Improvements in Utilizing the Residual Products obtained in the Working of certain kinds of Voltaic Batteries.
Year: 1896

page_text: Improvements in Utilizing the Residual Products obtained in the
Working of certain kinds of Voltaic Batteries.
We WILLIAM WALKER the younger of No. 36 Gillott Road Birmingham in the
County of Warwick, Electrician and FRANK RICHARD WILKINS of Spring Hill Wharf
Birmingham aforesaid Gentleman and JABEZ LONES of South Road, Smethwick in
the County of Stafford Ironmaster and JOSEPH LONES, of No. 93 Regent Street
Smethwick aforesaid Analytical, Metallurgical and Consulting Chemist do hereby
declare the nature of this invention to be as follows:-
In the working of voltaic batteries in which the exciting liquid is a solution of
caustic potash or caustic soda, the spent or exhausted exciting liquid consists of a
solution of caustic potash or caustic soda saturated or nearly saturated with oxide of
zinc. The object of the said invention is the economical recovery of the dissolved
zine and the revivifying of the solution of potash or soda, that is the restoration of
its causticity; by which revivifying the said solution is fitted to be again employed
as the exciting liquid of a voltaic battery.
We will describe the said invention in connection with a spent solution of caustic
potash.
In carrying the said invention into effect we proceed as follows.
spent solution, that is, the solution of potash saturated with oxide of zinc in either of
the following ways. According to one of the processes We employ; We heat the
spent solution to boiling and slowly add flowers of sulphur to the boiling solution so
long as a precipitate is formed in the boiling liquid. The precipitate formed is
sulphide of zinc. The said sulphide of zinc is separated from the liquid by filtration,
or by subsidence and decantation. The said sulphide is washed and dried and may
be treated in the way hereinafter described or used for any purpose to which sulphide
of zinc is or may be applicable. By this process the whole of the zinc is recovered
but the solution of potash is not restored to its original state as by the reaction of
the sulphur with which the solution has been boiled thiosulphate of potash is produced
which unfits the solution for re-use in a voltaic battery. The said thiosulphate may
be removed by oxidizing it into sulphuric acid by means of either per-oxide of
hydrogen or per-oxide of barium or by electrolysis and the sulphuric acid produced
may be removed by treating the solution first with quicklime and afterwards with
caustic baryta.
According to another of the processes we employ we prepare sulphide of potassium
by heating two parts by weight of caustic potash or carbonate of potash with one
part by weight of flowers of sulphur until the whole is thoroughly melted. The
resulting inass consists of a mixture of sulphide of potassium and thiosulphate of
potash. The cooled and powdered mass is digested with rectified spirit of wine by
which the sulphide of potassium is dissolved, the thiosulphate of potash being left

page_text: undissolved. By decantation the alcoholic solution of sulphide of potassium is
separated from the thiosulphate of potash. The alcoholic solution of sulphide of
potassium is heated in a distillatory apparatus by which the alcohol is recovered.
The pure sulphide of potassium thus obtained is dissolved in a small quantity of
water and the solution is slowly added to the boiling spent liquid until the whole of
the zinc contained in it is precipitated. The filtrate is boiled with a little quicklime
or caustic baryta to decompose any carbonate of potash which may have been formed.
The clear liquor is evaporated until it has acquired its original strength when it is
ready to be used again as the exciting liquid of a voltaic battery. Or we make the
sulphide of potassium with which we precipitate the zinc as sulphide of zinc by
heating a mixture of sulphate of potash and carbon.
According to another process we pass sulphuretted hydrogen gas through the spent
solution as long as a precipitate is formed. The solution from which the precipitated
sulphide of zinc has been separated is boiled with caustic lime or caustic baryta as
herein before described. The sulphuretted hydrogen gas may be generated by the
action of dilute sulphuric acid on sulphide of iron.
The sulphide of zinc obtained by the methods described may be reduced to
inetallic zinc by the well known inethods. Or the sulphide of zinc mixed with a little
flowers of sulphur may be heated to a low red heat for a short time whereby it is
partially desulphurised and acquires a whiteness and density which fit it to be used
as a white pigment.
Dated this first day of September 1896
Improvements in Utilizing the Residual Products obtained in the
Working of certain kinds of Voltaic Batteries.
We, WILLIAN WALKER, the younger of No 36 Gillott Road, Birmingham, in the
County of Warwick, Electrician, and FRANK RICHARD WILKINS, of Spring Hill Wharf,
Birmingham, aforesaid, Gentleman, and JABEZ LONES, of South Road, Smethwick, in
the County of Stafford, Ironmaster, and JOSEPH LONES, of No. 93 Regent Street,
Smethwick, aforesaid, Analytical, Metallurgical and Consulting Chemist, do hereby
declare the nature of the said invention and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement :-
In the working of voltaic batteries in which the exciting liquid is a solution of
caustic potash or caustic soda, the spent or exhausted exciting liquid consists of a
solution of caustic potash or caustic soda saturated or nearly saturated with oxide of
zine. The object of the said invention is the economical recovery of the dissolved
ziuc and the revivifying of the solution of potash or soda, that is, the restoration of its
causticity; by which revivifying the said solution is fitted to be again employed as
the exciting liquid of a voltaic battery.
We will describe the said invention in connection with a spent solution of caustic
potash.
In carrying the said invention into effect we proceed as follows. We treat the spent. 4
solution that is, the solution of potash charged with oxide of zino in either of the
following ways. According to one of the processes we employ we heat the spent

