IMPROVE- MENTS IN THE MANUFACTURE OF A RED PIGMENT, COMMONLY CALLED VENETIAN RED
Year: 1853

page_text: LETTERS PATENT to John Oliver, of the Borough of Newcastle-upon-
Tyne, Manufacturing Chymist, for the Invention of " IMPROVE-
MENTS IN THE MANUFACTURE OF A RED PIGMENT, COMMONLY CALLED
VENETIAN RED."
Sealed the 17th May 1853, and dated the 16th March 1853.
PROVISIONAL SPECIFICATION left by the said John Oliver at the
Office of the Commissioners of Patents, with his Petition, on the
16th March 1853.
I, JOHN OLIVER, of the Borough of Newcastle upon Tyne, Manufac-
turing Chymist, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN THE MANUFACTURE OF A RED PIGMENT, COMMONLY
CALLED VENETIAN RED," to be as follows:-
This Invention consists in decomposing a solution of chloride of iron,
by calcined magnesian limestone, also in decomposing the chloride of
magnesium in the supernatant solution of chloride of calcium and
magnesium, by means of calcined magnesian limestone, forming a
solution of chloride of calcium, and precipitating hydrate of magnesia:
Also in decomposing a solution of sulphate of iron by means of the
hydrate of magnesia obtained as described, by which means oxide of
iron precipitated is obtained, and sulphate of magnesia in solution: Also

page_text: in decomposing a solution of sulphate of iron by a solution of chloride of
barium, by which means I obtain precipitated sulphate of baryta, and
chloride of iron in solution.
The precipitated oxide of iron is separated from the supernatant
solution of chloride of calcium and magnesium by filtration or any
other convenient method. Then, by repeated washings, are removed all
traces of saline matter from the oxide of iron. A proportionate quantity
of calcined gypsum is mixed with the oxide of iron, and they are
ground with water, or otherwise, previous to the conversion into Venetian
red by calcination. After having submitted the mixed oxide of iron and
gypsum to the grinding process, any excess of water is removed, the
matters are driod, and they are then calcined in a close retort.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Oliver, in the Great Seal Patent Office, on
the 16th September 1853.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
JOHN OLIVER, of the Borough of Newcastle upon Tyne, Manufacturing
Chemist, send grecting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Sixteenth day of March, in the year
of our Lord One thousand eight hundred and fifty-three, in the six-
teenth year of Ier reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said John Oliver, Her special licence that
I, the said John Oliver, my executors, administrators, and assigns, or
such others as I, the said John Oliver, 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 OF A
RED PIGMENT, COMMONLY CALLED VENETIAN RED," upon the condition
(amongst others) that I, the said John Oliver, by an Instrument in
writing under my hand and seal, should particularly describe and
ascertain the naturo of the said Invention, and in what manner the

page_text: 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 John Oliver, 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):
This Invention consists in decomposing a solution of chloride of iron by
calcined magnesian limestone, also in decomposing the chloride of magne-
sium in the supernatant solution of chloride of calcium and magnesium,
by means of calcined magnesian limestone, forming a solution of chloride
of calcium, and precipitating hydrate of magnesia: Also in decom-
posing a solution of sulphate of iron, by means of the hydrate of
magnesia obtained as described, by which means oxide of iron precipi-
tated is obtained, and sulphate of magnesia in solution: Also in
decomposing a solution of sulphate of iron, by a solution of chloride of
barium, by which means I obtain precipitated sulphate of baryta, and
chloride of iron in solution.
The precipitated oxide of iron is separated from the supernatant
solution of chloride of calcium and magnesium by filtration or any
other convenient method. Then, by repeated washings, are removed all
traces of saline matter. From the oxide of iron a proportionate quantity
of calcined gypsum is mixed with the oxide of iron, and they are
ground with water, or otherwise, previous to the conversion into Venetian
red by calcination. After having submitted the mixed oxide of iron and
gypsum to the grinding process, any excess of water is removed, the
matters are dried, and they are then calcined in a close retort.
Having thus stated the nature of my Invention, I will proceed to
describe the means of performing the same. I decompose a solution of
chloride of iron, by means of calcined magnesian limestone, or magnesia
stone. For this purpose I put into any convenient vessel the mixed
hydrate of lime and magnesia in the consistence of a thick cream. T
gradually pour in a solution of chloride of iron (which may be obtained
in any convenient manner; I prefer to obtain it by dissolving iron in
muriatic acid, or by decomposing a solution of sulphate of iron with a
solution of chloride of barium, as herein-after described). constantly

