IMPROVEMENTS IN THE MANUFACTURE OF SULPHATE OF ALUMINA
Year: 1878

page_text: LETTERS PATENT to Edwin Powley Alexander, of 14, Southampton Buildings,
in the County of Middlesex, Consulting Engineer and Patent Agent, for the
Invention of "IMPROVEMENTS IN THE MANUFACTURE OF SULPHATE OF
ALUMINA." A. communication from abroad by Francis Laur, of Paris, in the
Republic of France. Engineer.
Sealed the 23rd August 1878, and dated the 25th February 1878.
PROVISIONAL SPECIFICATION left by the said Edwin Powley Alexander
at the Office of the Commissioners of Patents on the 25th February 1878.
EDWIN POWLEY ALEXANDER, of 14, Southampton Buildings, in the County of
Middlesex, Consulting Engineer and Patent Agent. IMPROVEMENTS IN THE MANU-
FACTURE OF SULPHATE OF ALUMINA." A communication from abroad by Francis
Laur, of Paris, in the Republic of France, Engineer.
"
This Invention relates to a peculiar process for the manufacture or production
from aluminous earths containing more or less iron, such, for example, as clay,
kaolin, and the like, and by preference from the hydrates of alumina, known as
bauxite, containing from 50 to 80 per cent. of alumina, of a sulphate of alumina
completely neutral and free, or nearly so, from iron, a result which has never
hitherto been attained commercially.
In carrying out this Invention I pour, say, about 440 pounds avoirdupois of
sulphuric acid of 50° Beaumé into a leaden vat, and raise the temperature thereof
by a jet of free steam. When the acid commences to boil I add thereto from about
242 to 286 pounds avoirdupois of bauxite (bydrate of alumina) in the form of
powder. After a few minutes a powerful re-action commences, and the mixture
(which before the re-action should not occupy more than 1/6th the capacity of the
vat) will overflow even, unless care be taken to add thereto at this moment about

page_text: 13 to 14 gallons (more or less) of water. The mixture is then allowed to remain in
the vat, and should it recommence to overflow more water is to be added. After
the expiration of about one hour the mixture will have returned to its original
volume. Water may then be added at will, according to the degree of concentration
required, thus obtaining a solution of sulphate of alumina containing about one-
half per cent. of iron in combination. The silica of the bauxite and the bauxite not
attacked deposit slowly, and may be readily separated by decantation.
In order to obtain sulphate of alumina free from iron it is simply necessary to
introduce plates of old zinc into the ferrugenous solution (say, from 61%, to 11 lbs.
in the example given). The zinc is attached, and after 4 or 5 hours (under heat),
or one or two days (under cold), the iron is precipitated in the form of a black
powder, which deposits at the same time as the silica. The deposition having been
accomplished the limpid solution, which is absolutely neutral, and does not turn
blue in presence of prussiate of potash, is decanted or syphoned off.
With the quantities given above about 660 pounds avoirdupois of sulphate of
alumina in solution is obtained, which is concentrated to 45° Beaumé (under heat),
and poured into casks in the ordinary manner.
.It is essential to employ a bauxite reduced or ground to a very fine state of
division, or to increase the proportion in order to obtain at once a neutral or nearly
neutral solution, the ellimination of the iron being based on the fact that whilst in
an acid solution of ferrugenous sulphate of alumina the metallic zinc allows only
the iron (Fe 0³) to pass to the minimum of oxidation (Fe O), in a neutral solution
it precipitates entirely the peroxide of iron and replaces it.
The product obtained by the said improved process is a sulphate of alumina
possessing the following special characteristics, namely:-It is completely exempt
from the presence of free acid; is not hygrometric, and consequently does not
absorb moisture; and is moreover capable of being ground to any degree of
fineness.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Edwin Powley Alexander in the Great Seal Patent Office on the
23rd August 1878.
EDWIN POWLEY ALEXANDER, of 14, Southampton Buildings, in the County of
Middlesex, Consulting Engineer and Patent Agent. "IMPROVEMENTS IN THE MANU-
FACTURE OF SULPHATE OF ALUMINA." A communication from abroad by Francis
Laur, of Paris, in the Republic of France, Engineer.
The said Invention relates to a peculiar process for the manufacture or produc-
tion from aluminous earths containing more or less iron (such, for example, as clay,
kaolin, and the like, and by preference from the hydrates of alumina known as
bauxite, containing from 50 to 80 per cent. of alumina), of a neutral sulphate of
alumina, free, or nearly so, from iron, a result which has never hitherto been
attained commercially.
In carrying out the said Invention pour, say, about 440 pounds avoirdupois of
sulphuric acid, of 50° Beaumé, into a leaden vat or lead-lined tank, and raise the
temperature thereof by a jet of free steam. When the sulphuric acid commences to
boil I add thereto from about 242 to 286 pounds avoirdupois of bauxite (hydrate of
alumina) in the form of powder. After a few minutes a powerful re-action takes
place, the mixture (which before the re-action should not occupy more than about
/th the capacity of the vat) overflowing the sides of the vessel unless care be taken
to add thereto at this moment about 13 to 14 gallons (more or less) of water. The
mixture is then allowed to remain in the vat, and should it recommence to overflow
more water is to be added. After the expiration of about one hour the mixture
will have returned to its original volume. More water may then be added at will,
according to the degree of concentration required, thus obtaining a solution of
sulphate of alumina containing about one-half per cent. of iron in combination.
The silica of the bauxite and the bauxite not attacked deposit slowly, and may be
readily separated by decantation.
In order to obtain sulphate of alumina free from iron it is simply necessary to
introduce plates of old zinc into the solution of ferrugenous sulphate (say from
about 6%, to 11 lbs. in the example given). The zinc is attacked, and after 4 or 5
hours (under heat) or one or two days (under cold) the iron will be precipitated in
the form of a black powder, which deposits at the same time as the silica. After
this deposition has been accomplished the limpid solution, which is absolutely
neutral, and does not turn bluish in presence of prussiate of potash, is to be decanted
or syphoned off.
With the quantities given above about 660 pounds avoirdupois of sulphate of
alumina in solution is obtained, which is to be concentrated to about 45° Beaumé
(under heat), and poured into casks in the ordinary manner.
It is essential to employ a bauxite reduced or ground to a very fine state of
division, or to raise the proportion in order to obtain at once a neutral or nearly
neutral solution, the elimination of the iron being based on the fact that whilst in
an acid solution of ferrugenous sulphate of alumina the metallic zinc allows only the
iron (Fe 0) to pass to the minimum of oxidation (Fe O), in a neutral solution it
precipitates entirely the peroxide of iron and replaces it.
The new product obtained by the herein-before described improved process is a
sulphate of alumina possessing the following special characteristics, namely:-1, it
is completely exempt from the presence of free acid; 2, it is not hygrometric, and
consequently does not absorb moisture; 3, it is capable of being ground to any
degree of fineness; 4, the per-centage of basic matter that is formed in the sulphate
of alumina may extend to 20 per cent., but is never less than 18 per cent.
Having now described and particularly ascertained the nature of the said
Invention, and the manner in which the same is or may be used or carried into

page_text: effect, I would observe in conclusion that what I consider to be novel and original,
and therefore claim as the Invention secured to me by the herein-before in part
recited Letters Patent is, the peculiar process for the manufacture of sulphate of.
alumina, as herein-before described.
:
In witness whereof, I, the said Edwin Powley Alexander, have hereunto set
my hand and seal, this Twenty-third day of August, in the year of our
Lord One thousand eight hundred and seventy-eight.
EDWIN P. ALEXANDER. (LS.)