Year: 1894

page_text: Date of Application, 23rd Jan., 1894
Complete Specification Left, 20th Oct., 1894-Accepted, 19th Jan., 1895
I, GEORGE STILLINGFLEET JOHNSON, of 11 Savile Row, W. in the County of
London, Scientific Chemist, and Demonstrator of Chemistry in King's College,
London, do hereby declare the nature of this invention to be as follows:-
(1.) A double salt, consisting of two molecules of sodium sulphite, combined with
one molecule of sodium carbonate, and twenty-one molecules of water, is obtained
in crystals by mixing 7 parts by weight of crystallized sodium sulphite with.
4 parts by weight of crystallized sodium carbonate, dissolving the two salts
together in 12 parts by weight of water, and evaporating the solution by heat,
The
until a film forms on the surface of the liquid whilst it is still hot.
liquid is then cooled and a crystal of the double salt (previously prepared) is
introduced; the new compound then crystallizes out.
(2.) The same double sulphite and carbonate of sodium may also be prepared by
evaporating the solution prepared as above in a vacuum over sulphuric acid.
Deted this 23rd day of January 1894.
I, GEORGE STILLINGFLEET JOHNSON, of 11 Savile Row, W. in the County of
London, Scientific Chemist and Demonstrator of Chemistry in King's College,
London, 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 :-
A. double salt, consisting of two molecules of sodium sulphite, combined with one
molecule of sodium carbonate, and twenty-one molecules of water, is obtained in
crystals by mixing 7 parts by weight of crystallised sodium sulphite with 4 parts
by weight of crystallised sodium carbonate, dissolving the two salts together in
12 parts by weight of water, and evaporating the solution by boiling until a film
forms on the surface of the liquid whilst it is still hot. The liquid is then cooled
and a crystal of the double salt (previously prepared) is introduced; the new
compound then crystallises out.
The same double sulphite and carbonate of sodium may also be prepared by
evaporating the solution of mixed sulphite and carbonate in a vacuum over
sulphuric acid.
As sodium sulphite can be produced by blowing sulphurous acid gas (sulphur
dioxide) through a solution of sodium carbonate according to the equation

page_text: carbonate to form the new double salt, by blowing sulphurous acid gas into a
solution of sodium carbonate according to the equation
carbonate to form the new double salt, by blowing sulphurous acid gas into a
solution of sodium carbonate according to the equation
3 Na,CO, +2 SO2 + 21 H,O= (2 Na₂SO3 Na₂CO₂ 21 H₂O) + 2 CO₂
the new double salt and carbonic anhydride.
In order to effect crystallisation of the new double salt, the concentration of the
solution must be carried farther than is necessary for the crystallisation of either of
the constituent salts, inasmuch as the double salt dissolves in 1-6 times its own
weight of water. The crystallisation is however easy, as the salt is much more
soluble in hot water than in water at the ordinary temperature.
Its crystals do not undergo oxidation on exposure to air at the ordinary
temperature but they gradually lose water becoming opaque.
They part with the whole of their combined water at 100° C., losing 51.35 per
cent. of their weight, no air or oxygen being present. The salt is slightly oxidised
when heated in air at 100° C.
By evaporating the solution of the salt at 60° C., an acicular variety is obtained,
which has the same composition as the salt obtained in the ordinary way, but
retains its water of crystallisation notwithstanding exposure to air.
Solutions of the double salt are very slowly oxidised on exposure to air,
particularly when concentrated, but when diluted to the extent of 1 in 4 parts of
water, they behave like solutions of the mixed salts.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
The manufacture of a double sodium salt consisting of sulphite and carbonate,
substantially as described.
Dated this 20th day of October 1894.
ABEL & IMRAY,
Agents for the Applicant.