IMPROVED MANUFACTURE OF BICHROMATE OF SODA
Year: 1882

page_text: LETTERS PATENT to Charles Denton Abel of N° 28 Southampton Buildings,
Chancery Lane, in the County of Middlesex for an Invention of "AN
" Communicated to him
IMPROVED MANUFACTURE OF BICHROMATE OF SODA
from abroad by Friedrich Carl Glaser of Berlin in the German Empire.
PROVISIONAL SPECIFICATION left by the said. Charles Denton Abel at the
Office of the Commissioners of Patents on the 15th December 1882.
CHARLES DENTON ABEL of No 28 Southampton Buildings, Chancery Lane in
the County of Middlesex "AN IMPROVED MANUFACTURE OF BICHROMATE OF
SODA "
[Communicated to him from abroad by Friedrich Carl Glaser of Berlin in
the German Empire.]
The bichromate of soda as at present manufactured has always contained water
in its composition, according to the formula: Na, Cr, O, + 2 H, O. This product
possesses the property of being strongly hygroscopic, forming in warm weather a
liquid or deliquescent mass, and being with difficulty retained in a crystalline form,
from which causes it is not suited for technical purposes.
The object therefore for which bichromate of soda was produced, namely to serve
as a substitute for the expensive bichromate of potash, could not be attained by the
above named product.
The present invention has for its object the production of commercially useful
bichromate of soda, which is attained by producing it in a perfectly anhydrous
form, in which it does not possess the above named objectionable qualities, and is
particularly suitable as a substitute for bichromate of potash.
The preparation of this product commences in the well known manner by
calcining lime or magnesia and carbonate of soda, or other carbonates or nitrates of
soda with the pulverised chromium ore. The soluble chromium compounds produced
are dissolved in water, and the lime or magnesia contained in the solution is pre-
cipitated by means of carbonate or bicarbonate of soda. In this stage of the process,
instead of, as heretofore, simply separating the product in crystalline form after the
addition of the acid, the liquors containing the chromate of soda are brought by

page_text: concentration over an open fire to about 40° to 45° Beaumé and combined hot
with sulphuric or hydrochloric acid, according to the formula:
2 (Na, Cr O₁) + H, SO₁ = Na, Cг, O + Na, SO, + H¸ O
After adding the acid, the substance is allowed to get cold whereby the sulphate
of soda, which is insoluble in the bichromate of soda solution is precipitated
quantitatively, so that an almost pure solution of bichromate of soda is produced..
This is evaporated to dryness in cast iron vessels and the heating is continued after
dryness has been reached,, whereby the whole mass is melted down to a deep
blackish brown liquid, which is cast in suitable moulds and is ready for the market
as almost pure bichromate of soda.
Whereas the aqueous bichromate of soda is a body having physical properties
which render it of difficult application for technical purposes, the product resulting
from the above described process is free from such properties, inasmuch as by its
compact form it offers comparatively little surface for the absorption of water, and
is therefore only slightly hygroscopic.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Charles Denton Abel in the Great Seal Patent Office on the
1st June 1883.
CHARLES DENTON ABEL of N° 28 Southampton Buildings Chancery Lane in
the County of Middlesex "AN IMPROVED MANUFACTURE OF BICHROMATE OF
SODA A communication to me from Abroad by Friedrich Carl Glaser of Berlin in
the German Empire.
"
The bichromate of soda as at present manufactured has always contained water
in its composition, according to the formula: Na, Cr, O, + 2H, O. This product
possesses the property of being strongly hygroscopic, forming in warm weather a
liquid or deliquescent mass, and being with difficulty retained in a crystalline
form; from which causes it is not suited for technical purposes..
The object therefore for which bichromate of soda was produced, namely to serve
as a substitute for the expensive bichromate of potash, could not be attained by the
above named product.
The present invention has for its object the production of commercially useful
bichromate of soda, which is attained by producing it in a perfectly anhydrous
form, in which it does not possess the above named objectionable qualities, and is
particularly suitable as a substitute for bichromate of potash..
The preparation of this product commences in the well known manner by
calcining lime or magnesia and carbonate of soda, or other carbonates or nitrates of
soda with the pulverised chromium ore. The soluble-chromium compounds
produced are dissolved in water, and the lime or magnesia contained in the solution
is precipitated by means of carbonate or bicarbonate of soda. In this stage of the

page_text: process, instead of, as heretofore, simply separating the product in crystalline form
after the addition of the acid, the liquors containing the chromate of soda are
brought by concentration over an open fire to about 40° to 45° Beaumé and
combined hot with sulphuric or hydrochloric acid, according to the formula:
2 (Na, Cr O₁) + H, SO₁ = Na, Cr, O, + Na, SO, +.H₂ O.
After adding the acid, the substance is allowed to get cold whereby the sulphate
of soda, which is insoluble in the bichromate of soda solution, is precipitated
quantitatively, so that an almost pure solution of bichromate of soda is produced.
This is evaporated to dryness in cast iron vessels and the heating is continued after
dryness has been reached, whereby the whole mass is melted down to a deep
blackish brown liquid, which is cast in suitable moulds and is ready for the market
as almost pure bichromate of soda.
Whereas the aqueous bichromate of soda is a body having physical properties
which render it of difficult application for technical purposes, the product resulting
from the above described process is free from such properties, inasmuch as by its
compact form it offers comparatively little surface for the absorption of water, and
is therefore only slightly hygroscopic.
Having thus described the nature of this invention and in what manner the
same is to be performed as communicated to me by my foreign correspondent, I
claim
The herein described manufacture of anhydrous bichromate of soda by heating
the bichromate, after its separation by means of acid, to such a degree that it
becomes melted, the solidified product being then brought into commerce.
In Witness whereof I the said Charles Denton Abel have hereunto set my
hand and seal this first day of June in the year of our Lord One thousand*
eight hundred and eighty-three.
CHA³. D. ABEL (L.S.).