A Method of Treating Waste or Spent Sulphuric Acid Pickle Produced. in the Manufacture of Tin, Terne, and Black Plate..
Year: 1889

page_text: Date of Application, 18th Mar., 1889
Complete Specification Left, 14th Dec., 1889-Accepted, 8th Feb., 1890
PROVISIONAL SPECIFICATION.
A Method of Treating Waste or Spent Sulphuric Acid Pickle Produced.
in the Manufacture of Tin, Terne, and Black Plate..
I, SAMUEL DAW, of 2 West End, Llanelly, in the County of Carmarthen, Assayer,.
do hereby declare the nature of my invention to be as follows:-
:-
In many works where tin, terne and black plate are manufactured it is.
necessary at certain stages of the manufacture to immerse the iron or steel plates in
dilute sulphuric acid for the purpose of removing scale and causing the plates to
present a uniform metallic surface which is necessary for the subsequent process of
coating the plates with tin or terne as the case may be.
This invention consists in treating the residual liquor from this process, known as
waste or spent pickle in the following manner, to produce useful products.
To the waste or spent sulphuric acid pickle (subjected or not subjected to any
preparatory treatment) for instance, taking a quantity of 1000 gallons, I add for every
32 pounds weight of Sulphur found in combination with the constituents of the waste
or spent sulphuric acid pickle such quantity of any suitable material as may contain
about 40 pounds weight of available oxide of magnesium so that the addition of the
material containing oxide of magnesium may cause by chemical action the production
of oxide of iron and sulphate of magnesia. These two substances may be separated by
any suitable method.
Dated this 18th day of March 1889
COMPLETE SPECIFICATION.
A Method of Treating Waste or Spent Sulphuric Acid Pickle Produced
in the Manufacture of Tin, Terne, and Black Plate.
•
1 SAMUEL DAW, of 2 West End Llanelly, in the County of Carmarthen, Assayer,
do hereby declare the nature of my invention and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:-
In many works where tin, terne, and black plate are manufactured it is necessary at
certain stages of the manufacture to immerse the iron or steel plates in dilute sulphuric
acid for the purpose of removing scale and causing the plates to present a uniform
metallic surface which is necessary for the subsequent process of coating the plates
with tin or terne as the case may be.
This invention consists in treating the residual liquor from the process, known as
waste or spent pickle in the following manner, to produce useful products.
To the waste or spent sulphuric acid pickle subjected or not subjected to any
preparatory treatment for instance taking a quantity of 1000 gallons, I add for every
32 pounds weight of sulphur found in combination with the constituents of the waste
or spent sulphuric acid pickle such quantity of any suitable material as may contain
about 40 pounds weight of available oxide of magnesium so that the addition of the
material containing oxide of magnesium may cause by chemical action the production
of oxide of iron and sulphate of magnesium.
These two substances may be separated by any suitable method.
This invention may be performed as follows
The strength of the waste sulphuric acid pickle is determined by estimating the
quantity of combined sulphur present in a sample drawn from the bulk.

page_text: One hundred gallons of waste pickle are transferred to an ordinary round iron
evaporating pan 4 feet diameter at the top and about 2' 6" at its greatest depth.
The evaporating pan is supported over a fire.
The strength of the waste pickle being known a quantity of material containing
available oxide of magnesium is added in sufficient, quantity to cause the sulphuric
acid and solution of sulphate of iron to be changed by chemical action into sulphate of
magnesia which remains in solution and a hydrated oxide of iron which is precipitated.
If calcined magnesite be used 40 to 50 parts by weight must be added for every
32 parts by weight of combined sulphur found in the waste pickle.
If calcined dolomite be used an allowance must be made for the calcium oxide
present in calcined dolomite about 40 to 50 parts by weight of calcined dolomite must
be added for every 32 parts by weight of combined sulphur found in the waste pickle.
The contents of the evaporating pan are caused to boil by a fire placed under the
evaporating pan causing most of the water to evaporate leaving a semi solid residue
at the bottom of the pan. This residue is calcined at a full red heat in any ordinary
calcination furnace. After about 5 to 6 hours calcination the charge is withdrawn
from the furnace and digested with hot water in a vat 4 feet diameter by 4 feet deep,
for 1 hour when most of the sulphate of magnesia will be disolved out leaving the
ferric oxide as a powder at the bottom of the vat.
The whole is allowed to stand until the ferric oxide has subsided and the supernatant
liquor becomes clear.
The clear solution of sulphate of magnesia is run off in shallow wooden coolers
12 feet by 12 feet by 9 inches deep.
. After some time crystals of sulphate of magnesia fall and may be collected from
the mother liquor and slightly dried.
The ferric oxide is collected ground and dried.
Having now particularly described and ascertained the nature of my said
invention and in what mauner the same is to be performed I declare that what
I claim is
The method of treating the material usually known as spent sulphuric acid pickle
with or without preliminary treatment consisting in adding thereto material containing
available oxide of magnesium so that sulphate of magnesia and oxide of iron are
produced.
DCOGITEC
HERBERT & Co.,
18, Buckingham Street, Strand, London, W.C., Agents to Applicant.