IMPROVEMENTS IN THE MANUFACTURE OF CHROMIC COMPOUNDS
Year: 1884

page_text: I, SIDNEY GILCHRIST THOMAS of 9 Palace Chambers, Westminster Bridge,
London, temporarily residing at El Biar in the French Colony of Algeria,
Metallurgist do hereby declare the nature of my invention for IMPROVEMENTS IN
THE MANUFACTURE OF CHROMIC COMPOUNDS to be as follows:-
My invention relates to the manufacture of chromic compounds from chrome
iron ore By my invention I first treat the chromic iron-ore in a blast furnace
preferably using an excess of coke or charcoal and very hot blast so as to produce
a pig containing nearly all the chrome alloyed with iron and carbon. This chrome
pig is then treated in a fluid state in a gas furnace or Bessemer Converter which
must be provided with a basic lining such as of lime, magnesia or of chrome iron
Into this converter or furnace there is introduced a quantity of lime or
of alkaline chloride, sulphate or carbonate more than sufficient to combine with the
chromic acid formed by the oxidation of the chrome, as well as with any silicon or
phosphorus present in the pig. A slag consisting largely of alkaline or calcic
chromate is formed and being run off is lixiviated with water and the solution
treated for the manufacture of any chrome salt required.
ore.
:

page_text: I SIDNEY GILCHRIST THOMAS of 9 Palace Chambers Westminster Bridge London
temporarily residing at El Biar in the French Colony of Algeria Metallurgist do
hereby declare the nature of my Invention for IMPROVEMENTS IN THE MANUFACTURE
OF CHROMIC COMPOUNDS and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement:-
My invention relates to the manufacture of chromic compounds from chrome
iron ore.
By my invention I first treat the chromic iron ore in a blast furnace,
preferably using an excess of coke or charcoal and very hot blast, so as to produce
a pig containing nearly all the chrome alloyed with iron and carbon. This chrome
pig is then treated in a molten state in a gas furnace or Bessemer converter which
must be provided with a Basic or neutral lining such as of lime, magnesia, or of
chrome iron ore. Into this converter or furnace there is introduced a quantity of
lime or of alkaline chloride or of alkaline carbonate or hydrate or of magnesia,
more than sufficient to combine with the chromic oxide formed by the oxidation of
the chromium as well as with any silicon or phosphorus present in the crude iron.
I greatly prefer to use potassic or sodio carbonate or hydrate.
The operation is then conducted as in the manufacture of steel till the whole of
the chromium is oxidised and transformed into chromate; to facilitate this oxida-
tion the quantity of blast introduced should be much larger than is employed
in the ordinary Bessemer operation, and a special blast twyer is introduced if a
Siemens furnace is employed.
A slag consisting largely of alkaline or calcic chromate with some silicote is
formed, and being run off is lixiviated with water and the solution treated for the
manufacture of any chrome salt required.
By this process chrome iron ore much poorer in chrome oxide than is ordinarily
employed can be very economically utilised, the iron also being simultaneously
recovered as ingot metal.
I would observe that I do not claim the use of Basic or neutral linings for
converters or furnaces.
t
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:-
The improvements in the manufacture of chromic compounds consisting in
treating the chrome ore in a blast furnace for the production of crude chrome
pig iron and then treating the molten pig in a Basic or neutral lined converter or
furnace with alkalies or lime so as to obtain directly alkaline or lime chromates
substantially as herein described.
Dated this 75th day of Decembar 1884