AN IMPROVED PROCESS FOR THE MANUFACTURE OF RED SULPHIDE OF MERCURY
Year: 1875

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane,
in the County of Middlesex, Patent Agent, for the Invention of
"AN IMPROVED PROCESS FOR THE MANUFACTURE OF RED SULPHIDE OF
MERCURY." -A communication from abroad by William Jules
Samuel Grawitz, of Paris, France.
Sealed the 16th October 1875, and dated the 30th April 1875.
PROVISIONAL SPECIFICATION left by the said Alexander Melville
Clark at the Office of the Commissioners of Patents, with his
Petition, on the 30th April 1875.
I, ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, do hereby declare the nature of
the said Invention for "AN IMPROVED PROCESS FOR THE MANUFACTURE OF
RED SULPHIDE OF MERCURY," to be as follows :—-
This Invention relates to an improved process of manufacturing the
red sulphide of mercury. This process consists in dissolving, without
the aid of heat and whilst protected from the action of light, cither
the binoxides of mercury or the salts of the binoxide of mercury in a
soluble hyposulphite.

page_text: When employing the binoxides of mercury it is preferable to add
to the liquor a small quantity of chloride of ammonium, or of a weak
acid to prevent it becoming too alkaline. When the dissolution is
complete the temperature of the solution is gradually raised, whereupon
sulphide of mercury (the red modification) is deposited, the tints of
which vary from orange red to crimson red violet. The precipitate
after having been washed is then brightened by soda and nitric acid.
The color obtained in the above manner resists alike the action of
light, heat, or acids.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Alexander Melville Clark, in the Great Seal Patent
Office on the 30th October 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Thirtieth day of April, 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 unto me, the said Alexander Melville Clark, Her special
licence that I, the said Alexander Melville Clark, my executors, admini-
strators, and assigns, or such others as I, the said Alexander Melville
Clark, 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 "AN
IMPROVED PROCESS FOR THE MANUFACTURE OF RED SULPHIDE OF MERCURY,"
a communication to me from abroad by William Jules Samuel
Grawitz, of Paris, France, upon the condition (amongst others), that I,
the said Alexander Melville Clark, 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
99

page_text: six calendar months, next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said Alexander Melville Clark, 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, that is to say :-
This Invention relates to an improved process of manufacturing red
sulphide of mercury. This process consists in dissolving without the
aid of heat, and whilst protected from the action of light, either bin-
oxides of mercury or the salts of binoxides of mercury in an aqueous
solution of a soluble hyposulphite.
When binoxide of mercury is employed it is preferable to add to the
liquor a small quantity of chloride of ammonium, or of a weak acid to
prevent the liquor becoming too alkaline. When tho solution is com-
plete the temperature is gradually raised, whereupon sulphide of mercury
(the red modification) is deposited, the tints of which vary from orange
red to crimson red violet. The precipitate after having been washed is
then brightened by washing with soda and nitric acid.
The color obtained in the above manner resists the action of light,
heat, or acids.
Having described the nature of the Invention, and the manner of
performing the same, I declare that what I claim as the Invention
to be protected by the herein-before in part recited Letters Patent is,
the manufacture of red sulphide of mercury by the reaction hercin-before
specified, that is to say, by dissolving (without the aid of heat) either
binoxides of mercury, or the salts thereof, in a solution of a soluble
hyposulphite, and precipitating red sulphide of mercury by gradually
raising the temperature, as described.
In witness whereof, I, the said Alexander Melville Clark, have
hereunto set my hand and seal, this Thirtieth day of October,
-
· in the year of our Lord One thousand eight hundred and seventy.