Improvements in the Manufacture of Chlorate of Soda.
Year: 1894

page_text: Date of Application, 9th, Oct., 1894
Complete Specification Left, 8th July, 1895, Accepted 10th Aug...1895
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PROVISIONAL, SPECIFICATION.
Improvements in the Manufacture of Chlorate of Soda.
We THOMAS THOMPSON BEST Ph. D. Chemist and JOHN BROCK Director of
The United Alkali Company Limited both of G 11 Exchange Buildings Liverpool
in the County of Lancaster do hereby declare the nature of this invention to be as
'follows:
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This invention has for its object the more economical production of chlorate of
soda. The processes hitherto in use have yielded only a very dilute solution
chlorate of soda while requiring a large quantity of fuel for the concentration
of the solutions. By our improvements we are enabled to produce at once more
concentrated solutions of sodium chlorate, and thus to save a very considerable
amount of the cost of production of this compound.
According to our invention, we pass into a solution of carbonate of soda, as
concentrated as possible, consistent with the temperature, chlorine gas, preferably
diluted with inert gases, until the-solution is fully saturated and smells of chlorine.
We prefer to do this at an ordinary normal temperature and not to allow the
temperature to rise too high. The carbonate of soda is decomposed by the chlorine,
with evolution of carbonic acid-gas, whilst sodium loride and sodium chlorate' are
formed. The carbonic acid escapes together with inert gases which may have
been present in the chlorine gas and carries with it a certain amount of vapour of
hypochlorous acid.
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In order to avoid loss of chlorine or hypochlorous acid during the operation we
employ a series of, vessels for the absorption of the chlorine, the vessels being so
arranged that the gas leaving one of the vessels enters the next and so on, the last
vessel of the series containing an almost fresh solution of carbonate of soda, whilst
the first vessel of the series contains an almost finished solution of chlorate
of soda.
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When the solution in the first vessel of the series is completely saturated with
chlorine, it is emptied and recharged with fresh carbonate of soda solution, and
made the last t vessel in the series by means of suitable connections in the pipes
conveying the chlorine gas.
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insoluble
The finished solutions are then allowed to settle, to free them from any
substances, or they may be filtered when they are ready, for concentration by
evaporation. The sodium chloride,separates during the process of concentrating
and can be removed and the chlorate, may then be obtained by crystallisation on
cooling.
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During the process, of absorbing the chlorine gas, the monocarbonate of soda
passes through the stage of bicarbonate before it is completely converted into the
chloride and chlorate. Where a sufficiently pure bicarbonate of soda is economically
produced we may use a sodium bicarbonate solution in lieu of monocarbonate for
the absorption of the chlorine gas.
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Dated this 9th day of October 1894.
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page_text: Improvements in the Manufacture of Chlorate of Soda.
We, THOMAS THOMPSON BEST Ph. D. Chemist and JOHN BROCK Director of
The United Alkali Company Limited both of G11 Exchange Buildings Liverpool
in the County of Lancaster 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 :-
:
This invention has for its object the more economical production of chlorate of
soda. The processes hitherto in use have yielded only a very dilute solution of
chlorate of soda while requiring a large quantity of fuel for the concentration of
the solutions. By our improvements we are enabled to produce at once more
economical solutions of sodium chlorate, and thus to save a very considerable
amount of the cost of production of this compound.
According to our invention, we pass into a solution of carbonate of soda, as
concentrated as possible consistent with the temperature say of about 1.27 specific
gravity, chlorine gas preferably diluted with inert gases, until the solution is fully
saturated and smells of chlorine. We prefer to do this at the ordinary normal
atmospheric temperature but not exceeding 100 degrees Fahrenheit. The carbonate
of soda is decomposed by the chlorine, with evolution of carbonic acid gas whilst
sodium chloride and sodium chlorate are formed. The evolution of carbonic acid
gas assists in preventing a rapid rise of the temperature, and thus allows of a good
proportion of chlorides and chlorates to be obtained in the resulting liquid. The
carbonic acid escapes together with any inert gases which may have been present
in the chlorine gas and carries with it a certain amount of vapour of hypochlorous
acid.
In order to avoid loss of chlorine or hypochlorous acid during the operation we
employ a series of vessels for the absorption of the chlorine, the vessels being so
arranged that the gas leaving one of the vessels enters the next and so on, the
last vessel of the series containing an almost fresh solution of carbonate of
soda, whilst the 'first vessel of the series contains an almost finished solution of
chlorate of soda.
When the solution in the first vessel of the series is completely saturated with
chlorine, it is emptied and recharged with fresh carbonate of soda solution and
made the last vessel in the series by means of suitable connections in the pipes
conveying the chlorine gas.
The finished solutions are then allowed to settle, to free them from any 'insoluble
substances, or they may be filtered when they are ready for concentration by
evaporation. The sodium chloride separates during the process of concentrating
and can be removed and' the chlorate may then be obtained by crystallisation on
cooling, and may be purified by re-crystallisation.
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During the process of absorbing the chlorine gas, the monocarbonate of soda
passes through the stage of bicarbonate before it is completely converted into
the chloride and chlorate. Where a sufficiently pure bicarbonate of soda is
economically produced we may use a sodium bicarbonate solution in lieu of
monocarbonate for the absorption of the chlorine gas.
In order to more perfectly absorb the chlorine it is better to force it by means
of a pump through the solution and not simply to pass it over the surface of the
liquid. An ordinary pump may be used if the chlorine gas is previously dried
for example as directed in Specification of Letters Patent No. 16131 of 1893.

page_text: 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,
In the manufacture of chlorate of soda the direct production of concentrated'
solutions of chlorate of soda by subjecting solutions of carbonate or bicarbonate
of soda to the action of chlorine at an ordinary normal temperature substantially
as and for the purposes set forth.
Dated this 8th day of July 1895:
JOHNSONS & WILLCOX,
Agents.