IMPROVEMENTS IN TREATING MIXED SOLUTIONS OF CHILORATE OF LIME AND CHLORIDE OF CALCIUM
Year: 1881

page_text: LETTERS PATENT to Walter Weldon, of Rede Hall, Burstow, in the County
A coin-
of Surrey, for an Invention of "IMPROVEMENTS IN TREATING MIXED
SOLUTIONS OF CHILORATE OF LIME AND CHLORIDE OF CALCIUM."
munication from abroad by Alfred Rangod Pechiney, of Salindres, in the
Republic of France.
PROVISIONAL SPECIFICATION left by the said Walter Weldon at the
Office of the Commissioners of Patents on the 1st February 1881.
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey.
IMPROVEMENTS IN TREATING MIXED SOLUTIONS OF COLORATE OF LIME AND
CHLORIDE OF CALCIUM." A communication from abroad by Alfred Rangod
Pechincy, of Salindres, in the Republic of France.
The only, chlorates which are at present employed extensively in the industrial
arts are chlorate of potash and chlorate of soda. Chlorate of soda is at present
always manufactured from chlorate of potash, which last is itself obtained by the
reaction of chloride of potassium upon the chlorate of lime of a mixed solution of
chlorate of line and chloride of calcium, produced by treating milk of lime by
an excess of chlorine gas.
The product of the treatinent of milk of lime by chlorine gas is a mixed solution
which should contaiu, according to theory, one equivalent of chlorate of lime and
five equivalents of chloride of calcium. It usually contains, however, more than
this proportion of chloride of calcium. For each equivalent of chlorate of lime in
it, it ordinarily contains from five and a half to six equivalents of chloride of
calcium.
The presence in the product of the treatment of milk of lime by chlorine gas of
these large proportions of chloride of calcium renders this product unsuited for
many applications of which a solution of chlorate of lime containing a smaller
proportion of chloride of calcium would be susceptible.

page_text: Hitherto the said product has been applied only to the manufacture of chlorate
of potash, and in that manufacture the presence with the chlorate of lime of so
much chloride of calcium occasions great inconvenience and considerable loss.
The present Invention consists in certain means of separating chloride of calcium
from the said product, and thereby obtaining solutions of chlorate of lime containing
so little chloride of calcium as to be susceptible of applications for which chlorate
of lime has not hitherto been available, and to be better fitted than the solutions
at present used for the only purpose for which chlorate of lime has hitherto been
employed.
My correspondent, who has communicated to ine the present Invention, has
found that a large part of the chloride of calciumn contained in the product of the
treatment of milk of lime by chlorine gas may be separated therefrom as
oxychloride of calcium by adding to the said product free lime, preferably
hydrated, heating to about 80 centigrade, or about 176° Fahrenheit, and then
allowing to cool. He has found, for example, that a liquor containing 5-6 (live and
six-tenths) equivalents of chloride of calcium per one equivalent of chlorate of
lime, and of a density of 25° Beaumé, corresponding to a specific gravity of about
1205, can have removed from it about 3-6 (three and six-tenths) equivalents of
chloride of calcium by adding to it free lime, preferably hydrated, heating to about
the temperature aforesaid, and then permitting to cool. The quantity of lime
added should be about the quantity corresponding to threo equivalents for each
equivalent of chloride of calcium in the liquor, if a maximum separation of chloride
of calcium is to be obtained. Heating to about 170° Fahrenheit determines the
formation of oxychloride, which on cooling separates out as a crystalline mass
mingled with any excess of lime which may have been used. This crystalline mass
should then be submitted to the action of a hydro-extractor, or other efficient
appliance for separating liquids from solids. There is thus obtained a liquor
containing, for each equivalent of chlorate of lime in it, about two equivalents only
of chloride of calcium."
My correspondent has also found that if a liquor containing from five to six
equivalents of chloride of calcium per one equivalent of chlorate of lime be
evaporated to a certain degree of concentration, it will, on cooling, deposit a
considerable part of its chloride of calcium as hydrated crystals, which, by means
of a hydro-extractor, can be obtained practically free from chlorate, if the con-
centration of the liquor have not been pushed too far, nor the subsequent cooling
carried to too low a point. The evaporation should be stopped when the boiling
liquor has a density of about 48° Beaumé, corresponding to a specific gravity
of about 1.485, and subsequent cooling to about 10° centigrade, or about
50° Fahrenheit, will be sufficient. The quantity of chloride of calcium which
crystallizes out under these conditions is such that the mother-liquor remaining
contains only about 1-2 (one and two-tenths) equivalents of chloride of calcium
for each equivalent of chlorate of lime in it.
My correspondent has further found that by a combination of the two methods
of separating chloride of calcium from the product of the treatment of milk of
lime by chlorine gas which I have just described, he can remove so much chloride
of calcium as to obtain a solution containing, per equivalent of chlorate of lime
in it, only about three-tenths of an equivalent of chloride of calcium. To this
end he first evaporates the crude liquor until its density, while boiling, is about
48° Beaumé, as aforesaid. He then cools to about 50° Fahrenheit, and then
separates the crystals which form. To the mother-liquor he now adds its own
volume of water and three equivalents of lime, preferably hydrated, for each
equivalent of chloride of calcium in it. He then heats to about 176° Fahrenheit
to determine the formation of oxychloride of calcium, and then allows to cool until
the oxychloride of calcium which has thus formed has separated out. He submits
this to efficient filtration by means of a hydro-extractor, or otherwise, and thus
obtains a solution of chlorate of lime containing only about three-tenths of an
equivalent of chloride of calcium.

