THE UTILIZATION OF ALKALI WASTE, GAS LIME, OR OTHER FORMS OF LIME, FOR THE PRODUCTION OF TRI-CALCIC & DI-CALCIC PHOSPHATES."
Year: 1880

page_text: LETTERS PATENT to William Arthur Hills, of Chester Chemical Works, Saltney,
near Chester, in the County of Flint, for an Invention for "THE UTILIZATION
OF ALKALI WASTE, GAS LIME, OR OTHER FORMS OF LIME, FOR THE PRODUCTION
OF TRI-CALCIC & DI-CALCIC PHOSPHATES."
PROVISIONAL SPECIFICATION left by the said William Arthur Hills at the
Office of the Commissioners of Patents on the 13th April 1880.
WILLIAM ARTHUR HILLS, of Chester Chemical Works, Saltney, near Chester, in
the County of Flint. "THE UTILIZATION OF ALKALI WASTE, GAS LIME, OR OTHER
FORMS OF LIME, FOR THE PRODUCTION OF TRI-CALCIC & DI-CALCIC PHOSPHATES."
This Invention has for objects the utilization of the tank waste produced in the
manufacture of alkalies of gas lime, or other forms of lime, by a novel application
of the hypo-sulphite and sulphite of lime for the production of tri-calcic and dicalcic
phosphates.
1. It is well known that the insoluble sulphide of calcium, which is the chief
constituent of tank waste, can be converted by oxidation, by air or otherwise, into
poly-sulphides, hypo sulphite, sulphite and sulphate of lime, which are more or less
soluble in water. The solution thus obtained may be advantageously applied to the
decomposition of phosphate of soda or potash, forming poly sulphides, hypo sulphite,
or sulphite of soda or potash, and phosphate of lime. By this means the soda or
potash is recovered in a more valuable form than it is when the phosphates of soda
or potash are decomposed in the ordinary way by chloride of calcium, and phosphate
of lime of high strength is obtained.
2. Ordinarily the oxidation of the tank waste is carried on by the aid of air to
such a point that poly sulphide and hypo sulphite of lime are formed, and as little
sulphite and sulphate of lime as possible, the recovering of the sulphur being the
object, but for this purpose it is preferable to carry on the oxidation until the
whole of the poly-sulphides are converted into hypo sulphite and sulphite of lime,
which may be conveniently done by leading sulphurous acid gas (with or without
the products of combustion from furnaces) together with air through the tank
waste, which is preferably moist or suspended in water. By the use of sulphurous

page_text: acid gas the quantity of tank waste rendered soluble is much increased, and the
solution is obtained in a more convenient form for the purpose described in
paragraph 1.
3. Lime, or carbonato of lime, finely divided and held in suspension by water
may be converted into sulphito of lime by treatment with sulphurous acid gas.
4. Gas lime ore, the refuse lime from gas works may be converted into hypo
sulphite and sulphite of lime if sulphurous acid gas is led through the gas lime
when moist or held in suspension in water.
5. By the means described in the above paragraphs lime, carbonate of lime, gas
lime, or alkali waste, is converted into hypo sulphite of lime, which when applied
to the decomposition of phosphate of soda and potash enables the soda or potash to
be recovered in a more valuable form than when the decomposition is made by
means of chloride of calcium.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Arthur Hills in the Great Seal Patent Office on the 11th
October 1880.
WILLIAM ARTHUR HILLS, of Chester Chemical Works, Saltney, near Chester, in
the County of Flint. "THE UTILIZATION OF ALKALI WASTE, GAS LIME, OR OTHER
FORMS OF LIME, FOR THE PRODUCTION OF TRI-CALCIC AND DI-CALCIC PHOSPHATES."
This Invention has for its object the utilization of the tank waste produced in
the manufacture of alkalies of gas-lime, or of other forms of lime by a novel
application of the hypo-sulphite of lime for the production of tri-calcic and di-calcic
phosphates.
1. It is well known that the insoluble sulphide of calcium which is the chief
constituent of alkali waste can be converted by oxidation by air or otherwise into
polysulphides, byposulphite, sulphite and sulphate of lime, which are more or less
soluble in water; of these the sulphite and sulphate of lime are, for all practical
purposes, insoluble in water, and the poly-sulphides are unsuitable for the purposes
of this Invention owing to the precipitation of sulphur on treatment with phosphate
of soda. For the purposes of this Invention the hyposulphite of lime is the form
best adapted for use.
2. In the ordinary mode of working alkali waste the oxidation of the waste is
carried on by the aid of air to such a point that polysulphides and hypusulphite of
lime are formed, and as little sulphite and sulphate of lime as possible, the recovery
of the sulphur being the object, but for the purposes of this Invention it is preferable
to carry on the oxidation until the whole of the polysulphides of calcium is
converted into hyposulphite of lime. This can be done by continuing the blowing
of the waste, which may be moist or held in suspension in water, but preferably
moist either with air or with air and sulphurous acid gas with or without the
products of combustion from furnaces, until the sulphide and polysulphides of
calcium are converted into hyposulphite of lime. By the use of sulphurous acid
gas the quantity of alkali waste rendered soluble and available is much increased,
and a larger proportion of hyposulphite of lime is obtained. In dealing with large
quantities of waste it is almost impracticable to oxidize the sulphide and poly-
sulphides of calcium completely into hyposulphite of lime while the waste is in
the condition of a moist solid. When it has been blown, and consequently oxidized
as far as practicable in the moist state, the waste is lixiviated and the resulting
solution run off in suitable tanks. If the oxidation has been thorough this solution
is a colorless liquid consisting of hyposulphite of lime; but if the oxidation be
incomplete the liquor will be coloured yellow by the polysulphides of calcium
present. Should the poly-sulphides of calcium be present their oxidation into
hyposulphite of lime can be effected by leading sulphurous acid gas with or without
air and the products of combustion through the liquid until the whole of the
polysulphides of calcium is converted into hypo-sulphite of limo.
3. To produce tri-calcic phosphate a solution in water of tri-sodic phosphate is
obtained, and the quantity of phosphoric acid which it contains accurately
ascertained. To this is added the solution of hypo-sulphite of lime (obtained as
5 described in paragraph 2) until there are three equivalents of lime present and
available for each equivalent of phosphoric acid, or in figures, for every 71 parts of
phosphoric acid (or 164 parts of tri-sodic phosphate) there are required 84 parts of
lime (or 228 parts of hypo sulphite of lime). This solution of hypo-sulphite of lime
is added slowly to the solution of tri-sodic phosphate with continuous stirring until
the reaction is completed, at a temperature not exceeding 140 degrees Fahrenheit.
The precipitate of tri-calcic phosphate is then filtered from the solution of hypo-
sulphite of soda, and the tri-calcic phosphate is washed thoroughly to remove the