page_text: solution to boiling and slowly add flowers of sulphur to the boiling solution so long as
a precipitate is formed in the boiling liquid. The flowers of sulphur form with the
potash, sulphide of potassium, by which the zine in the solution is precipitated as
sulphide of zinc, nine ounces of flowers of sulphur to a gallon of spent solution having
a specific gravity of 1-22, being generally sufficient. The said sulphide of zine ia
separated from the liquid by filtration or by subsidence and decantation. The said
sulphide is washed, the first washings being added to the clear liquor, and afterwards
dried. The sulphide of zinc inay be treated in the way hereinafter described or
used for any purpose to which sulphide of zine is or may be applicable.
By the process described some thiosulphate of potash is formed which may be
removed in either of the following ways:-
First, by the use of peroxide of hydrogen. The treated spent solution is allowed to
cool and a strong solution of peroxide of hydrogen is slowly added, the solution being
constantly stirred, until it is found on testing that the whole of the thiosulphate has
been oxidised into sulphate. This may be ascertained on a small scale by taking a
small quantity of the liquid say, in a test tube, and ascertaining that it no longer
possesses the property of dissolving chloride of silver.
Secondly the thiosulphate of potash may be converted into sulphate of potash by
the use of peroxide of barium. The peroxide of barium is first mixed with water and the
mixture is slowly added to the treated spent solution the solution being constantly
stirred during the addition of the peroxide of barium. The solution is tested from
time to time in the way already described until it is found that the clear solution no
longer possesses the property of dissolving chloride of silver.
Thirdly the thiosulphate of potash may be converted into sulphate of potash by
electrolysis. The solution is kept in agitation and electrolysed as long as there is no
effervescence or escape of oxygen at the anode of the electrolytic arrangement. When
the escape of gas that is, oxygen occurs the whole of the thiosulphate of potash has
been oxidised into sulphate of potash.
The solution treated in either of the ways above described for the conversion of
any thiosulphate of potash into sulphate of potash is then diluted until a specific
gravity of 105 is obtained. It is then boiled and cream of lime that is, a mixture of
quicklime and water, added for the purpose of saturating the sulphuric acid and
cauterizing any carbonate of potash which may have been formed during the working
of the battery by absorption of carbonic acid from the air. The boiling is continued
for about thirty minutes and the solution is treated with a little baryta water to
remove any remaining sulphate. The clear liquid is then separated and evaporated
until it has acquired its original strength when it may be re-used in a voltaic
battery.
According to another of the processes we employ for precipitating the zinc from
the spent solution in the form of sulphide of zine, we prepare sulphide of potassium
by heating two parts by weight of caustic potash or carbonate of potash with one
part by weight of flowers of sulphur until the whole is thoroughly melted. The
resulting mass consists of a mixture of sulphide of potassium and thiosulphate of
potash. The cooled and powdered mass is digested with rectified spirit of wine one
pound weight of the mixture requiring about one quart of spirit of wine. By
agitation the sulphide of potassium is dissolved by the spirit of wine the thiosulphate
of potash being left undissolved. By decantation the alcoholic solution of sulphide of
potassium is separated from the thiosulphate of potash. The alcoholic solution of
sulphide of potassium is heated in a distillatory apparatus and the alcohol recovered.
The pure sulphide of potassium thus obtained is dissolved in a small quantity of water
and the solution is slowly added to the boiling spent liquid until the whole of the
zinc contained in it is precipitated. The filtrate from the precipitate is diluted until
a specific gravity of 1.05 is obtained when it is boiled with cream of lime or caustic
baryta for the purpose of decomposing any carbonate of potash which may have been
formed. The liquid is separated from the lime and carbonate of lime by filtration or
decantation and the clear liquid is evaporated until its original strength is obtained
when it is ready to be used again as the exciting liquid of a voltaic battery.

