IMPROVEMENTS IN THE PURIFICATION OF COAL Gas
Year: 1875

page_text: LETTERS PATENT to Henry Young Darracott Scott, of Ealing, in the
County of Middlesex, Major-General, O.B., for the Invention of
Scaled the 2nd April 1875, and dated the 13th January 1875.
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PROVISIONAL SPECIFICATION left by the said Henry Young Darracott
Scott at the Office of the Commissioners of Patents, with his
Petition, on the 13th January 1875.
I, HENRY YOUNG DARRACOTT SCOTT, of Ealing, in the County of
Middlesox, Major-General, C.B., do hereby declaro tho nature of the said
Invention for "IMPROVEMENTS IN THE PURIFICATION OF COAL Gas," to bo as
follows:-
The object of this Invention is the purification of coal gas in such a
manner as to enable the products arising therefrom to be utilized.
In carrying out my Invention 1 make use of magnesia in lieu of lime
for the purpose of removing the carbonic neid in what I will call purifier
No. 1. As the result of this process I obtain an insoluble carbonate of

page_text: magnesia and a soluble sulphide compound. Calcinod dolomite may, on
account of the magnesia it contains, be substituted for that substanco.
The soluble sulphide compound thus obtained is employed in purifior
No. 2 to break up the bisulphide of carbon and the carbonate of mag-
nesia, which is found in purifier No. 1 ; I stir in with gas liquor. By 5
this means I abstract carbonate of ammonia from the gas liquor, and
also deprive some of the carbonate of ammonia of its carbonic acid, by
which means the gas liquor may be gradually made richer in sulphide of
ammonium, and also be employed in purifier No. 2 for breaking up tho
bisulphide of carbon present in the gas. Thirdly, I abstract in purifier 1
No. 3 the sulphuretted hydrogen from the gas by means of phosphate of
iron, which may be conveniently suspended in liquor from No. 2. I
thus set free phosphoric acid, which will unite with the magnesia
present, and form when gas liquor is employed ammoniacal phosphate of
maguesia. This is a valuable marketable compound. I may however 1
use oxide of iron in the ordinary manner for the removal of the
sulphuretted hydrogen which remains in the gas after the provious
processes.
I wish it to bo understood that I do not confine myself to the exact
method of procedure above described. I may, for instance, combine in 2
onc purifier the removal of the carbonic acid from the gas, the breaking
up of the bisulphide of carbon, and the abstraction of carbonato of
ammonia from the gas liquor. The production of commercial phosphate
of magnesia may also be brought about in the same vessels.
By submitting the carbonate of magnesia and ammonia produced from 2
the gas liquor, bicarbonate of magnesia, to a red heat, the magnesia is
received in a condition fit for reuse in the purifiers, and the carbonate
of ammonia distillod off may be utilized by well-known methods.

page_text: "
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Thirteenth day of January, in the
year of our Lord One thousand eight hundred and seventy-five, in
the thirty-eighth year of Her reign, did, for Herself, Her heirs and
successors, give and grant anto me, the said Henry Young Darracott
Scott, Her special licence that I, the said Henry Young Darracott
Scott, my executors, administrators, and assigns, or such others as
I, the said Henry Young Darracott Scott, my executors, admini-
strators, 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 Ohannel
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN THE
PURIFICATION OF Coal Gas," upon the condition (amongst others) that I,
the said Henry Young Darracott Scott, 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 Henry Young Darracott Scott, do
hereby declare the nature of my said Invention, and in what manner
the same is to be performed, to be particularly described and ascertained
in and by the following statement (that is to say) :-
The object of this Invention is the purification of coal gas in such a
manner as to obviate the disadvantages arising from the production of
large quantities of fetid and useless lime compounds which are difficult
to dispose of. By this improved process the resulting substances may be
utilized.
In carrying out my Invention I make use of magnesia as the chief
absorbent of the carbonic acid arising from the distillation of the coal,
so as in great part or wholly to do away with the use of lime. The
magnesia is used either in dry or in wet purifiers in the same way as lime
is now employed, and it is also employed for decarbonating the ammonia.
which is sometimes used on freeing the gas from sulphur compounds in
its subsequent treatment in scrubbers or other washing apparatus.

page_text: The magnesia used in my process may be obtained either by calcination
in tho ordinary manner or by precipitation from a salt of magnesia.
After passing the gas through magnesia purifiers it may, if desired, bo
treated by any of the methods now practised in purifying gas. The
carbonate of magnesia produced in this process is utilized in the
extraction of carbonate of ammonia from gas liquor, according to a pro-
cess for which Letters Patent, dated Thirteenth July, One thousand
eight hundred and seventy-four, No. 2450, have already been granted to
mc, the double salt produced being employed for the manufacture of bi-
carbonate of ammonia or carbonate of ammonia, or after decomposing
the carbonate with a mineral acid, such as sulphuric acid, for the pro-
duction of a manure. The carbonate of magnesia being however mixed
with some sulphide of magnesium it is better to wash that substance
from it (before using it for the extraction of carbonate of ammonia from
ammoniacal liquids) by decomposing the sulphide with sulphate or
phosphate of iron, which will lead to the formation of sulphate and
phosphate of magnesia, both these salts being capable of utilization by
well-known methods. The sulphide of iron, which also results from the
decomposition, will by oxydation supply sulphate of iron, which may be
used in the process just above mentioned. All these actions and reactions
are well understood by chemists, and form no part of my present
Invention.
If it be required to employ sulphide of ammonium for the extraction
of sulphur compounds the employment of magnesia in the washing
liquor will by removing carbonic acid constantly increase the proportion
in it of sulphide of ammonium and freo ammonia, and will enable the
carbonate of ammonia which is absorbed by the carbonate of magnesia
to be removed in a very portable form.
By submitting the carbonate of magnesia and ammonia thus pro-
duced to a red heat the magnesia is recovered in a condition fit for
reuse in the purifiers, and the carbonate of ammonia distilled off can bo
utilized in various well-known ways.
Having now described my Invention of "Improvements in the Puri-
fication of Coal Gas," and having explained the manner of carrying the
same into effect, I wish it to bo understood that what I claim as the
Invention secured to me by the above in part recited Letters Patent is,

page_text: purpose
the employment of magnesia in the purification of coal gas for the
of removing carbonic acid gas therefrom, as herein set forth.
In witness whereof, I, the said Henry Young Darracott Scott, have
hereunto set my hand and seal, the Thirteenth day of July, in
the year of our Lord One thousand eight hundred and seventy-
five.
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