IMPROVEMENTS IN THE MANUFACTURE CHROMATES AND BICHROMATES
Year: 1884

page_text: I WILLIAM JOHN ALEXANDER DONALD of Number Two Belgrave Terrace,
Hillhead Glasgow Secretary and Commercial Manager of The Eglinton Chemical
Company Limited Glasgow in the County of Lanark Scotland, do hereby declare
the nature of my invention for " IMPROVEMENTS IN THE MANUFACTURE
CHROMATES AND BICHROMATES," to be as follows:-
OF
This Invention has for its object improvements in the manufacture of chromates
and bichromates.
To manufacture chromate of lime I take chromate of soda by preference prepared
in the manner described in my application bearing even date with the present, and
after treating it as there described with chloride of calcium or chloride of barium
in order to eliminate the sulphate of soda &c. I heat the now almost pure solution
of chromate of soda with its equivalent quantity of caustic lime. The effect is to
precipitate chromate of lime and to leave caustic soda in solution, which becomes
available for the manufacture of chromate of soda. The chromate of lime pre-
cipitated, being washed by means of a hydro-extractor or filter press, is very pure
and can be used for almost all purposes to which chromate of potash is applied.
If desired the chromate of lime may be converted into bichromate of lime by
treating it with its equivalent of sulphuric acid to combine with half the lime, and
evaporating the liquor until sulphate of lime precipitates and bichromate of lime
remains in solution, when the latter is slowly evaporated to dryness and found to
be very soluble and pure.
In making bichromate of lime as before described the sulphate of soda etc may
not be eliminated from the chromate of lime from which the bichromate is to be
made as they with the additional sulphates made in converting the chromate into
bichromate of lime, may be eliminated together after the formation of bichromate
of lime.
Dated this 10th do 7001
CARPMAEL & Co.,
"Agents for the Applicant.

page_text: I WILLIAM JOHN ALEXANDER DONALD of number two Belgrave Terrace
Hillhead Glasgow Secretary and Commercial Manager of The Eglinton Chemical
Company Limited Glasgow in the County of Lanark Scotland do hereby declare
the nature of my invention for "IMPROVEMENTS IN THE MANUFACTURE OF
CHROMATES AND BICHROMATES" and in what manner the same is to be performed
to be particularly described and ascertained in and by the following statement :-
This Invention has for its object improvements in the manufacture of chromates
and bichromates.
To manufacture chromate of lime I take chromate of soda by preference prepared
in the manner described in my application No 4811 bearing even date with the
present and after treating it as there described with chloride of calcium or chloride
of barium in order to eliminate the sulphate of soda & I treat the now almost pure
solution of chromate of soda_with_its_equivalent quantity of caustic lime. The
effect is to precipitate chromate of lime and to leave caustic soda in solution which
becomes available for the manufacture of chromate of soda. The chromate of lime
precipitated being washed by means of a hydro-extractor or filter press is very
pure and can be used for almost all purposes to which chromate of potash is
applied.
If desired the chromate of lime may be converted into bichromate of lime by
treating it with its equivalent of sulphuric acid to combine with half the lime and
evaporating the liquor until sulphate of lime precipitates and bichromate of lime
remains in solution when the latter is slowly evaporated to dryness and found to be
very soluble and pure.
In making bichromate of lime as before described the sulphate of soda & may
not be eliminated from the chromate of lime from which the bichromate is to be
made as they with the additional sulphates made in converting the chromate into
bichromate of lime may be eliminated together after the formation of bichromate
of lime.
As is described in my Specification No 4811 this is done by the addition of
chloride of calcium or other soluble chloride having a reaction on sulphate of soda
to produce a more or less insoluble sulphate in the quantity required to combine
with the contained sulphate of soda.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that what
I claim is
1. The improvement heroin described in the manufacture of chromates consisting
in producing chromate of lime by the addition of caustic lime to chromate of soda
and in using the soda thus set free in the manufacture of chromate of soda as
herein described.
2. The improvement herein described in the manufacture of bichromate of lime
consisting in treating a mixed solution of chromate of lime and sulphate of soda

page_text: first with acid to convert the chromate into bichromate and then with a soluble
chloride having a reaction on the sulphate of soda to produce chloride of sodium
and a more or less insoluble sulphate substantially as described.
3. The processes for the manufacture of chromate and bichromate of lime sub-
stantially as described.
Dated the eth D
1001