IMPROVEMENTS IN THE TREATMENT OF SULPHATE OF ALUMINA, AND IN OBTAINING ALUM
Year: 1858

page_text: LETTERS PATENT to Alexander Angus Croll, of Coleman Street, in the
City of London, Engineer, for the Invention of "IMPROVEMENTS IN THE
TREATMENT OF SULPHATE OF ALUMINA, AND IN OBTAINING ALUM."
Scaled the 9th August 1858, and dated the 18th May 1858.
PROVISIONAL SPECIFICATION left by the said Alexander Angus Croll
at the Office of the Commissioners of Patents, with his Petition, on the
18th May 1858.
I, ALEXANDER ANGUS CROLL, of Coleman Street, in the City of London,
Engineer, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN THE TREATMENT OF SULPHATE OF ALUMINA, AND IN OBTAINING ALUM,"
to be as follows:-
The improvements relate to means of preparing uncrystallized sulphate of
alumina.
In the preparation of such sulphate of alumina I employ as small a quantity
of acid as possible, and I then neutralize any remaining free acid by adding to
the preparation soda or potash in an alkaline state.
Heretofore alum has been produced by a combination with the sulphate of
alumina of either sulphate of ammonia or of sulphate of potash in certain pro-
portions adapted to produce the best crystals.

page_text: And my improvements cousist, secondly, in substituting to a large extent
for the sulphate of ammonia or potash thus employed, sulphate of soda as a
much less costly article, and only using a small proportion of the sulphate of
ammonia or potash.
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 18th November 1858.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
ANGUS CROLL, of Coleman Street, in the City of London, Engineer, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Eighteenth day of May, in the year of our Lord One
thousand eight hundred and fifty-eight, in the twenty-first year of Her reign,
did, for Herself, Iler heirs and successors, give and grant unto me, the said
Alexander Angus Croll, Her special licence that I, the said Alexander Angus
Croll, my executors, administrators, and assigns, or such others as I, the
said Alexander Angus Croll, 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 "IMPROVE
MENTS IN THE TREATMENT OF SULPHATE OF ALUMINA, AND IN OBTAINING ALUM,"
upon the condition (amongst others) that I, the said Alexander Angus Croll,
my executors or administrators, by an instrument in writing under my, or
their, or one of their hands and seals, should particularly describe and ascer-
tain 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 Augus 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 relate to means of preparing uncrystallized sulphate of
alumina. In the preparation of such sulphate of alumina I employ as small
a quantity of acid (oil of vitriol) as possible, and I then neutralize any

page_text: remaining free acid, as well as decompose any salt of iron, which it may con-
tain, by adding to the preparation soda or potash in an alkaline state, and I
prefer to add such alkali in proportion equal to one-fifth of the resulting
quantity obtained.
Heretofore alum has been produced by a combination with the sulphate of
alumina of either sulphate of ammonia or of sulphate of potash in certain
proportions adapted to produce the best crystals.
And my improvements consist, secondly, in substituting for the sulphate of
ammonia or potash thus employed, sulphate of soda as a much less costly
article, and only using a small proportion of the sulphate of ammonia or
potash. For this purpose, in place of the quantity of sulphate of ammonia or
potash usually employed, I use in carrying out my improvements a proportion
of sulphate of soda equal to about one-fifth part of such quantity, adding
thereto four-fifths or thereabouts of sulphate of ammonia or potash to make
up that quantity.
In witness whereof, I, the said Alexander Angus Croll, have hereunto set
my hand and seal, this Eighteenth day of November, in the year of
our Lord One thousand eight hundred and fifty-eight.
Witness,
W. BROOKES,
73, Chancery Lane, London,
Patent Agent.
A. ANGUS CROLL. (L.S.)