page_text: stirring the mixture, until the whole of the mixed hydrates are con-
verted into the chlorides of calcium and magnesium, to insure which I
prefer using a slight excess of chloride of iron. I then allow the
hydrated oxide of iron to subside, and which I employ in the manufac-
ture of Venetian red as hereafter described; after which I remove the
supernatant solution of chloride of calcium and magnesium by filtration
or any other convenient method, and remove all traces of chloride from
the hydrated oxide of iron by repeated washings. I would remark, that
as magnesian stone or magnesian limestone varies in the relative pro-
portions of the magnesia and lime composing it, I prefer to use such
as are composed in the relation of 48 per cent. of carbonate of
magnesia, and 52 per cent. of carbonate of lime; but I do not confine
myself thereto.
With regard to the chloride of magnesium present in the supernatant
solution resulting from the above process, I decompose it by means of
calcined magnesium limestone, for which purpose I add to the mixed
chlorides of calenum and magnesium an equivalent quantity of calcined
magnesian limestone, thus forming chloride of calcium in solution, and
precipitating hydrate of magnesia. After the hydrate of magnesia has
subsided, I draw off the supernatant liquor, and remove all traces
of chloride of calcium from the hydrate of magnesia by repeated
washings.
To the hydrate of magnesia thus obtained I add a warm solution
(preferring a concentrated solution) of sulphate of iron, forming a solu-
tion of sulphate of magnesia, and precipitating hydrated oxide of iron,
which I use in the manufacture of Venetian red, as hereafter explained.
It is better to use sulphate of iron in this process somewhat in excess.
Or to the bydrate of magnesia, obtained as above, I add a solution of
chloride of iron, as explained in the first process, forming a solution
of chloride of magnesium, and precipitating hydrated oxide of iron,
which I use in the manufacture of Venetian red, as hereafter explained.
I obtain chloride of iron, dissolving iron in muriatic acid, or in the
following manner-To a boiling solution of chloride of barium in any
convenient vessel, I add a boiling solution of sulphate of iron, until the
whole of the barytes is precipitated; thus obtaining a solution of chloride
of iron, as before mentioned.

page_text: In making hydrated oxide of iron into Venetian red, I add from three
to four parts of calcined gypsum in powder to each one part by weight
of the iron present in the oxide, according to the colour required; the
lesser portion of gypsum when a deep shade of colour is desired. And in
place of calcining the mixture as heretofore, and then to grind the pro-
duct, I proceed to wash and grind the mixture previous to calcining the
same, for which purpose I introduce the mixture, with water, into the
usual livigating tub, and continue the grinding process for ten or twelve
hours; the matters are then run into settlers, and allowed to subside;
the water is run off, and the mass dried upon flues, or by any con-
venient method.
The dried and ground mixture is next to be calcined, which I do in
a retort closed from the fire in such manner as to prevent the deposition
of impurities from the fire upon the compound during the calcination,
and at the same time allow the free admission of air upon the incan-
lescent mass. I prefer these retorts to be of fire-clay, externally
heated, and consequently closed from the fire, though open to the
admission of air, though other forms of retort may be used if they be
closed from the fire.
Having thus described the nature of my said Invention, and the
manner of performing the same, I would have it understood that I do
not confine myself to the precise details as herein described; but I
claim the combined means, herein described, of manufacturing Venetian
red; and also the decomposing sulphate of iron by magnesia, and apply
the hydrated oxide so obtained of iron to the manufacture of Venetian
red.
In witness whereof, I, the said John Oliver, have hereunto set my
hand and seal, this Fifteenth day of September, in the year of
our Lord One thousand eight hundred and fifty-three.
JOHN OLIVER. (L.S.)
Witness, S. CARPMAEL.