IMPROVEMENTS IN THE MANUFACTURE OF PHOSPHATIC SALTS
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 PHOSPHATIC SALTS to be as follows:-
My invention consists in a process for utilizing the Phosphorus contained in
pig-iron.
By my process when molten phosphoric iron is treated in Basic-lined converters
or furnaces I add Magnesia or Magnesia and oxide of iron or manganese to the iron
which I prefer to have been decarburised by a previous operation. Phosphate of
Magnesia is thus produced by the action of the Phosphorus and Oxygen on the
Magnesia and forms a slag with some oxide of iron. This is run off and either
fused or boiled with carbonate or hydrate of soda or potash or otherwise treated.
Both the phosphoric acid and magnesia may be thus recovered.
Doted this Fighth day of March 1884
SIDNEY GILCHRIST THOMAS.

page_text: 1, 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 PHOSPHATIC SALTS and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
By my invention I take molten phosphoric pig iron-the higher the content in
phosphorus the better-or preferably molten phosphoric iron which has been first
desiliconised in a silica lined vessel-and treat it in a converter or regenerative gas
furnace with a basic or neutral lining, with magnesia, using only about 4 to 5 times
the weight of magnesia that there is of phosphorus in the iron. The magnesia is
thrown into the vessel or furnace before introducing the molten iron. In the open
hearth furnace process the magnesia may be mixed with oxide of iron. The
operation is then conducted as is usual in the Basic or Thomas-Gilchrist Bessemer
or Siemens operations till a test shows the iron to be practically free from
phosphorus when the metal and slag are poured off separately. I find in this way
a slag is produced far less.in weight than the ordinary Basic slag and containing
less iron, while it contains all the phosphorus originally in the pig iron, in the
easily recoverable form of phosphate of Magnesia. This slag I then boil or
preferably fuse with caustic, or carbonate of soda or potash, and thus obtain the
phosphate in a soluble form and the magnesia in a shape in which it may be used
over again to take up a fresh quantity of phosphorus.
Instead of this last mode of treatment the magnesian phosphatic slag may be
dissolved in dilute hydrochloric acid and after precipitation of the phosphoric acid
with lime, the solution of magnesian chloride is heated till it is decomposed into
magnesia and hydrochloric acid, this decomposition being a well known reaction.
It is to be observed that the use of magnesia presents the following important
advantages as a means for recovering in a utilisable form of phosphate the
phosphorus contained in phosphoric pig iron 1. It has a low combining weight
which results in saving material, heat and cost of handling.
2. It is not volatile at high temperatures.
3. It. is. readily recoverable from the phosphoric acid combinations by the
methods herein described by which also merchantable phosphates are simultaneously
produced.
Having now particularly described and ascertained the naturo of my said
Invention and in what manner the same is to be performed I declare that what
I claim is
1 The employment of magnesia in treating molten phosphoric iron in Basic or
neutral lined converters or furnaces as a means of producing merchantable phosphatic
salts from the phosphorus contained in such iron.
2. In the production of phosphatic salts from phosphoric pig iron the continuous
regeneration of the magnesia employed substantially as herein described.
Dated this 12th day of December 1884.