IMPROVEMENTS IN THE MANU- · FACTURE OF CHROMATES
Year: 1877

page_text: LETTERS PATENT to Hugh McCulloch Drummond, of Irvine, in the County of
Ayr, and William John Alexander Donald, of Glasgow, in the County of
Lanark, North Britain, for the Invention of "IMPROVEMENTS IN THE MANU-
· FACTURE OF CHROMATES."
Sealed the 29th December 1877, and dated the 5th July 1877.
PROVISIONAL SPECIFICATION left by the said Hugh McCulloch Drummond
and William John Alexander Donald at the Office of the Commissioners of
Patents on the 5th July 1877.
HUGH McCULLOCH DRUMMOND, of Irvine, in the County of Ayr, and WILLIAM
JOHN ALEXANDER DONALD, of Glasgow, in the County of Lanark, North Britain.
"IMPROVEMENTS IN THE MANUFACTURE OF CHROMATES."
This Invention has for its object the manufacturing of chromates in a more
economical and satisfactory manner than heretofore, and it consists in furnacing the
chrome ore with limestone or carbonate of lime, and with sulphate of potash or of
soda, to which an excess of sulphuric acid has been added.
.
In carrying out the Invention the furnace and other apparatus employed may be
the same as that heretofore in use in making chromates. The chrome ore is finely
pulverised, and the limestone or carbonate of lime is in a crushed or roughly pul-
verised condition. The sulphate of potash or of soda may be made in the ordinary
way by treating chloride of potassium or of sodium with sulphuric acid, and the
excess of acid having been added, the compound after cooling is ground and inti-
mately mixed with the chrome ore and carbonate of lime."
The proportions of the materials employed may be for every 100 parts by weight
of chrome ore about 240 parts of carbonate of lime, about 125 parts of sulphate of
potash, or 100 parts of sulphate of soda, and about 40 parts of sulphuric acid.
Chromates obtained by the improved process herein-before described may be
converted into bichromates of the same bases, or into chromates or bichromates of
other bases in the ordinary way.

page_text: SPECIFICATION in pursuance of. the conditions of the Letters Patent filed by
the said Hugh McCulloch Drummond and William John Alexander Donald in
the Great Seal Patent Office on the 4th January 1878.
HUGH MCCULLOCH DRUMMOND, of Irvine, in the County of Ayr, and WILLIAM
JOHN ALEXANDER DONALD, of Glasgow, in the County of Lanark, North Britain.
"IMPROVEMENTS IN THE MANUFACTURE OF CHROMATES."
Our said Invention has for its object the manufacturing of chromates in a more
economical and satisfactory manner than heretofore, and it consists in furnacing the
chrome ore with limestone or carbonate of lime, and sulphate of potash or of soda,
to which an excess of sulphuric acid has been added.
In carrying out our said Invention the furnace and other apparatus employed may
be the same as that heretofore in use in making chroinates. The chrome ore is finely
pulverised, and the limestone or carbonate of lime is in a crushed or roughly pul-
verised condition. The sulphate of potash or of soda may be made in the ordinary
way by treating chloride of potassium or of sodium with sulphuric acid, the excess
of acid being added at the same time or subsequently. The compound of sulphate
and bisulphate after cooling is ground and intimately mixed with the chrome ore
and carbonate of lime. The mixed materials are subjected in the furnace to a
similar heat and for the same length of time as those adopted in the ordinary
process. We however prefer that at the first stage of the furnacing process the heat
should be comparatively low, and that towards the end of the six or eight hours
furnacing it should be raised to the usual maximum temperature.
The proportions of the materials employed which we would recommend are, for
every 100 parts by weight of chrome ore (assumed to be of an average strength of
44 per centum), 240 to 250 parts of limestone or carbonate of lime, 125-parts of
sulphate of potash or 100 parts of sulphate of soda, and 40 parts sulphuric acid.
These proportions are subject to variation in different cases, and that of the excess
of sulphuric acid may vary between 10 parts per centum and the proportion required
to convert the potash or soda into bisulphate.
The operations subsequent to the furnacing may be conducted in the same way
´as heretofore, and the chromates obtained may be converted into bichromates of
the same bases, or into chromates or bichromates of other bases in the ordinary
way.
Having thus particularly described our said Invention and the manner of per-
forming the same, we have to state that what we believe to be novel and original,
and claim as the Invention secured to us by the herein-before in part recited
'Letters Patent is, the obtaining of chromates by furnacing chrome ore with lime-
stone or carbonate of lime, and with sulphate of potash or of soda, to which an
excess of sulphuric acid has been added, as herein-before described.
In witness whereof, we, the said Hugh McCulloch Drummond and William
John Alexander Donald, have hereunto set our hands and seals, this Third
day of January, in the year of our Lord One thousand eight hundred and
seventy-eight
H. M. DRUMMOND.
(L.S.)
WILLIAM J. A. DONALD.
(L.S.)