IMPROVEMENTS IN THE PRODUCTION OF CHLORINE AND HYDROCHLORIC ACID FROM SOLUTIONS OF CHLORIDE OF CALCIUM
Year: 1885

page_text: I, THOMAS TWYNAM of 137 Fellows Road South Hampstead London Analytical
Chemist do hereby declare the nature of my invention for IMPROVEMENTS IN THE
PRODUCTION OF CHLORINE AND HYDROCHLORIC ACID FROM SOLUTIONS OF CHLORIDE
OF CALCIUM to be as follows:-
•
This invention relates to improvements in the production of chlorine and hydro-
chloric acid from solutions of chloride. of calcium which are obtained as waste
products in many manufacturing operations, more especially in the manufacture of
soda by the ammonia process and in the Weldon process for the recovery of
manganese.
To the solution of chloride of calcium, previously freed from any iron by a
preliminary precipitation with lime or chalk, sufficient lime is added to form with
the dissolved chloride of calcium oxychloride of calcium, that is there should be
added for every equivalent of chloride of calcium present at least three equivalents
of lime. The mixture is then heated nearly or quite to boiling, the lime being kept
well agitated, until the formation of oxychloride is determined. When the solution
of chloride of calcium is very dilute it will have to be somewhat concentrated in
.order to cause the oxychloride to form The heating with lime may be advan-
tageously performed under pressure.
The solution is allowed to cool to the ordinary temperature of the air and the
oxychloride of calcium, which crystallizes out, separated from the mother liquor.
The crystals thus obtained are heated in a current of air, or of air and steam if it
be required to produce chiefly hydrochloric acid, the heat being cautiously raised.
If a large quantity be heated at a time the steain may be wholly or partly omitted,
or the crystals may be heated in two separate chambers in the first of which the
heat should be just sufficient to drive off from the crystals the water of crystalliza-
tion they contain, the steam thereby formed being caused to pass into a second
chamber in which previously dehydrated crystals are more strongly heated. If it
be desired to obtain chiefly chlorine in the free state the crystals should be first
deprived of their water of crystallization and then strongly heated in a current of
dry air. The presence of silica facilitates the decomposition of the oxychloride
crystals.

page_text: Improvements in the Production of Chlorine and Hуarocnioric
Acid from Solutions of Chloride of Calcium.
I THOMAS TWYNAM, of 137, Fellows Road, South Hampstead London, do hereby
declare the nature of this invention and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:
This invention relates to improvements in the production of chlorine and hydro-
chloric acid from chloride of calcium solutions, which are at present obtained as
waste products in many manufacturing operations more especially in the manu-
facture of carbonate of soda by the ammonia process and in the Weldon process for
the recovery of manganese.
To the solution of chloride of calcium previously freed from any dissolved iron by
a preliminary precipitation with lime or chalk, a sufficient quantity of pure lime is
added to form with the dissolved chloride of calcium oxychloride of calcium that
is for every equivalent of chloride of calcium present in the solution rather more
than three equivalents of lime must be added, the lime used must be free from
carbonate and is preferably added in the form of milk of lime.
To cause the formation of the oxychloride of calcium the solution must be beated
to at least 80° C and the lime kept constantly agitated in the solution. The heating
of the solution may be conveniently effected by means of a steam jet, which may be
made to keep the lime well agitated The time required for the formation of the
oxychloride varies with the strength of the chloride of calcium solution; with very
weak solutions part of the water has first to be evaporated. When the heating has
been sufficiently long continued the undissolved lime is allowed to settle together
with any sodic chloride which may have crystallized out, the solution being kept
still hot. The clear liquor is run off from this and allowed to cool to the tempera-
ture of the air, when the oxychloride crystals will freely form, they are to be
separated from the mother liquor which consists of a weak solution of chloride of
calcium which is preferably run to waste.
The water of crystallization is first driven off from the crystals by gently heating
them by waste heat, the steam produced may be collected and utilized; practically
no hydrochloric acid vapour is driven off with the steam.
The resulting dry powder consists of an intimate mixture of chloride of calcium
and lime. On strongly heating it in a current of air the chloride of calcium is
largely decomposed, hydrochloric acid and free chlorine gases being given off which
may be collected and utilized by well known methods. I prefer the heating should
be so effected that the products of combustion are not mixed with evolved gases.
The lime present in the dried mixture prevents the fusion of the chloride of
calcium.
Although air alone aided by heat is able to largely decompose the chloride,
air and steam acts somewhat more completely but in this case the result is the
production of hydrochloric acid only; the presence of silica also facilitates the
decomposition.

page_text: When steam (preferably superheated) and air are employed together prefer to
have two separate chambers in one of which the hydrated oxychloride crystals
are heated the steam thereby formed being caused to pass into a second chamber in
which previously dehydrated crystals are strongly heated. The lime remaining
after the decomposition of the chloride may be again used in the formation of fresh
oxychloride of calcium.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
The process for recovering chlorine from solutions of chloride of calcium either
as hydrochloric acid or a mixture of hydrochloric acid and free chlorine by forming
and crystallizing oxychloride of calcium and subsequently decomposing it by
strongly heating the dehydrated crystals in presence of air or of air and steam
substanstially as described.