IMPROVEMENTS IN THE MANUFACTURE OR PREPARATION OF MATERIAL FOR THE PURIFICATION OF GAS
Year: 1864

page_text: LETTERS PATENT to Alexander Angus Croll, of Coleman Street, in the
City of London, Civil Engineer, for the Invention of "IMPROVEMENTS IN
THE MANUFACTURE OR PREPARATION OF MATERIAL FOR THE PURIFICATION OF
GAS."
Sealed the 10th Jannary 1865, and dated the 14th July 1864.
PROVISIONAL SPECIFICATION left by the said Alexander Angus Croll at
the Office of the Commissioners of Patents, with his Petition, on the
14th July 1864.
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 OR PREPARATION OF MATERIAL FOR THE
PURIFICATION OF GAS," to be as follows:-
The improvements relate to the employment of sulphuric acid in a highly
concentrated state with sawdust or other vegetable matter, the degree of con-
centration of the acid being such as to effect the desired carbonization of the
fibre without subsequent heating for that purpose.
Sulphuric acid has heretofore been combined in various strengths of solution
with vegetable matters, and the carbonization of the fibre has subsequently
been obtained by raising the temperature of the combination by after heating
processes; but, to the best of my belief, sulphuric acid has not heretofore been
combined with sawdust or other vegetable matter at a degree of concentration
sufficient without subsequent heat to produce the charring of the fibrous
matter. I prefer to employ sulphuric acid of a specific gravity of about

page_text: 1700° or higher, and to combine it in the proportion of 2 parts by weight
thereof to 1 by weight of sawdust. The matters thus obtained are to be used
in what are known as dry lime purifiers. By these means a larger amount
of acid is absorbed by a given amount of vegetable material than by the
process heretofore adopted rendering the combination more effectual, whilst
the residual product is of greater value as a manure.
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 14th January 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 Fourteenth day of July, in the year of our Lord
One thousand eight hundred and sixty-four, 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, 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 "IMPROVEMENTS IN THE MANUFACTURE OR PREPARATION OF MATERIAL
FOR THE PURIFICATION OF GAS," 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 par-
ticularly 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 relate to the employment of sulphuric acid in a highly

page_text: concentrated state with sawdust or other vegetable matter, the degree of con-
centration of the acid being such as to effect the desired carbonization of the
fibre without subsequent heating for that purpose.
Sulphuric acid bas heretofore been combined in various strengths of solution
with vegetable matters, and the carbonization of the fibre has subsequently
been obtained by raising the temperature of the combination by subsequent
heating. In carrying out my improvements I prefer to employ sulphuric acid
of a specific gravity of about 1.700" or higher, at a temperature of about 270°
Fahrenheit, or at such a temperature as can be obtained having reference to
the degree of concentration of the acid employed, and to combine it in the
proportion of about 2 parts by weight thereof to 1 part by weight of dry
sawdust, but varying the proportion with the absorbing power of the sawdust.
I, however, use by preference sawdust obtained from soft wood, or such as
possesses the largest absorbing power. The matters thus obtained are to be
used in what are known as dry lime purifiers.
Having thus described my Invention, I would have it understood that I do
not confine myself to the precise details given, as these may be varied; but
what I claim is, the manufacture or preparation of material for the purification
of gas, substantially as described.
In witness whereof, I, the said Alexander Angus Croll, have hereunto
set my hand and seal, this Thirteenth day of January, in the year of
our Lord One thousand eight hundred and sixty-five.
A. ANGUS CROLL. (L.8.)