tion of Sulphides and other Impurities, and in the Recovery and Reuse of the Reagents Employed therein.
Year: 1885

page_text: tion of Sulphides and other Impurities, and in the Recovery
and Reuse of the Reagents Employed therein.
I THOMAS DAVID OWEN of 9 Falkland Road Egremont in the County of
Chester Analytical Chemist do hereby declare the nature of the said invention
for "IMPROVEMENTS IN THE TREATMENT OF VAT LIQUOR FOR THE ELIMINATION
OF SULPHIDES AND OTHER IMPURITIES AND IN THE RECOVERY AND RE-USE OF
THE RE AGENTS EMPLOYED THEREIN to be as follows:-
"
The objects are to treat vat liquor so as to allow of marketable carbonate and
Caustic soda being obtained direct from impure solutions of the same, and to recover
and re use the reagents employed therein.
In carrying out my invention I proceed as follows:-I take vat liquor coming
from the lixiviation of Black Ash preferably of 1.300 specific gravity or thereabouts
and allow it to settle in tanks I then decant the settled liquor into suitable vessels
where the solution is heated (preferably by a dry steam coil) to nearly boiling
point I then add oxide of Lead thereto in sufficient quantity to decompose the
whole of the sulphides of sodium contained in the solution. I find in practice that
the re action is very rapid, and that the sulphides of Lead formed settle rapidly,
and carry down with them practically the whole of the iron held in solution.
The purified solution of Carbonate and Caustic Soda, obtained as above setforth
is run into suitable crystallizing vessels, and when the greater part of the Carbonate
of soda has become crystallized, the remaining liquor consists of a solution of
caustics together with a small quantity of Carbonate of Soda, which carbonate
of soda practically may be to a large extent separated by concentrating and re
crystallizing or by other suitable methods. The solution mainly of Caustic Soda
is ultimately evaporated and made into solid Caustic Soda.
The crystals of Carbonate of Soda obtained as herein setforth will be found to
contain not more than 0.2 or 0.4 per cent of Caustic Soda.
The sulphide of Lead formed in the purification of vat liquor as hereinbefore
setforth is roasted at a low red heat, preferably without or with only partial
previous washing, so as to facilitate the conversion of the sulphide of Lead into oxide.
After roasting the oxide of Lead is washed with water to free it from alkaline

page_text: salts, and is then in a suitable condition for reuse. I prefer to make up any loss
of Lead in process by the use of sulphate of Lead obtained as a bye product from
vitriol chambers previously freed from arsenic by suitable means.
When contaminated with iron and other impurities by frequent re use we treat
the Lead compounds with strong sulphuric or Hydrochloric acid, so as to dissolve
out and free the Lead from the said impurities. The resulting sulphate or chloride
of Lead may be converted into Carbonate or oxide of Lead by roasting or boiling
with alkali before being re used for purifying vat liquors.
Dated this seventh day of January 1885.

page_text: and Reuse of the Reagents Employed therein.
I THOMAS DAVID OWEN of 9 Falkland Road Egremont Cheshire, Analytical
Chemist, do hereby declare the nature of the said invention for "IMPROVEMENTS
IN THE TREATMENT OF VAT LIQUOR FOR THE ELIMINATION OF SULPHIDES AND
OTHER IMPURITIES, AND IN THE RECOVERY AND REUSE OF THE REAGENTS EMPLOYED
THEREIN and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:—
,,
The objects are to treat vat liquor so as to allow of marketable carbonate and
caustic soda being obtained direct from impure solutions of the same, and to recover
and reuse the reagents employed therein.
In carrying out my invention I proceed as follows:-I take vat liquor coming
from the lixiviation of black ash preferably of 13 specific gravity or thereabouts
and allow it to settle in tanks. I then decant the settled liquor into suitable
vessels where the solution is heated (preferably by a dry steam coil) to nearly boiling
point. I then add oxide of lead, or oxide of lead dissolved in an alkaline solution
thereto in sufficient quantity to decompose the whole of the sulphides of sodium
contained in the solution.
I find in practice that the reaction is very rapid, and that the sulphides of lead
formed settle rapidly and carries down with them practically the whole of the iron
held in solution.
The purified solution of carbonate and caustic soda obtained as above setforth is
run into suitable crystallizing vessels, and when the greater part of the carbonate
of soda has become crystallized the remaining liquor consists of a solution of
caustic together with a small quantity of carbonate of soda, which carbonate
of soda practically may be to a large extent separated by concentrating and
recrystallizing or by other suitable methods. The solution mainly of caustic
soda is ultimately evaporated and made into solid caustic soda.
The crystals of carbonate of soda obtained as herein setforth will be found to
contain not more than 0.2 or 0.4 per cent of caustic soda.
The sulphide of lead formed in the purification of vat liquor as hereinbefore
setforth is roasted at a low red heat preferably without or with only partial
previous washing so as to facilitate the conversion of the sulphide of lead into
oxide. After roasting the oxide of lead is washed with water to free it from
alkaline salts and is then in a suitable condition for re use. I prefer to make
up any loss of lead in the process by the use of sulphate of lead obtained as a bye
product from vitriol chambers, and previously freed from arsenic by any suitable
means.
When contaminated with iron and other impurities by frequent re use I treat
the lead compounds with strong sulphuric or hydrochloric acid so as to dissolve
out, and free the lead from, the said impurities. The resulting sulphate or chloride

page_text: of lead may be converted into carbonate or oxide of lead by roasting or boiling
with alkali, before being re used for purifying vat liquors.
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
First. Purifying vat liquor for the joint formation of crystal soda and strong
caustic liquor by the agency of lead oxide and heat substantially as setfortb..
Second. Recovering sulphide of lead in the form of oxide of lead for reuse in the
purification of vat liquor substantially as setforth.
Third. Using purified sulphate of lead obtained from vitriol chambers, in the
purification of vat liquors substantially as setforth.
Fourth. Treating the compounds of lead used in the purification of vat liquors
with acid substantially in the manner and for the purpose setforth.
Dated this fifth day of October 1885.
J. T. KING,
Per J. Johnson,
Agent.