IMPROVEMENTS IN OBTAINING AND TREATING COMPOUNDS OF ALUMINA
Year: 1862

page_text: LETTERS PATENT to Alfred Noble, of Bristol, in the County of Gloucester,
Analytical Chemist, for the Invention of "IMPROVEMENTS IN OBTAINING
AND TREATING COMPOUNDS OF ALUMINA."
Sealed the 21st January 1863, and dated the 28th July 1862.
PROVISIONAL SPECIFICATION left by the said. Alfred Noble at the
Office of the Commissioners of Patents, with his Petition, on the 28th
July 1862.
I, ALFRED NOBLE, of Bristol, in the County of Gloucester, Analytical
Chemist, do hereby declare the nature of the Invention for "IMPROVEMENTS
IN OBTAINING AND TREATING COMPOUNDS OF ALUMINA, to be as follows:-
This Invention has for its object improvements in obtaining and treating
compounds of alumina. In order to obtain a preparation of alumina, which
for many purposes may be used as a substitute for alum, I take clay or material
containing variable quantities of alumina, oxide of iron, and water, and treat
it with hydrochloric acid, in the following manner: After having ground the
clay to a fine powder and calcined it in a reverberatory or other furnace, I
expose it to the action of hydrochloric acid gas (as it comes from the furnaces
in the ordinary plan of making salt cake, or obtained in any other way), care
being taken that the temperature of the gas is somewhere about 200° Fahren-
heit. If the temperature is too high, no action takes place, and if too
low the compound becomes partly liquified, which is inconvenient. When
the operation has been successfully performed, the resulting substance, which
ΓΡ

page_text: I call crude chlor-alum cake, is in a dry state, and consists of a mixture
of chloride of aluminium, with chloride of iron, silica, water, and other
substances
My Invention also relates to the purification of the crude chlor-alum cake
from iron and free acid. This I effect as follows:-The crude cake is kept
moderately heated for some time, and a current of air may be passed over it,
but this is not essential. By this means all free hydrochloric acid is driven
off, and the greater part of the chloride of iron in the cake becomes decom-
posed, hydrochloric acid being driven off and oxide of iron remaining. When
the chlor-alum cake is now treated with water, the chloride of aluminium dis-
solves, but the oxide of iron remains insoluble, and together with the silica is
easily separated by filtration or subsidence. By this means an almost pure
solution of chloride of aluminium is obtained. It is suitable for the purposes
of the dyer and paper-maker.
A pure entirely soluble solid chloride of aluminium may be obtained by
evaporating the solution obtained as above described, and I should prefer
sending the material into the market in the state of the purified cake; but for
many purposes the separation of the iron would be of no importance, and in
that case the crude cake might be used. The solution of chloride of
aluminium may be evaporated to dryness and calcined, by which a very pure
form of alumina is obtained, suitable for the manufacture of aluminium,
aluminate of soda, acetate of alumina, or any aluminous compound.
If this operation is carried on in suitable vessels, and the evolved fumes
condensed, a very pure and concentrated form of hydrochloric acid is obtained.
The same result can be obtained by calcining the chlor-alum cake, but in this
case the residue will contain silica and oxide of iron in addition to the alumina.
The process above described for purifying the crude chlor-alum cake, is
applicable to the purification of impure chloride of aluminium, in whatever
manner the same may be obtained, when it is required to separate therefrom
iron or free acid.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Alfred Noble in the Great Seal Patent Office on the
28th January 1863.
TO ALL TO WHOM THESE PRESENTS SHALL COME, 1, ALFRED
NOBLE, of Bristol, in the County of Gloucester, Analytical Chemist, send
greeting

