IMPROVEMENTS IN THE MANUFACTURE OF SALTS OF CHROMIUM FROM CHROME ORE
Year: 1864

page_text: PROVISIONAL SPECIFICATION left by John Knowles Leather at the
Office of the Commissioners of Patents, with his Petition, on the
6th September 1864.-A communication from abroad. by Benedict
- Margulies, of Trieste, in the Empire of Austria.
I, JOHN KNOWLES LEATHER, of Saint Helen's, in the County of Laricaster,
Manufacturing Chemist, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN THE MANUFACTURE OF SALTS OF CHROMIUM FROM CHROME
ORE," to be as follows:-
I take a mixture of lime, or of hydrate of lime, or of other alkaline earths,
and of one or more of the salts of potash or soda, and of chrome ore reduced
to a finely divided state, with or without feldspar, and with or without
manganese or other oxygen-bearing material, and form it into blocks by
pressing it together, either in a dry state or after the addition of water.
These blocks may be of any size or shape, but I prefer to make them in the
shape of a cone, eighteen inches high, eight inches wide at the top, and nine
inches wide at the base. I also prefer to use a mixture of hydrate of lime
and sulphate of potash, or sulphate of soda and chrome ore, and after well
mixing it in any convenient manner to add water, and knead it till it possesses
the consistency of clay, when I press it into moulds of a conical shape. I
expose the blocks of whatever size or shape they may be, either dry or in a
moist state, to the heat of a furnace till the chrome ore is either wholly
partially decomposed. I then take the blocks and place them in any con-
venient vessel, and dissolve out the salts of chromium, and treat the solution
by any of the usual methods for the manufacture of chrome salts.

page_text: Hitherto it has been usual to manufacture salts of chromium by taking a
mixture of chrome ore in a finely divided state, and of lime or hydrate of
lime, or other alkaline earths or feldspar, with or without one or more of the
salts of potash or soda, and with or without manganese or other oxygen-
bearing material, and spreading the same on the bed of a reverberatory
furnace, so as to exposo as largo a surface as possible to the action of the
heat and oxidising influences of the heated gases contained within the furnace,
and by frequent stirring of the mixture to expose fresh surfaces to the action
of the heated air until the chrome ore has been either wholly or partially
decomposed.
Now my process is precisely opposite. I have not found it possible in
ordinary practice to produce an oxidizing flame perfectly pure, because the
heated air within the furnace is always more or less mixed with carbon or
other reducing gases, and consequently that part of the mixture which may
have been advanced in the process of oxidation is liable to bo robbed of its
oxygen, and again reduced into an insoluble state by any unconsumed carbon
or other reducing gasos which may be floating in the furnace. Thereforo I
form the mixture into a compact mass, so as to expose as little surface to tho
flame as possible consistent with the proper heating of the block, and leave it
to the particles contained in the mass to decompose each other by contact
under the influence of heat. In preparing my mixture I prefer to uso equal
parts by weight of all materials specified, but other quantities may also
be used.