page_text: last traces of hyposulphite of soda and dried. The hypo-sulphite of soda may bo
recovered by crystallization, evaporation, or any other well known means.
4. To produce di-calcic phosphate a solution in water of disodic phosphate is
obtained, and the quantity of phosphoric acid which it contains accurately
ascertained. To this is added the solution of hyposulphite of lime until there are two
equivalents of limo present for each equivalent of phosphoric acid, or in figures, for
every 71 parts of phosphoric acid (or 142 parts of di-sodic phosphate) there aro
required 56 parts of lime (or 152 parts of hypo sulphite of lime). This process is
carried out in exactly the same manner and with the same precautions as the
production of tri-calcic phosphate. In drying the di-calcic phosphate care must be
taken that the heat be not raised to a sufficient temperature to drive off the
equivalent of hasic water which it contains, that is, the temperature must not be
higher than 260 degrees Fahrenheit.
5. Linie or carbonate of lime finely divided and held in suspension in water can
be converted into sulphite of lime by treatment with sulphurous acid gas. This
sulphite of lime, which is held in solution by excess of sulphurous acid, can be
converted into hypo-sulphite of lime, and so rendered available for this process by
digesting the sulphurous acid solution of sulphite of lime with an equivalent
quantity of sulphur at a temperature not exceeding 140 degrees Fahrenheit until
the sulphur has combined with the sulphite of lime, forming hyposulphite of lime.
6. Gas lime or the refuse lime from gas works can be converted into hypo-
sulphite of lime, and thus rendered available for this process by leading sulphurous
acid gas through the gas lime when moist or held in suspension in water.
7. Phosphate of potash or phosphate of ammonia may be substituted for
phosphate of soda, forming phosphate of lime and bypo-sulphite of potash or
ammonia.
8. By the means described in the above paragraphs lime, carbonate of lime, gas
lime, or alkali waste is or are converted into bypo-sulphite of lime, which when
applied to the decomposition of phosphate of soda enables the soda to be recovered
in a more valuable form than when the decomposition is effected by chloride of
calcium.
Having now described the nature of my said Invention, and in what manner
the same is to be performed, I declare that I claim,-
The use of hypo-sulphite of lime, obtained substantially as herein before described,
for the decomposition of phosphate of soda, and the formation thereby of tri-calcic
and di-calcic phosphate of high strength, and the recovery of the soda in the form
of hypo-sulphite of soda.
In witness whereof, I, the said William Arthur Hills, have hereunto set my
hand and seal, this Eighth day of October, in the year of our Lord,
1880.
WILLIAM ARTHUR HILLS. (L.S.)