IMPROVEMENTS IN THE TREATMENT OF SPENT OXIDE OF IRON FOR THE PURPOSE OF EXTRACTING CYANOGEN COMPOUNDS THEREFROM.
Year: 1874

page_text: LETTERS PATENT to William George Valentin, of the Royal College
of Chemistry, South Kensington, in the County of Middlesex, for
the Invention of "IMPROVEMENTS IN THE TREATMENT OF SPENT OXIDE OF
IRON FOR THE PURPOSE OF EXTRACTING CYANOGEN COMPOUNDS THEREFROM.
PROVISIONAL SPECIFICATION left by the said William George Valentin
at the Office of the Commissioners of Patents, with his Petition,
on the 12th November 1874.
I, WILLIAM GEORGE VALENTIN, of the Royal College of Chemistry,
South Kensington, in the County of Middlesex, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN THE TREATMENT OF
SPENT OXIDE OF IRON FOR THE PURPOSE OF EXTRACTING CYANOGEN COMPOUNDS
THEREFROM," to be as follows:-
This Invention has for its object the utilisation of the cyanogen com-
pounds often found in the materials employed in purifying coal gas
and known as "spent oxide." Hydrated ferric oxide as it comes from
the gas purifiers contains a considerable quantity of sulphur and also

page_text: ammoniacal salts which interfere with the profitable extraction of
cyanogen compounds by means of milk of lime, potash, or soda, as
hitherto practised. The free sulphur is acted upon by these strong bases
with formation of soluble alkaline sulphides or polysulphides, and a
portion of the cyanogen compounds is destroyed, being converted into
sulpho-cyanogen compounds, whilst at the same time the ammonia is
driven off by the action of the caustic alkalies. In order to avoid these
disadvantages I employ the washed "spent oxide" and digest it at the
temperature of boiling water with carbonate of lime (chalk) or with
carbonate of magnesia (magnesite), or, by preference, with slightly
burnt dolomite or magnesian limestone. The insoluble cyanogen com-
pounds which are present in the spent oxide consist principally of ferro-
cyanide of iron or Prussian blue, and can be decomposed more or less
completely by digestion with basic carbonate of magnesia, such as the
commercial magnesia alba, and also by chalk or precipitated carbonate
of lime (although more slowly and not quite so perfectly) without the
free sulphur being injuriously acted upon. It is preferred therefore to
digest the fincly powdered "spent oxide "after the same has been washed
in pans either over open fires or heated by means of jets of steam or
coils of steam pipes together with slightly burnt dolomite or magnesian
limestone, the latter being made into a stiff paste by mixing with water.
The quantity of burnt dolomite necessary for this process must depend
upon the per-centage of ferro-cyanogen present in the "spent oxide,"
but from 5 to 10 parts by weight will usually be found sufficient.
The aqueous solution after filtration contains the ferro-cyanogen, as
ferro-cyanide of calcium or magnesium, or of both, as the case may be,
and constitutes a light yellow very slightly alkaline liquid, which on the
addition of a small quantity of acid and of a salt or salts of iron yields a
precipitate of Prussian blue of a very fine colour, which falls out very
rapidly and is easily washed by decantation and filtration.
The process is equally applicable in the case of "spent oxide" from
which the soluble salts have been removed by water and the sulphur by
extraction with carbon disulphide. The ferric-oxide which is then left
and which usually contains some magnesia salt which has not been
acted upon is considerably improved thereby and can be used over again
with great advantage for the purification of the coal gas.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William George Valentin in the Great Seal Patent
Office on the 11th May 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
GEORGE VALENTIN, of the Royal College of Chemistry, South Kensing-
ton, in the County of Middlesex, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twelfth day of November, in the year
of our Lord One thousand eight hundred and seventy-four, in the thirty-
eighth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said William George Valentin, Her special licence
that I, the said William George Valentin, my executors, administrators,
and assigns, or such others as I, the said William George Valentin, 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 TREATMENT OF SPENT OXIDE OF IRON FOR THE PURPOSE OF EXTRACTING
CYANOGEN COMPOUNDS THEREFROM," upon the condition (amongst others) that
I, the said William George Valentin, 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 William George Valentin, 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:-
My said Invention has for its object the utilization of the cyanogen
compounds often found in the materials employed in purifying coal gas
and known as spent oxide." Hydrated ferric-oxide as it comes from
the gas purifiers contains a considerable quantity of sulphur and also
"

