AN IMPROVED METHOD OP DRYING CHLORINE GAS
Year: 1871

page_text: LETTERS PATENT to Walter Weldon, of 29, The Cedars, Putney, in
the County of Surrey, for the Invention of "AN IMPROVED METHOD
OP DRYING CHLORINE GAS."
Sealed the 26th March 1872, and dated the 4th November 1871.
PROVISIONAL SPECIFICATION left by the said Walter Weldon at the
Office of the Commissioners of Patents, with his Petition, on the
4th November 1871.
I, WALTER WELDON, of 29, The Cedars, Putney, in the County of
Surrey, do hereby declare the nature of the said Invention for "AN
IMPROVED METHOD OF DRYING CHLORINE GAS," to be as follows:-
In some processes for the manufacture of chlorine, and especially in
those processes which yield the chlorine in a dilute state, the chlorine
obtained is associated with so much moisture that it has to be dried
before it can be applied to the manufacture of bleaching powder. This
drying is effected at present by passing the chlorine or mixture of
chlorine and other gases through towers filled with lumps of chloride of
calcium. The chloride of calcium runs out of these towers in solution

page_text: in the water which it has absorbed from the moist gas or mixture of
gases, and has then to be evaporated down to dryness again.
This evaporation is somewhat costly, and the object of this Invention
is to either cheapen or avoid it, which I accomplish by bringing the gas
or mixture of gases into contact instead of with chloride of calcium
with either chloride of magnesium or quicklimé. The use of chloride
of magnesium cheapens the operation of evaporation by reason of
solution of this chloride giving off its water up to a certain point more
readily than chloride of calcium, but the use of quicklime for absorbing
the moisture from the chlorine or mixture of chlorine and other gases
avoids entirely the necessity of evaporating this moisture, seeing that
the water which it absorbs from the gas or gases simply brings the lime
into the state into which it would otherwise have to be brought by
treatment with water specially for that purpose before it could be
employed for making bleaching powder; I therefore prefer to dry the
chlorine by means of quicklime, and to use the resulting hydrate of
lime for the manufacture of either bleaching powder or chlorates.
When employing chloride of magnesium for the above purpose it is an
advantage to mix the chloride of magnesium with common salt.
SPECIFICATION in pursuance of the conditions of the Letters Patent, 2
filed by the said Walter Weldon in the Great Seal Patent Office on
the 1st May 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WALTER
WELDON, of 29, The Cedars, Putney, in the County of Surrey, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fourth day of November, in the year of our
Lord One thousand eight hundred and seventy-one, in the thirty-fifth
year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Walter Weldon, Her special licence that
I, the said Walter Weldon, my executors, administrators, and assigns,
or such others as I, the said Walter Weldon, my executors, adminis-
trators, and assigns, should at any time agree with, and no others, from
2

page_text: time to time and at all times thereafter during the term therein
expressed, should and lawfully might make, use, excrcise, and vend,
within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "AN IMPROVED METHOD OF
DRYING CHLORINE GAS," upon the condition (amongst others) that I, the
said Walter Weldon, my executors or administrators, by an instrument
in writing under my, or their, or one of their hands and seals, should
particularly describe and ascertain the nature of the said Invention, and
in what manner the same was to be performed, and cause the same to
be filed in the Great Seal Patent Office within six calendar months
next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Walter Weldon, do hereby declare
the nature of my said Invention, and in what manner the same is
to be performed, to be particularly described and ascertained in and
by the following statement :-
In some processes for the manufacturo of chlorine, and especially in
those which yield the chlorine in a dilute state, the chlorine obtained is
associated with so much moisture as to require drying before it can be
applied to the manufacture of bleaching powder. This drying is at
present effected by passing the chlorine or mixture of chlorine and other
gases through towers packed with lumps of chloride of calcium. The
chloride of calcium runs out of these towers in solution in the water
which it has absorbed from the moist gas or mixture of gases, and has
then to be evaporated down to dryness again.
This operation is somewhat costly, and the object of this Invention is
to either cheapen it or avoid it altogether as may be preferred. I
accomplish these objects by bringing the moist gas or mixture of gases
into contact instead of with chloride of calcium as aforesaid either with
chloride of magnesium or with quicklime. The use of chloride of
magnesium lessens the cost of driving off by heat the water absorbed
from the moist gas or mixture of gases, by reason of solution of that
chloride giving off its water up to a certain point, and when proper pre-
caution is used more readily than chloride of calcium does; but the use
of quicklime for absorbing the moisture contained in the chlorine or
mixture of chlorine and other gases entirely avoids this operation of
evaporating off the absorbed moisture, as the water which the lime
absorbs from the moist gas or gases simply brings the limo.into the state

page_text: into which it would have to be brought by treatment with water specially
for that purpose before it could be employed for making bleaching
powder. I therefore prefer to dry the chlorine by means of quicklime.
and to use the resulting hydrate of lime in the manufacture of eithe
bleaching powder or chlorates.
The precaution required when employing chloride of magnesium as
above is to mix it with chloride of sodium, and preferably with not less
than an equivalent thereof. This counteracts its tendency to undergo
decomposition during evaporation of its aqueous solution.
Having thus described the nature of my Invention, and the manner in
which the same is to be performed, I would have it understood that what
I consider to be new and original, and desire to have secured to me by
the herein-before in part recited Letters Patent is as follows:-
Firstly. The drying of chlorine gas, or of a mixture of chlorine and
other gases, by bringing such gas or mixture of gases into contact with
surfaces of chloride of magnesium preferably mixed with chloride of
sodium.
Secondly. The drying of chlorine gas, or of a mixture of chlorine and
other gases, by bringing the said gas or mixture of gases into contact
with surfaces of quicklime, and thereby producing a hydrate of lime
suitable for use in the manufacture of bleaching powder and chlorates,
or otherwise.
In witness whereof, I, the said Walter Weldon, have hereunto set
my hand and seal, this Thirtieth day of April, in the year of
our Lord One thousand eight hundred and seventy-two.
WALTER WELDON. (L.s.)