IMPROVEMENTS IN THE MANUFACTURE OF SULPHATE OF ALUMINA
Year: 1865

page_text: LETTERS PATENT to Alexander Angus Croll, of Coleman Street, in the
City of London, Civil Engineer, for the Invention of "IMPROVEMENTS IN
"
PROVISIONAL SPECIFICATION left by the said Alexander Angus Croll
at the Office of the Commissioners of Patents, with his Petition, on the
30th March 1865.
I, ALEXANDER ANGUS CROLL, of Coleman Street, in the City of London,
Civil Engineer, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN THE MANUFACTURE OF SULPHATE OF ALUMINA," to be as
follows:-
The improvements have for their object the obtaining a soluble sulphate of
alumina with increased rapidity, economy, and quantity considered in relation
to the quantities of clay or other aluminous base and of acid under operation,
and the time employed in obtaining the results. For this purpose I take,
say, five parts by weight of oil of vitriol, spec. grav. 1.845, diluted with water
to the sp. gr. of, say, 74 Twaddle, and heated to about 220° Fahrenheit, at
which temperature the specific gravity will show about 65 Twaddle. To this
diluted acid I add about 4 parts by weight of thoroughly dry and finely
divided aluminous clay, which has been previously roasted. These pro-
portions may, however, be varied, dependent in great measure upon the quan-
tity of alumina in the base operated upon, and the heat may be applied to
the aluminous base with cold dilute acid.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Alexander Angus Croll in the Great Seal Patent Office on
the 30th September 1865.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
ANGUS CROLL, of Coleman Street, in the City of London, Civil Engineer, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirtieth day of March, in the year of our Lord
One thousand eight hundred and sixty-five, in the twenty-eighth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Alexander Angus Croll, Her special licence that I, the said
Alexander Angus Croll, executors, administrators, and assigns, or such
others as I, the said Alexander Angus Croll; 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 "IMPROVEMENTS IN THE MANUFACTURE OF SULPHATE OF ALUMINA,"
apon the condition (amongst others), that I, the said Alexander Angus
Croll, executors or administrators, by an instrument 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 Alexander Angus Croll, 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 :-
The improvements have for their object the obtaining a sulphate of alumina
with increased rapidity, economy, and quantity considered in relation to the
quantities of clay or other aluminous base and of acid under operation, and
the time employed in obtaining the results. And my Invention consists in
employing sulphuric acid (oil of vitriol) diluted to a limited extent with
water, and heated to a bigh degree of temperature to act upon the aluminous
base.
In carrying out these improvements I prefer to employ, say, five parts by
weight of oil of vitriol, spec. grav. 1.845, diluted with water to the sp. gr.

page_text: of, say, 74 Twaddle, and heated to about 220° Fahrenheit, at which tem-
perature the specific gravity will shew about 65 Twaddle. To this diluted
acid I add about 4 parts by weight of thoroughly dry and finely divided clay
rich in alumina, and which has been previously roasted. The temperature of
the acid may to some extent be varied, and the proportions given may also be
varied, dependent in great measure upon the quantity of alumina in the base
operated upon. Heat may be applied to the aluminous base when using cold
dilute acid, but I prefer to apply the heat as stated to the acid. The sulphate
of alumina thus obtained may be treated with carbonate of lime as described
in the Specification of a former Patent granted to me, bearing date the Thirtieth
day of September, 1864, No. 2407, in order to yield a cake of sulphate of
alumina; or, if it be desired to obtain a cake free from silica, the solution
may, when chemical action has ceased, be diluted so as to obtain the pre-
cipitation of the silica and undissolved clay which may be contained therein,
and the solution remaining after such precipitation when again concentrated
by evaporation may be treated with carbonate of lime, and yield a good cake
of sulphate of alumina; or, if it be desired to obtain a sulphate of alumina
free from insoluble matter, the above clear liquor, when sufficiently con-
centrated, may be allowed to cool to yield the cake required, or the sul-
phate of alumina obtained by these means may be used in the manufacture
of alum.
Having thus described my improvements, and means which I adopt in
carrying the same into effect, I would have it understood that what I claim
is, the manufacture of sulphate of alumina in manner substantially as
explained.
In witness whereof, I, the. said Alexander Angus Croll, have hereunto
set my hand and seal, this Thirtieth day of September in the year
of our Lord One thousand eight hundred and sixty-five.
A. ANGUS CROLL. (L.S.)