia from the chloride
of ammonium of the latter process hydrated magnesia precipitated by the reaction
upon chloride of magnesium in solution in water of the calcium sulphide contained
in the tank-waste which is the residue of the Leblanc process, and then employing
the magnesium chloride resulting from the reaction of the said magnesia upon the
said ammonium chloride for the decomposition of a further quantity of tank-waste
from the Leblanc process. The first-mentioned reaction takes place according to
the equation:
2(NH, C1) + Mg H, O, = ?NH, O + Mg Cl, + H, O,
and the second reaction takes place according to the equation:
Mg Cl₂+ CaS + 2 H, O
=
Ca Cl,+Mg H₂O₂ + H, S.
By combining these two reactions there is obtained a new industrial result of great
importance. For the lime hitherto and at present used in the ammonia process is
substituted perpetually regenerated hydrate of magnesia, obtained as a bye-product
of the operation of decomposing, in such wise as to liberate its sulphur, the tank-
waste of the Leblanc process; and the whole of that part of the sulphur used in the
Leblanc process which exists in the residue of the Leblanc process in the state of
sulphide of calcium is liberated as sulphuretted hydrogen; which sulphuretted
hydrogen can either be wholly burnt into sulphurous acid, which can be then
converted into sulphuric acid, as will be well understood, or can be treated for the
obtainment of its sulphur in the free state, according to the Invention protected
by the Letters Patent numbered 955 of the year 1878, or can be utilized in any
other manner which may be preferred.
What my correspondents believe to be the best manner of employing the
chloride of magnesium, obtained as above described, for the liberation of sulphur
from the tank-waste of the Leblanc process, is that of heating together the solution
of magnesium chloride and the tank-waste, in a closed vessel, furnished with a
mechanical agitator, as described in the Specification of the Patent No. 955 of
1878 aforesaid. It will be desirable, however, in order to diminish loss of chloride

page_text: of magnesium, to divide the operation into two stages. The first stage should
consist in heating the tank-waste with an excess of solution of chloride of
magnesium, and then, when the calcium sulphide in the tank-waste has been
completely decomposed, separating the resulting magnesia, either by subsidence
and decantation, or by filtration. The magnesia so separated will then be ready
for use for decomposing an equivalent of chloride of ammonium from the ammonia
process. The liquor separated from the magnesia will be a mixed solution of
calcium and magnesium chlorides, and this should now be heated with a quantity
of tank-waste containing more calcium sulphide than the quantity equivalent to
the magnesium chloride in the said mixed solution. When the whole of the
magnesium chloride in the said mixed solution has been decomposed by a portion
of the calcium sulphide in the excess of tank-waste with which it has thus been
heated, a second filtration, or a second operation of subsidence and decantation,
should be performed. The solution separated by this second operation of filtration
or of subsidence and decantation will contain only chloride of calcium, and may be
thrown away, or otherwise disposed of. The solid matter separated from the
solution of calcium chloride will consist partly of hydrate of inagnesia and partly
of excess of undecomposed tank-waste, and should now be treated, with or without
more tank-waste, by an excess of solution of chloride of calcium.
The manner of employing the hydrated magnesia, obtained as aforesaid, for the
decomposition of the chloride of aminonium of the ammonia process, may be the
same as that which is at present followed for decomposing that chloride of
ammonium by lime.
The present Invention is so far applicable to the manufacture of potash that
the tank-waste from which sulphur is liberated as sulphuretted hydrogen by the
reaction upon the tank-waste of chloride of magnesium obtained by decomposing
chloride of ammonium from the ammonia process by hydrate of magnesia obtained
in a preceding operation by the reaction of tank-waste and such chloride of
magnesium upon each other, may be the residue of the manufacture of potash by
the Leblanc process.
Between the present Invention and all preceding proposals for the use of
magnesia for the decomposition of the chloride of ammonium of the ammonia
process, there are essential differences, alike of object, of method, and of results.
All former proposals to decompose by magnesia the chloride of ammonium of the
ammonia process have had for their object the obtainment as hydrochloric acid of
the chlorine of the chloride of sodium converted by that process into soda; but the
object of the present Invention is to obtain, not hydrochloric acid, but sulphuretted
hydrogen. All preceding proposals to use magnesia instead of lime for decom-
posing the chloride of ammonium of the ammonia process have been based on the
iden (which has never yet proved capable of practical realization) of evaporating to
dryness the resulting solution of chloride of magnesium, and then heating the dry
salt in a current of steam, so as to obtain on the one hand bydrochloric acid and on
the other hand anhydrous oxide of magnesium; but by the present Invention the
chloride of magnesium is decomposed by treatment of the solution itself with the
tank-waste of the Leblanc process, and the products obtained, instead of being
anhydrous oxide of magnesium and vapour of hydrochloric acid, are sulphuretted
hydrogen, hydrate of magnesia, and solution of chloride of calcium. Lastly, while
to decompose the chloride of ammonium of the ammonia process by magnesia
obtained by decomposing magnesium chloride by heating it in a current of steam
would be to decompose it by anhydrous oxide of magnesium got by reacting upon
solid chloride of magnesium by heat and a current of vapour, under the present
Invention the agent used for the decomposition of the chloride of ammonium is
hydrate of magnesia, got by treating a solution of chloride of magnesium by solid
sulphide of calcium.
What is claimed as the Invention secured to my correspondents by the herein-
before in part recited Letters Patent is the combination of the Leblanc process with

page_text: the ammonia process, in the manner above described, whereby the chlorine of the
chloride of sodium converted into soda by the ammonia process is made to pass
successively into combination first with magnesium and then with calcium, and
before being thrown away or otherwise disposed of as chloride of calcium is made
to liberate sulphur from the residue of the Leblanc process.
In witness whereof I, the said Walter Weldon, have hereto set my hand
and seal this Twenty third day of June in the year of our Lord One
thousand eight hundred and eighty-two.
WALTER WELDON. (L.S.)