IMPROVEMENTS IN PIGMENTS, AND IN THE PREPARATION OF THE SULPHATES OF IRON AND MAGNESIA
Year: 1840

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"GREGSON'S SPECIFICATION.
TO ALL TO WHOM THESE PRESENTS. SHALL COME, ".I,- JOHN
BRUMWELL GREGSON; of. Newcastle-upon-Tyne, in the County of Northum
berland; Soda Water Manufacturer, send greeting.
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WHEREAS Her present most Excellent Majesty, Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing, date. at
Westminster, the, Twenty-third day of December,, in the fourth year of Her
reign, did, for Herself, Her heirs and successors; ¡give and grant. unto me, the
said John Brumwell Gregson, my exors, admors, and assigns, Her especial
licence, full power,sole privilege and authority, that I, the said. John
Brumwell Gregson, mysexors, admors, and assigns, and such others; as I, the
said John, Brumwell Gregson; my exors, adiñors,' or 'assigns, should at any
time agree with; and no others; from time and time, and at all times; during
the term of years therein expressed; should and lawfully might make, use,
exercise, and vend, within that part of Her Majesty's United Kingdom. of
Great Britain and Ireland called England, Her Dominion of Wales, Town of
Berwick-upon-Tweed, the Islands of Guernsey, Jersey, Alderney, Sark, and
Man, and also in all Her Majesty's Colonies and Plantations abroad, my
Invention of "IMPROVEMENTS IN PIGMENTS, AND IN THE PREPARATION OF THE
SULPHATES OF IRON AND MAGNESIA;" in which said Letters Patent is contained a
proviso that I, the said John Brumwell Gregson, shall cause a particular
description of the nature of my said Invention, and in what manner the same
is to be performed, to be inrolled in Her said Majesty's High Court of

page_text: Chancery within six calendar months next and immediately after the date of
the said in part recited Letters Patent, as in and by the same, reference being
thereunto had, will more fully and at large appear.
NOW KNOW YE, that, in compliance with the said proviso, I, the said
John Brumwell Gregson, do hereby declare the nature of my Invention to
consist in,-
First, the preparation of the red pigment called "Venetian red," by an
improved method or methods.
Second, the preparation of a black pigment not hitherto made or in use.
Third, an improved mode of making copperas or the sulphate of iron.
And,
Fourth, an improved mode of making sulphate of magnesia.
And I declare that the manner in which the said Invention is to be per-
formed is as follows, that is to say :-
With respect to the first part of my Invention, namely, the improvement in
the manufacture of Venetian red, the same consists,-firstly, in the application
of oxide of iron obtained from chloride of iron; and, secondly, in the con-
version of the sulphurous acid which is given off during the calcination of
sulphate of iron with gypsum, or sulphate of lime into sulphuric acid. And,
firstly, as to the application of oxide of iron, I gradually pour into any con-
venient vessel, containing hydrate of lime in the state of cream of lime, a
solution of chloride of iron, constantly stirring the mixture until all the lime is
'converted into chloride of calcium, to insure which I use an excess of chloride
of iron. I then wash the oxide of iron thus obtained with water, in order to
free it from the chloride of calcium; after which it is to be dried, and mixed
with about two or three times it's weight of gypsum of sulphate of lime in
powder, and the mixture exposed to a red heat in a reverberatory furnace for
the space of about half an hour, or until it assumes the well-known colour of
Venetian red. It is then to be removed from the furnace, ground very fine
with a pair of horizontal or edge stones, and sifted in the usual manner. And
with respect to the conversion of the sulphurous acid, I declare, that whereas
in the ordinary process of making Venetian red from sulphate of iron, and
gypsum or sulphate of lime, these substances, in about equal proportions, are
calcined in a reverberatory furnace for seven or eight hours, or until the whole
of the sulphate of iron is decomposed, and the sulphurous acid which is given
off is dissipated along with the carbonaceous matter of the fuel into the
atmosphere. Now, in order to convert such sulphurous acid into sulphuric
acid, I cause the decomposition to take place in a retort, or other suitable
vessel; and I pass a current of atmospheric air or steam through such retort

