IMPROVEMENTS IN THE PURIFICATION OF ALKALINE SOLUTIONS
Year: 1881

page_text: LETTERS PATENT to Eustace Carey, Holbrook Gaskell, the younger, and
Ferdinand Hurter, Ph.D., all of Widnes, in the County of Lancaster, Alkali
Manufacturers, for an Invention of "IMPROVEMENTS IN THE PURIFICATION OF
ALKALINE SOLUTIONS."
PROVISIONAL SPECIFICATION left by the said Eustace Carey, Holbrook
Gaskell, the younger, and Ferdinand Hurter at the Office of the Commissioners
of Patents on the 17th March 1881.
EUSTACE CAREY, HOLBROOK GASKELL, the younger, and FERDINAND
HURTER, Ph.D., all of Widnes, in the County of Lancaster, Alkali Manu-
facturers. "IMPROVEMENTS IN THE PURIFICATION OF ALKALINE SOLUTIONS."
Solutions of soda or potash frequently contain silica and alumina.
When desired these impurities are usually removed or partially removed by
passing carbonic acid through the solutions, thereby precipitating silica and
alumina.
Silica and alumina so precipitated separate in combination; but if the silica is
in excess of the quantity necessary for combination with the alumina present, such
excess is not precipitated.
Our Invention relates to solutions containing an excess of silica, and in order to
remove such excess we add to the solution before, during, or after carbonating,
oxide or hydrate or salt of aluminium in quantity sufficient at the least with the
alumina already contained to cause the precipitation of the whole of the silica, and
we prefer to add an excess of alumina as any such excess can be removed by
carbonic acid.
This process may advantageously be used in combination with the process for
which Letters Patent were granted to us and dated July 18th, 1879, No. 2939, and
000

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Eustace Carey, Holbrook Gaskell, the younger, and Ferdinand Hurter
in the Great Seal Patent Office on the 12th September 1881.
EUSTACE CAREY, HOLBROOK GASKELL, the younger, and FERDINAND
HURTER, Ph.D., all of Widnes, in the County of Lancaster, Alkali Manu-
facturers. "IMPROVEMENTS IN THE PURIFICATION OF ALKALINE SOLUTIONS."
Solutions of soda or potash frequently contain silica and alumina.
When desired these impurities are usually removed or partially removed by
passing carbonic acid through the solutions, thereby precipitating silica and alumina.
silica and alumina so precipitated separate in combination; but if the silica is in
excess of the quantity necessary for combination with the alumina present, such
excess is not precipitated.
Now our said Invention relates to solutions containing an excess of silica, and in
order to remove such excess we add to the solution before or during the carbonating
process, oxide or bydrate or salt of aluminium in quantity sufficient at the least
with the alumina already contained to cause the precipitation of the whole of the
silica, and we prefer to add an excess of alumina, as any such excess can be removed
by carbonic acid.
In carrying out our said Invention we prefer to operate in the following
manner: We find it convenient to add the alumina in solution. Such a solution
can be readily obtained by the use of the mineral known as "bauxite."
When dealing with soda solutions we prepare a solution of alumina in caustic
soda by treating pulverized bauxite with a hot or boiling solution of caustic soda
of about 1.15 specific gravity, until the soda is saturated or nearly saturated with
alumina.
When dealing with potash solutions we prepare a solution of alumina in caustic
potash in a similar manner.
We then add to and ultimately mix with the alkaline solution to be purified
such a quantity of this solution of alumina as to insure the complete precipitation
of the silica. We ascertain when enough alumina has been added by placing a
small sample of the solution in a test tube, adding an excess of a saturated solution
of bicarbonate of soda, boiling and filtering; if the addition of chloride of ammo-
nium to the filtrate and boiling produces a precipitate, enough alumina has not been
added. We continue to add alumina to the alkaline solution until a sample treated
with chloride of ammonium as above shows no precipitate.
When sufficient alumina has been added we pass carbonic acid gas, or a mixture
of carbonic acid gas and air, through the solution, preferably keeping the solution
boiling, or at a temperature approaching the boiling point, until the whole of
the silica and alumina are precipitated, the silica and alumina so precipitated
can be readily separated from the solution by settling or filtration in the usual
manner.
This process may advantageously be used in combination with the processes for
which certain former Letters Patent were granted to us dated July 18th, 1879,
No. 2939, and February 11th, 1880, No. 608. When applying our present process
together with those processes for decomposing ferrocyanides, we prepare the alkaline
solutions as herein before described, that is to say, we first add the necessary
quantity of alumina in order to ensure complete precipitation of all the silica in
the subsequent operation. We then proceed exactly as described in our said former
Specifications.
The addition of the alumina has also the effect of diminishing incrustation in
the high pressure boiler described in the Specification to our said former Letters
Patent No. 2939, in the year of our Lord 1879.

page_text: Having now described and particularly. ascertained the nature of our said
Invention, and the manner in which the same is or may be used or carried into
effect, we would observe in conclusion that what we consider to be novel and
original, and therefore claim as the Invention secured to us by the hereinbefore in
part recited Letters Patent is,-
In the purification of alkaline solutions the addition of alumina to the solution,
substantially in the manner and for the purpose hereinbefore described.
In witness whereof, we, the said Eustace Carey, Holbrook Gaskell, the
younger, and Ferdinand Hurter, have to this our Specification set our hands
and seals, the 10th day of September, One thousand eight hundred and
eighty one.