page_text: It will be understood that my correspondent does not confine himself to the
exact temperatures and densities above set forth, though he believes them to be tho
best. His Invention consists in obtaining solutions of chlorate of lime containing
less chloride of calcium than any solutions of chlorate of lime hitherto obtained
industrially, by separating chloride of calcium from the product of the treatment
of milk of lime by chlorine gas, such separation being effected either by such
treatment of that product by evaporation and cooling as will cause chloride of
calcium to crystallize out from it as such, or by treating that product with lime
and then beating and cooling so as to determine the formation and separation of
oxychloride of calcium, or by a combination of both these methods, substantially
as above described.
The said Invention further includes a subsequent treatment of the oxychloride
of calcium obtained as above indicated. This oxychloride of calcium, even after
filtration by the hydro-extractor or otherwise, may retain an appreciable proportion
of chlorate of lime. It is desirable to utilize this chlorate and also to utilize the
lime of the oxychloride. To this end my correspondent treats the oxychloride of
calcium with hot water in quantity sufficient to decompose it more or less com-
pletely into chloride of calcium and lime. Its lime is now suspended in a solution
containing chiefly chloride of calcium, but containing also some oxychloride of
calcium and some chlorate of lime. This solution is separated from the lime by
filtration or decantation, and is then boiled down until chloride of calcium will
crystallize out from it on cooling. It thereby yields a further quantity of strong
solution of chlorate of lime. The lime which has been separated as above stated
can be used, after suitable washing, for any purpose for which it may be required,
but is specially suitable to be used for the forination of more chlorate by treatment
with chlorine gas, as will be well understood.

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 29th July
1881.
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey.
"IMPROVEMENTS IN TREATING MIXED SOLUTIONS OF CHLORATE OF LIME AND
CHLORIDE OF CALCIUM." A communication by Alfred Rangod Pechiney, of
Salindres, in the Republic of France.
The only chlorates which are at present employed extensively in the industrial
arts are chlorate of potash and chlorate of soda. Chlorate of soda is at present
always manufactured from chlorate of potash, which last is itself obtained by the
reaction of chloride of potassium upon the chlorate of lime of the mixed solution
of chlorate of lime and chloride of calcium, which is produced by treating milk of
lime by an excess of chlorine gas.
The product of the treatment of milk of lime by chlorine gas is a nixed solution,
which should contain according to theory one equivalent of chlorate of line and
five equivalents of chloride of calcium. It usually contains however more than
this proportion of chloride of calcium. For each equivalent of chlorate of lime in it,
it ordinarily contains from five and a half to six equivalents of chloride of calcium.
The presence in the product of the treatment of milk of lime by chlorine gas
of these large proportions of chloride of calcium renders this product unsuited to
many applications of which a solution of chlorate of lime containing a smaller
proportion of chloride of calcium would be susceptible. Hitherto the said product has
been applied only to the manufacture of chlorate of potash, and in that manufacture
the presence with the chlorate of lime of so much chloride of calcium occasions
great inconvenience and considerable loss. The present Invention consists in
certain means of separating chloride of calcium from the said product, and of
thereby obtaining soiutions of chlorate of lime containing so little chloride of
calcium as to be susceptible of applications for which chlorate of lime has not
hitherto been available, and to be better fitted than the solutions at present usel
for the only purpose for which chlorate of lime has hitherto been employed.
My correspondent who has communicated to me the present Invention has found
that a large part of the chloride of calcium contained in the product of the
treatment of milk of lime by chlorine gas may be separated therefrom as
oxychloride of calcium, by adding to the said product free line, heating to a
suitable temperature, and then allowing to cool to ordinary temperatures. He has
found, for example, that a liquor containing 50 (live and six-tenths) equivalents of
chloride of calcium per one equivalent of chlorate of lime, and of a density of
about 25 degrees Beautné, corresponding to a specific gravity of about 1.205, can
have removed from it about 36 (three and six-tenths) equivalents of chloride of
calcium by adding to it free line, and then heating and subsequently cooling as
aforesaid. The quantity of lime to be added, if a maximum separation of chloride
of calcium is to be effected by this method, should be the quantity equal to about
three equivalents for each equivalent of chloride of calcium in the liquor. It is
convenient to add the lime in the state of hydrate; if it be added in the anhydrous
state, water equal to the quantity required for its hydration must be added also.
The liquor to which lie has thus been added must be heated to at least 176 degrees
Fahrenheit, but it is better to heat it to ebullition. On cooling to ordinary
temperatures oxychloride of calcium will then crystallize out. The resulting
mixture of oxychloride of calcium, with any excess of lime which may have been
employed, and with mother-liquor must then be submitted to efficient filtration, by
means either of the centrifugal hydro-extractor or of any other suitable appliance for