page_text: According to another process for precipitating the zinc from the spent solution in
the form of zinc sulphide we prepare sulphide of potassium by mixing two parts by
weight of potassium sulphate with one part by weight of finely divided charcoal or
coal. The mixture is heated in a crucible until gas ceases to be evolved. The
Inolten mass is run on to a metal plate and allowed to cool. The cooled mass is
digested with warm water so as to dissolve the sulphide of potassium the uncou-
sumed carbon being separated therefrom by filtration or decantation. The sulphide
of potassium thus obtained is employed for precipitating the zinc from the
spent or exhausted exciting liquid from voltaic batteries in the manner hereinbefore
described.
According to another process for precipitating the zinc from the spent solution
sulphuretted hydrogen gas is passed through the warmed spent solution as long as a
precipitate is formed. The sulphuretted hydrogen gas may be generated by the
action of dilute sulphuric acid ou sulphide of iron. The precipitate, sulphide of zinc,
is separated from the liquid by filtration or decantation and thoroughly washed the
washings being added to the liquid. The liquid is treated with caustic lime or
caustic baryta as hereinbefore described.
The sulphide of zinc obtained by the methods described may be reduced to metallic
zinc by the well known methods; or it may be treated in the manner hereinafter
described so as to fit it for use as a white pigment.
The dried precipitated zinc sulphide is mixed with about three per cent. of
sulphur and the mixture is heated in a crucible to and maintained at a dull red heat
for about thirty minutes. The contents of the crucible while still hot are thrown
into cold water. The clear water is decanted off and the zinc sulphide slowly
dried. The sulphide of zinc so treated is very dense and white and is an excellent
white pigment.
For the sake of simplicity of description we have referred only to a solution of
caustic potash as the exciting liquid of the battery and to the recovery of zinc from
the spent solution by the use among other methods of sulphide of potassium, we wish
it however to be understood that a solution of caustic soda may be employed as the
exciting liquid of the battery and in place of sulphide of potassium for the recovery of
the zine from the spent solution sulphide of sodium may be employed. The sulphide
of sodium may be prepared, purified and used in the ways herein before described with
respect to sulphide of potassium.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, we declare that we
claim as the said invention of :-
"Improvements in utilizing the residual products obtained in the working of
certain kinds of voltaic batteries".
First-The recovery of zinc contained in the spent solution of caustic potash or
canstic soda employed as the exciting liquid of the said batteries by precipitating the
said zinc in the form of sulphide of zinc either by the use of flowers of sulphur or
sulphide of potassium or sodium or sulphuretted hydrogen gas, the process being con-
ducted in the various ways hereinbefore described.
Secondly-Treating the spent or exciting liquid from the voltaic batteries after
the precipitation therefrom of the zine in the forin of sulphide of zinc by boiling the said
solution with caustic lime for the purpose of removing any carbonic acid which may
have been absorbed from the air during the working of the battery and thereby
revivifying or rendering the liquid so treated suitable to be re-used in a voltaic
battery the process being conducted substantially in the manner hereinbefore
described.
Thirdly-Treating the sulphide of zinc obtained by precipitation from the spent
solution of caustic potash or caustic sod of vollaic batteries by the process or processes
herein before described; that is to say, by boiling the liquid in which the precipitate
is suspended before separation by filtration or decantation and afterwards heating the

page_text: washed and dried sulphide with free sulphur so as to give the density and whiteness
necessary to fit it for use as a white pigment substantially as hereinbefore
described.
DLM and day of May 1907