IMPROVEMENTS IN OCHRE PIGMENTS
Year: 1882

page_text: LETTERS PATENT to John Macdonald Cameron, of No. 52, Lime Street, in
the City of London, for an Invention of "IMPROVEMENTS IN OCHRE
PIGMENTS."
PROVISIONAL SPECIFICATION left by the said John Macdonald Cameron
at the Office of the Commissioners of Patents on the 13th January 1882.
JOHN MACDONALD CAMERON of No. 52 Lime Street in the City of London.
"IMPROVEMENTS IN OCHRE PIGMENTS."
My Invention relates to the treatment of yellow ochres by a simple and
inexpensive process whereby pigments of greatly improved color are produced.
In carrying out my Invention I take the carbonates or bi-carbonates of the
alkalies, such as potash and soda and soda ash and mix them very intimately with
the ochres to be treated. By this means the oxides of iron are converted into
compounds of a lighter and more brilliant tint than they posses in the unprepared
ochres.
The proportion of the carbonates or bi-carbonates to be added to the ochres will
vary very considerably according to the nature of the ochres and the tint or degree
of brilliancy desired to be obtained, but I have found that the admixture of 75 parts
of the carbonates or bi-carbonates with 100 parts of ochre gives a very satisfactory
result, but I in no way limit myself to these proportions.
The said substances require to be ground very intimately together in order to
produce the result above stated.
Similar results are also obtained though of varying intensity of tint, by the
substitution of the hydrated oxides and the oxalates, chlorates and chlorides of the
alkali metals; also by the use of oxalic, carbonic, hydrochloric and nitric acids, and
in a minor degree by the alums and the carbonates, chlorides and oxalates of the
alkaline earths such as lime and magnesia.
'
The color can also be improved by the admixture of varying quantities of
chromate and bi-chromate of potash according to the depth of tint required..
By digesting the ochres with solutions of the above substances, filtering, drying
and pulverising, similar results to those above stated are obtained.
"
Should the "
body" or 'covering power" of the ochre be diminished by
treatment of any of the above substances, I add china clay or any of the other
white clays of commerce, sulphate or carbonate of barium or sulphate or carbonate
of lime in such proportions as I may deem requisite.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Macdonald Cameron in the Great Seal Patent Office on the
8th July 1882.
JOHN MACDONALD CAMERON of No. 52 Lime Street in the City of London.
"IMPROVEMENTS IN OCHRE PIGMENTS.'
"
My Invention relates to the treatment of yellow ochres by a simple and
inexpensive process whereby pigments of greatly improved colour are produced.
In carrying out my Invention I take the carbonates or bi-carbonates of the
alkalies such as potash and soda and soda ash and mix them very intimately with
the ochres to be treated. By this means the oxides of iron are converted into
compounds of a lighter and more brilliant tint than they possess in the unprepared
ochres. The proportion of the carbonates or bi-carbonates to be added to the
ochres will vary very considerably according to the nature of the ochres and the
tint or degree of brilliancy desired to be obtained, but I have found that in treating
strong English ochres the admixture of 75 parts of the carbonates or bi-carbonates
with 100 parts of ochre gives a very satisfactory result, but I in no way limit
myself to these proportions.
The said substances require to be ground very intimately together in order to
produce the result above stated.
Similar results are also obtained though of varying intensity of tint, by the
substitution of the oxalates of the alkali metals; also by the use of oxalic and
carbonic acids and by treating the ochres with solutions of the yellow salts of
chromic acid. By digesting the ochires with solutions of the above substances,
filtering, drying and pulverising, similar results to those above stated are obtained.
In employing carbonic acid for the purposes of my Invention, the gas may
either be applied in a free state to the ochres in a moist condition, by any known
means whereby the ochres can be made to absorb the gas or I pass the gas into
water containing the ochres in suspension. The ochre pigments may be treated
with the above substances either singly or with any two or more in combination.
Should the "body' or "covering power" of the ochre be diminished by
treatment with any of the above substances, I add china clay or any of the other
white clays of commerce, sulphate or carbonate of barium or sulphate or carbonate
of lime in such proportions as I may deem requisite.
"
Having thus described the nature of my Invention and in what manner the same
is to be performed, I claim:
The herein described improved manufacture of ochre pigments by combining
ochres with any one or more of the following substances namely: The carbonates
or bi-carbonates of the alkalies, soda ash, the oxalates of the alkalies; oxalic or
carbonic acid and the yellow salts of chromic acid.
In witness whereof I the said John Macdonald Cameron have hereunto set
my hand and seal this Eighth day of July in the year of our Lord One
thousand eight hundred and eighty two.