page_text: separating liquids from solids. The filtrate will be a liquor containing for each
equivalent of chlorate of lime in it about two equivalents only of chloride of
calcium.
My correspondent has also found that if a liquor containing from five to six
equivalents of chloride of calcium per one equivalent of chlorate of lime be
evaporated to a certain degree of concentration, and be then cooled to a certain
point, it will deposit a considerable part of its chloride of calcium as hydrated
crystals, which by means of a hydro-extractor or other suitable appliance for
separating solids from liquids can be freed from mother-liquor so far as to retain
only a very small proportion of chlorate. The evaporation should be carried until
the boiling liquor has a density of about forty-eight degrees Beauné, corresponding
to a specific gravity of about 1-485. The subsequent cooling should be carried to
fifty degrees Fahrenheit or a little lower, but should not be carried below forty-seven
degrees Fahrenheit. At above fifty degrees Fahrenheit a maximumn separation of
chloride of calcium would not be obtained, while at about forty-seven degrees
Fahrenheit chlorate of lime would begin to separate out also. When the liquor before
cooling has a specific gravity of about 1485, and it is cooled to fifty degrees Fahrenheit
or a little below, the quantity of chloride of calcium which crystallizes out is such
that when these crystals have been separated from their mother-liquor by suitable
means of filtration or otherwise their inother-liquor will contain, per equivalent of
chlorate of lime in it, only about 1-2 (or one and two-tenths) equivalents of chloride
of calcium.
My correspondent has further found that by a combination of the two methods
of separating chloride of calcium from the product of the treatment of milk of lime
by chlorine gas, which I have just described, he can remove so much chloride of
calcium as to obtain a solution containing, per equivalent of chlorate of lime in it,
only about three-tenths of an equivalent of chloride of calcium. To this end he
first evaporates the crude liquor until its density while boiling is about 1-485, as
aforesaid. He then cools to or a little below fifty degrees Fahrenheit. He then
filters to separate the chloride of calcium which has crystallized out, and then to
the mother-liquor he adds either its own volume of water and three equivalents of
hydrate of lime per equivalent of chloride of calcium in it, or a little more than its
own volume of water and, per equivalent of chloride of calcium in it, three equi-
valents of anhydrous lime. He then heats the mixture to not less than 176 degrees
Fahrenheit, but preferably to ebullition, and thereby determines the formation of
oxychloride of calcium. He then allows the product to cool to ordinary
temperatures, and when it has done this he submits it to efficient filtration by
means of either a centrifugal hydro-extractor or any other suitable appliance.
The filtrate is a solution of chlorate of lime containing only about three-tenths of
an equivalent of chloride of calcium for each equivalent of chlorate of lime in it.
It will be understood that my correspondent does not confine himself to the exact
temperatures and densities above set forth, though he believes them to be best. His
Invention consists in obtaining solutions of chlorate of lime containing less chloride
of calcium than any solutions of chlorate of lime hitherto obtained industrially by
separating chloride of calcium from the product of the treatment of milk of lime
by chlorine gas, such separation being effected either by such treatment of that
product by evaporation and cooling as will cause chloride of calcium to crystallize
out from it as such, or by treating that product with lime, and then heating and
afterwards cooling so as to determine the formation and separation of oxychloride
of calcium, or by a combination of both these methods, substantially as above
described.
The said Invention further includes a subsequent treatment of the oxychloride
of calcium obtained, as above indicated. This oxychloride of calcium, after filtration
by the hydro-extractor or otherwise, retains an appreciable proportion of chlorate
of lime. It is desirable to utilize this chlorate, and also to utilize the lime of the
oxychloride. To this end my correspondent treats the oxychloride of calcium with
hot water in quantity sufficient to decompose it into chloride of calcium and lime.

page_text: This
Its lime is now suspended in a solution containing chiefly chloride of calcium, but
containing also soine oxychloride of calcium and some chlorate of lime.
solution is separated from the lime by filtration or decantation, and is then boiled
down until chloride of calcium will crystallize out from it on cooling. It thereby
yields a further quantity of strong solution of chlorate of lime. The lime which
has been separated, as above stated, can be used after suitable washing for any
purpose for which it may be required, but is specially suitable to be used, without
washing, for the formation of more chlorate by treatment with chlorine gas, as
will be well understood.
In witness whereof, I, the said Walter Weldon, have hereunto set my hand
day of July, in the year of our Lord One thousand
.
and scal, this
eight hundred and eighty-one.
WALTER WELDON. (L.S.)