IMPROVEMENTS IN THE PURIFICATION OF GAS."
Year: 1860

page_text: LETTERS PATENT to Alexander Angus Croll, of Coleman Street, in the
City of London, Engineer, for the Invention of "IMPROVEMENTS IN
THE PURIFICATION OF GAS."
PROVISIONAL SPECIFICATION left by the said Alexander Angus Croll
at the Office of the Commissioners of Patents, with his Petition, on the
8th June 1860.
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 PURIFICATION OF GAS," to be as follows:-
The improvements consist in the use of shale or spent shale, or other
aluminous matters; combined or saturated with sulphuric acid, and placed in
dry lime purifiers in the purification of gas.
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 8th December 1860.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
ANGUS CROLL, of Coleman Street, in the City of London, Engineer, send
5 greeting.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent bearing date the Eighth day of June, in the year of our Lord
One thousand eight hundred and sixty, in the twenty-third 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 "IMPROVE-
MENTS IN 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 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 consist in the use of shale or spent shale or other
aluminous matters, combined or saturated with sulphuric acid, and placed in
dry lime purifiers in the purification of gas.
But that the nature of the Invention may be fully understood, I will proceed
to describe the means pursued by me.
I take alum shale, and when such has been roasted, as for the manufacture
of alum, I mix it in a dry state with sulphuric acid, and, by preference, in
about equal proportions thereof, the sulphuric acid used containing say
80 per cent. or thereabouts of oil of vitriol of commerce. In obtaining the
combination I mix the dry shale, as stated, in about an equal quantity of the
sulphuric acid, at a temperature of about 220 degrees Fahrenheit. It is,
however, desirable in adding the acid that care be taken thoroughly to mix it
and the shale together until the acid has cooled down, so as to prevent their
solidifying into a compact mass, otherwise the combination obtained will
require to be broken up or reduced by the action of edge runners or other
suitable means. The most suitable form of the compound I consider to be
that when it is in separate granules or portions of about the size of peas. The

page_text: compound thus obtained I place in apparatus of the character of those
generally known as dry lime purifiers, and I pass the gas to be purified
through such purifiers, so as to be thoroughly acted upon by the composition,.
and I continue so to use such material, until, by testing, the gas after passing.
it through such purifying material, I find that the material has become spent.
I use as a test turmeric or reddened litmus paper, as is well understood. A
similar effect may also be obtained by using pipe clay as prepared for the
manufacture of alum, and treating it by sulphuric acid, as above stated in
relation to shale.
A beneficial effect may also be obtained by using the spent shale which has
been employed in the manufacture of alum.
Having thus described the nature of my Invention, and the means which
I adopt in carrying the same into effect, I would have it understood that I do
not confine myself to the precise proportions stated, nor do I claim the use of
alum or sulphate of alumina when either is used by itself; but what I do
claim is the use of shale or spent shale, or other aluminous matter, combined
or saturated with sulphuric acid, in the purification of gas, substantially as
explained.
In witness whereof, I, the said Alexander Angus Croll, have hereunto
my hand and seal, this Seventh day of December, in the year of
our Lord One thousand eight hundred and sixty.
Witness,
WILLIAM BROOKES,
73, Chancery Lane, London,
Patent Agent.
A. ANGUS CROLL. (L.8.)