page_text: or vessel. The apparatus which I prefer to employ for this purpose consists
of a retort placed vertically in a suitable furnace, and having at its upper end
an aperture through which the mixed sulphates may be introduced, and a pipe
for conveying off the sulphurous acid connected with a vitriol chamber, and
at its lower end a pipe, by which atmospheric air or steam may be introduced,
and an aperture through which the materials may be withdrawn. Having
closed the lower end of the retort, I introduce gypsum or sulphate of
lime in small pieces, to occupy a portion of the bottom of the retort. I then
nearly fill the retort with the mixed sulphates, and I prefer the sulphate of
iron to be dried and reduced to powder, along with the sulphate of lime. As
soon as these materials become red hot, I close the upper end of the retort,
and force a current of atmospheric air through it by means of a common force
pump, or I connect it with a steam pipe, and cause steam to rush through it.
The air or steam in its passage carries along with it the sulphurous acid
through the tube in the upper end of the retort into the vitriol chamber,
which is there converted into sulphuric acid, as in the ordinary process of
making oil of vitriol. When the sulphate of iron is nearly or entirely decom-
posed, I remove it from the retort, throw it into water, grind and wash'd in the
usual manner.
With respect to the second part of my Invention, namely, the preparation
of a black pigment not hitherto made or in use, my method is this:-I take
any quantity of oxide of iron obtained from the chloride by means of lime, as
before described, or as it is found to exist in certain clays or ochres, or as it
may be prepared by various other processes. I introduce into a retort,
resembling an ordinary gas retort (but much lighter in its construction, having
at its closed end a small perforation of about a quarter of an inch in diameter),
the oxide of iron, either pure, or as contained in certain clays or ochres, or
mixtures of both, reduced to a fine powder. I then place the retort either
vertically or horizontally in a suitable furnace, and as soon as it is red hot, I
remove it from the furnace, and, closing the mouth of the retort, I attach a
pipe to it, and force, by means of an air pump, hydrogen gas or carburetted
hydrogen gas through it, until inflammable gas issues out at the perforation at
the end of the retort. I then close the perforation, and keep the materials
entirely free from contact with atmospheric air until cold. The oxide of iron
is thus converted into the protoxide of iron, which forms
and is prepared for use by grinding and washing as usual.
the black pigment,
With respect to the third part of my Invention, which relates to my
inproved manner of making copperas or sulphate of iron, I take the slag or
refuse abundantly produced in the balling furnaces of iron works, which is a

page_text: compound of sillica and oxide of iron, and reduce it to a very fine powder.
Into a shallow vessel, lined with lead, and capable of. holding about fifty
gallons, I put about one hundred pounds' weight of this finely-pounded slag or
silicate of iron, made into a thin paste with water. I then gradually add
about one hundred pounds. weight of sulphuric acid of commerce, of about the
specific gravity of 1-845, previously diluted with its own weight of water; and
during the addition of the dilute noid I keep constantly stirring the mixture.
The sulphuric acid combines rapidly with the oxide of iron. with the production
of much heat; and, when 'cold, I obtain a. solid mass of impure sulphate of
iron. This impure sulphate of iron: is dissolved in about its own weight of 1
water; and the solution allowed to stand-till clear, after. which it is to be
drawn off; evaporated, and crystallized in. the usual manner... The sediment
may be washed with more water to free it .entirely from sulphate of iron,.and
the-washings, evaporated and crystallized in the same manner.
T
With respect to the fourth. and last. part. of my Invention, namely, an
improved mode of-making sulphate of magnesia, I proceed as follows:- Into
a retort resembling. a gas retort; and set in. a furnace in the same manner, I
introduce about one hundred pounds of magnesian limestone in; fine powder,
and keep it at a low red heat for two or three hours, or until it. ceases,; or
nearly so, to give off carbonic acid gas: (which rat: that temperature is expelled
from the carbonate of magnesia only), and which may be known by causing a..
pipe, connected with the mouth of the retort,, to dip into a vessel.of water...,It
must then be removed from the retort and allowed to cool. I dissolve, in an
iron boiler, about one hundred pounds of crystallized sulphate of iron, in, about
three or four times its weight of water, and then stir.in the calcined magnesian
imestone, and boil the mixture for about one. hour, when, by the reaction of
the magnesia, the sulphate of iron is decomposed,. and sulphate of magnesia. is
formed: The solution must now be tested with prussiate. of potash;. and
should it be found to contain iron, a further addition of calcined magnesian
limestone must be made, until the iron is entirely precipitated. The oxide of
iron and carbonate of lime must be allowed to subside, and the clear 'solution
of sulphate of magnesia drawn off, and evaporated.and crystallized. The sedi
ment may be further washed to remove any sulphate of magnesia remaining in
it. It is then to be dried and calcined at a red heat, after which it may be
used as a brown-pigment.
And having now described the nature of my said. Invention, and the manner
in which the same is to be performed; I.declare that. I claim,
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tenon, s
First, the application of oxide of iron, obtained by the action of lime upon
chloride of iron, to-the manufacture of Venetian red, and also the collecting of

page_text: the sulphurous acid evolved in the making of Venetian red by the calcination
of gypsum, or sulphate of lime with sulphate of iron, and the conversion of the
same into sulphuric acid by the method or in the manner herein-before-
described.
Second, the making of a black pigment from oxide of iron by means of
hydrogen gas or carburetted hydrogen gas.
Third, the making of sulphate of iron by dissolving silicate of iron in
sulphuric acid. And,
Fourth, the making of sulphate of magnesia by acting upon calcined
magnesian limestone with sulphate of iron.
In witness whereof, I, the said John Brumwell Gregson, have hereunto
set my hand and seal, this Twenty-second day of June, in the year
of our Lord One thousand eight hundred and forty-one.
JOHN BRUMWELL (L.S.) GREGSON.
AND BE IT REMEMBERED, that on the Twenty-second day of June,
in the year of our Lord 1841, the aforesaid John Brumwell Gregson came
before our said Lady the Queen in Her Chancery, and acknowledged the
Specification aforesaid, and all and every thing therein contained and specified,
in form above written. And also the Specification aforesaid was stamped
according to the tenor of the Statute made for that purpose.
Inrolled the Twenty-third day of June, in the year of our Lord One
thousand eight hundred and forty-one.