IMPROVEMENTS IN THE MANUFACTURE OF SODA AND POTASH
Year: 1878

page_text: LETTERS PATENT. to James Mactear, of Glasgow, in the County of Lanark,
North Britain, Chemist, for the Invention of "IMPROVEMENTS IN THE
MANUFACTURE OF SODA AND POTASH."
Sealed the 10th December 1878, and dated the 3rd August 1878.
PROVISIONAL SPECIFICATION left by the said James Mactear at the Office
of the Commissioners of Patents on the 3rd August 1878.
JAMES MACTEAR, of Glasgow, in the County of Lanark, North Britain, Chemist.
"IMPROVEMENTS IN THE MANUFACTURE OF SODA AND POTASH."
This Invention relates to the improved mode of furnacing sulphate of soda or of
potash described in the Specification of Letters Patent granted to the present
applicant, and dated 22 September 1874 (No. 3242), and comprises improvements
which are also applicable in the ordinary process of furnacing employed in the
manufacture of soda and potash, although probably not with as much advantage as
when combined with the improved process referred to.
In the said improved process a small quantity of caustic lime is added to the
mixture of sulphate, coal, and carbonate of lime at or near the end of the re-action;
and the present Invention consists in adding before or along with such caustic lime
a small quantity of one or other, or a mixture of any of the substances herein-after
specified. These substances are such as will yield oxygen when mixed with the
charge, and will thereby cause the evolution or removal of the cyanogen compounds
ordinarily present in black ash, and thus save the trouble and expence hitherto
incurred in subsequently removing such cyanogen compounds.
It is important that the oxygen yielding substances should be such as not them-
selves to involve extra cost or difficulties in the subsequent processes; and therefore
amongst such as might otherwise be suitable the following are selected, namely,

page_text: sulphate of lime, sulphate of baryta, sulphate of strontia, sulphate of manganese, and
oxides of iron or magnesia. Of these substances the cheapest is to be preferred,
namely, the sulphate of lime or gypsum, which may be either natural or in the
form of plaster of Paris, and by preference containing water, which water may aid
or contribute to the intended decomposing action.
The precise proportion of the oxygen yielding substance to be used will vary
with its nature and with the proportion of cyanogen compounds likely to be present
in the furnace charge; but as an example it may be stated that when sulphate of
lime is used about five parts by weight of it should be added for every hundred
parts of sulphate originally in the charge.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent_filed by
the said James Mactear in the Great Seal Patent Office on the 1st February
1879.
JAMES MACTEAB, of Glasgow, in the County of Lanark, North Britain, Chemist.
"IMPROVEMENTS IN THE MANUFACTURE OF SODA AND POTASH."
My said Invention relates to the improved mode of furnacing sulphate of soda or
of potash, described in the Specification of Letters Patent granted to me, and dated
22 September 1874 (No. 3242), and comprises improvements which are also
applicable in the ordinary process of furnacing employed in the manufactures of
soda and potash, although probably not with as much advantage as when combined
with the improved process referred to.
In the said improved process a small quantity of caustic lime is added to the
mixture of sulphate, coal, and carbonate of lime at or near the end of the re-action;
and my present Invention consists in adding before or along with such caustic lime,
or when about to draw the charge from the furnace, a small quantity of one or
other, or a mixture of any of the substances herein-after specified. These substances
are such as will yield oxygen when mixed with the charge, and will thereby cause
evolution or removal of the cyanogen compounds ordinarily present in black ash,
and thus save the trouble and expense hitherto incurred in subsequently removing
such cyanogen compounds.
It is important that the oxygen yielding substances should be such as not them-
selves to involve extra cost or difficulties in the subsequent processes, and therefor
amongst such as might otherwise be suitable, the following are selected, namely
sulphate of lime, sulphate of baryta, sulphate of strontia, sulphate of magnesia, and
oxides of iron or manganese. Of these substances the cheapest is to be preferred,
namely, sulphate of lime or gypsum, which may be either natural or in the form of
plaster of Paris, and by preference containing water, which water may aid or con-
tribute to the intended decomposing action.
The precise proportion of the oxygen yielding substance to be used in practically
carrying out my said Invention will vary with its nature and with the proportion
of cyanogen compounds likely to be present in the furnace charge; but as an
example I may state that when sulphate of lime is used about five parts by weight
of it should be added for every hundred parts of sulphate of soda or potash
originally in the charge.
As another example I may state that when peroxide of iron is used I have found
that even less than one part by weight of every hundred parts of sulphate of soda
or of potash is sufficient to decompose the cyanogen compounds in ordinary cases.
In some cases I find that the soda liquor obtained when adopting my improved
process, herein-before described, may be advantageously treated with carbonic acid, a
remarkably pure alkali being thereby at once obtained.
Having thus particularly described my said Invention, and the manner of per-
forming the same, I have to state that I do not restrict myself to the precise details
herein-before specified, but that what I believe to be novel and original, and claim
as the Invention secured to me by and in terms of the herein-before in part recited
Letters Patent is, the system of furnacing sulphate of soda or of potash wherein one
or other or a mixture of any of the oxygen yielding substances herein-before
specified is mixed with the charge at or near the end of the re-action, substantially
as and for the purposes herein-before described.
In witness whereof, I, the said James Mactear, have hereunto set my hand
and seal, this Thirty-first day of January, in the year of our Lord One
thousand eight hundred and seventy-nine.