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-eighth day of July, in the year of our Lord
One thousand eight hundred and sixty-two, in the twenty-sixth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said Alfred Noble, Her special licence that I, the said Alfred Noble, my
executors, administrators, and assigns, or such others as I, the said Alfred
Noble, my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter during the
term therein expressed, should and lawfully might make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "INPROVEMENTS IN OBTAINING
AND TREATING COMPOUNDS OF ALUMINA," upon the condition (amongst others)
that I, the said Alfred Noble, my executors or administrators, by an instru-
ment 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 Alfred Noble, do hereby declare the
nature of the said Invention, and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement
thereof, that is to say:-.
This Invention has for its object improvements in obtaining and treating
compounds of alumina.
In order to obtain a preparation of alumina which for many purposes may be
used as a substitute for alum, I take clay or material containing variable
quantities of alumina, oxide of iron, and water, and treat it with hydrochloric
acid in the following manner:-I take the clay or other material and after
having ground it to a fine powder and calcined it in a reverberatory furnace at
a low red heat, I expose it to the action of hydrochloric acid gas, (which is
taken as it comes from the furnaces in the ordinary plan of making salt cake,
or it may be obtained in any other convenient way,) care being taken that the
temperature of the gas is somewhere about 200° Fahrenheit. If the tempera-
ture is too high no action will take place, and if too low the compound will
become partly liquified. When the operation has been successfully performed
the resulting substance, which I call crude chlor-alum is in a dry state; it
consists of a mixture of chloride of aluminium with some chloride of iron,
silica, water, and other substances. The apparatus I find suitable for carrying
on this operation consists of a chamber built of sandstone, fire-brick, or other

page_text: material little acted on by hydrochloric acid and furnished with shelves of the
same material arranged in such a manner that the current of hydrochloric
acid gas shall circulate over each. The prepared clay is thinly spread (say in
layers from one to two inches in thickness) on these shelves. A good plan is
to place the chamber in such a position that the hydrochloric acid gas can
pass through the chamber on its passage from salt cake furnaces to the usual
condensing towers, so that all the hydrochloric acid gas not absorbed by the
clay passes on to the tower and is condensed in the usual way. Where several
salt cake furnaces are in connection with one flue or passage the temperature
of the gases therein may with ordinary care in working the furnaces be kept
tolerably uniform, and it is then only necessary to take the gases from a part
of the flue or passage in which the temperature is found practically to be
about what is required. Or the acid gases from the salt cake pots may be
led away by passages separately, other flues receiving the heated gas and air
from the roasters, and then the temperature of the gases may be raised, should
they be found to be too low, by admitting to the chamber together with the
gases from the pot some of the hot air and gas from the roaster. When the
clay or other material appears thoroughly acted on, that is to say, when it
appears to have thoroughly penetrated the layers of clay, which I find to be
the case in about 24 hours, the resulting product is drawn out by means of
rakes, and it may in this form, as crude chlor-alum, be sent into the market,
but this I do not usually prefer, I consider it better to submit it to the second
operation of my Invention, which relates to the purification of the crude chlor-
alum (formed as herein-before described), from iron and free acid; this I effect
as follows: The crude chlor-alum is kept heated for some time, and the
temperature I find best for this purpose is between 212° and 240° Fahrenheit,
and it is well to pass a current of air over it, by which means I find that all
free hydrochloric acid is driven off, and that the greater part of the chloride of
iron in it becomes decomposed; hydrochloric acid being driven off and oxide
of iron remaining. The way in which I prefer to carry on this operation is
to spread the crude chlor-alum on an ordinary drier consisting of a tile or
brick floor or surface with flues passing under them, and furnished with
dampers so as to keep the temperature between the above-named limits
videlicit 2120-240° Fahrenheit. The material is to be kept constantly stirred
and turned over, lumps being broken down until hydrochloric acid gas ceases
to be evolved in any quantity. When chlor-alum thus prepared is treated
with water, chloride of aluminium dissolves, but the oxide of iron remains
insoluble and together with the silica is easily separated by filtration or
subsidence. By this means an almost pure solution of chloride of aluminium

page_text: is obtained, and is suitable for the use of the dyer, paper maker, and for other
purposes for which alum is now commonly employed. The process above
described for purifying the crude chlor-alum is applicable to the purification of
impure hydrated chloride of aluminium in whatever manner the same may be
obtained when it is required to separate therefrom iron or free acid. A pure
entirely soluble chloride of aluminium may be obtained by evaporating the solu-
tion obtained as before described. The solution of chloride of aluminium may
be evaporated to dryness and calcined, by which a very pure form of alumina is
obtained suitable for the manufacture of aluminium, of aluminate of soda, of
acetate of alumina, or other aluminous compounds. If this operation is carried
on in suitable vessels and the evolved fumes condensed. a very pure concen-
trated form of hydrochloric acid is obtained. The same result can be obtained
by calcining the crude chlor-alum, but in this case the residue will contain
silica and oxide of iron in addition to the alumina.
In witness whereof, I, the said Alfred Noble, have hereunto set my
hand and seal, this Thirtieth day of December, in the year of our
Lord One thousand eight hundred and sixty-two.
ALFRED NOBLE. (L.S.)