page_text: ammoniacal salts which interfere with the profitable extraction of
cyanogen compounds by means of milk of lime, potash, or soda. The
free sulphur is acted upon by these strong bases with formation of
soluble alkaline sulphides or polysulphides, whilst at the same time the
ammonia is driven off by the action of the caustic alkalies. In order to
avoid these disadvantages I employ the washed "spent oxide" and
digest it at the temperature of boiling water with carbonate of lime
(chalk), or with carbonate of magnesia (magnesite), or by preference,
with slightly burnt dolomite or magnesian limestone. The insoluble
cyanogen compounds which are present in the "spent oxide" consist
principally of ferro-cyanide of iron or Prussian blue, and can be decom-
posed more or less completely by digestion with basic carbonate of
magnesia, such as the commercial magnesia alba, or by slightly burnt
magnesite, and also by chalk or precipitated carbonate of lime (although
more slowly and not quite so perfectly) without the free sulphur being
injuriously acted upon. It is preferred therefore to digest the finely
powdered "spent oxide" after the same has been washed in pans either
over open fires or heated by means of jets of steam or coils of steam
pipes, together with slightly burnt dolomite or magnesian limestone, or
magnesite. The quantity of burnt dolomite or magnesite necessary for
this process must depend upon the per-centage of ferro-cyanogen present
in the " spent oxide," but from 5 to 10 parts by weight will usually be
found sufficient.
Slightly burnt magnesite, hydromagnesite, or other suitable magnesia
mineral may be advantageously employed instead of dolomite for
effecting the decomposition of the ferro-cyanogen compounds. As the
presence of iron oxide in magnesite is not objectionable the cheaper
kinds of magnesite may be used. Unburnt magnesite, or magnesic-
carbonate, as it is found in nature acts but little upon the ferro-cyanogen
compounds even when finely powdered. When slightly burnt it crumbles
readily to a fine dust and decomposes them readily. A mixture of
magnesic-carbonate and oxide, or so called basic-magnesic carbonate, is
thus constituted.
When magnesite is ignited strongly and for a sufficient length of time
to convert it into caustic magnesia, or nearly so, and the "spent oxide"
is digested with it, I have observed that a considerable amount of sulpho-
cyanogen is present in the filtrate, and that caustic magnesia like the
other caustic alkalics acts injuriously and should therefore be avoided.

page_text: The aqueous solution after filtration contains the ferro-cyanogen as
ferro-cyanide of calcium or magnesium, or of both, as the case may be,
and constitutes a very slightly alkaline liquid of a light yellow colour,
and which liquid on the addition of a small quantity of acid and of a
salt or salts of iron yields a precipitate of Prussian blue of a very fine
colour, which falls out very rapidly and is easily washed by decantation
and filtration.
The process is equally applicable in the case of " spent oxide" from
which the soluble salts have been removed by water and the sulphur by
extraction with carbon di-sulphide. The ferric-oxide which is then left,
and which usually contains some magnesia salt which has not been
acted upon, is considerably improved thereby, and can be used over
again with great advantage for the purification of coal gas.
Having thus declared and ascertained the nature of my said Inven-
tion, and in what manner the same is to be performed, I would observe in
conclusion that what I consider novel and original, and therefore claim as
being the Invention secured to me by the said herein-before in part
recited Letters Patent are, tlie process and method of treating "spent
oxide," substantially as and for the purposes herein-before described
and set forth, or any mere modifications thereof.
In witness whereof, I, the said William George Valentin, have here-
unto set my hand and seal, this Tenth day of May, in the
of our Lord One thousand eight hundred and seventy-five.
year