Improvements in or relating to the Manufacture of Chlorates.
Year: 1893

page_text: Date of Application, 19th May, 1893-Accepted, 8th July, 1893
COMPLETE SPECIFICATION.
Improvements in or relating to the Manufacture of Chlorates.
A communication from ALWIN NIESKE, of Dresden, Saxony, in the German
Empire, Proprietor of the Chrome and Aluminium Works at Alt-Herzberg.
I, ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex,
Chartered Patent Agent, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
The manufacture of chlorates as at present carried out is effected by the
decomposition of chlorate of potassium by a very complicated and expensive
process in which the last mentioned salt is manufactured by saturating lime-milk
with chlorine whereby chloride of calcium and chlorate of lime are produced. By
mixing the liquid with chloride of potassium the chlorate of lime is decomposed
into chlorate of potassium and chloride of calcium. The clarified liquid. is then
evaporated and the chlorate of potassium is obtained by crystallization. If the
chlorate of potassium is manufactured in this manner a considerable quantity
(15 per cent.) of this salt remains in the lyes of chloride of calcium and is thus
completely lost, while the lyes are also quite worthless.
These great losses of the valuable salt may be avoided by carrying out the
process in the following manner;—
At first lime-milk (caustic lime) is saturated with chlorine and then the necessary
quantity of chloride of potassium is added. Then the clarified or filtered liquid at
a suitable high temperature is mixed with a quantity of sulphate of soda corre-
sponding with the quantity of chloride of calcium contained in the liquid, and the
white gypsum which has generated is filtered in a filter-press, washed and may be
afterwards employed as gypsum. The filtrate which now contains chlorate of
potassium and chloride of sodium, is evaporated in kettles or pans, the precipitating
chloride of sodium is baled out with perforated ladles, expressed by centrifugal
action and well-washed. The lyes treated in or recovered from the centrifugal
apparatus and wash-waters return to the evaporating kettle. The salt treated in or
recovered from the centrifugal apparatus may be employed for any desired purposes.
When the lye is sufficiently evaporated, it is poured into suitable kettles for crystal-
lization. After some time the crystals of chlorate of potassium are withdrawn,
The
treated in centrifugal apparatus, washed and treated in the usual manner.
mother-lyes, the lyes treated in the centrifugal apparatus and the wash-waters
always return to the evaporating kettles. A second crystallization which was
necessary in the former process is no further required, as the first crystallization
is sufficient. As in this process no lyes are lost, they being always re-evaporated
it is obvious that no losses of chlorate of potassium take place.
The decompositions which take place are expressed by the following equations ;-
I. 6 Ca (OH)2+6 Cl₂=Ca (CIO3)2 +5 CaCl2+6 H₂O
II. Ca (ClO)+5 CaCl2+2 KCl=2 KCIO,+6 CaCl,
III. 2 KCIO₂+6 CaCl₂+6 Na₂SO₁=2 KClO3+12 NaCl + 6 CaSO.
If it be desired to manufacture chlorate of sodium instead of chlorate of
potassium which former was hitherto obtained in a very complicated manner by
means of silico-fluoric acid the lime-milk which is saturated with chlorine is mixed
with chloride of sodium instead of chloride of potassium and then the process is
continued in the same manner as when manufacturing chlorate of potassium. It
will be advantageous, however, to immediately add to the chlorinated lime-milk a

page_text: chloride of calcium and calcium chlorate present therein. This is expressed by the
following equation ;-
Ca (ClO)+5 CaCl, +6 NaSO,-2 NaCIO,+ 10 NaCl +6 CaSO..
It will be easy to get from the chlorate of sodium all other chlorates by
decomposition with the corresponding chlorides and sulphates, for instance
2 NaClO3+ BaCl,=2 NaCl+Ba (ClO3), or
6 NaCIO,+ Fe, (SO4)3=Fе2 (CIO) +3 Na₂SO, etc.
Instead of caustic lime (hydrate of lime) caustic baryta (hydrate of baryta) or
caustic strontium (hydrate of strontium) may be employed in which case chloride
of sodium and sulphate of baryta ("blanc fix ") or sulphate of strontium are
obtained as by-products. This is expressed by the following equations ;-
I. 6 Ba (OH)2+6 Cl₂=Ba (ClO3)2+5 BaCl₂+6 H₂O
II. Ba (ClO3)2+5 BaCl₂+2 KCl=2 KCIO,+6 BaCl,
-
III. 2 KCIO,+6 BaCl2 + 6 Na2SO4=2 KCIO₂+12 NaCl +6 BaSO₁, or
I. 6 Sr (OH),+6 Cl₂=Sr (ClO3)2+5 SrCl₂+6 H₂O
II. Sr (ClO3)2+5 SrCl)2+2 KCl=2 KCIO,+6 SrCl₂
III. 2 KCIO,+6 SгCl₂+6 Na₂SO,=2 KClO3+12 NaCl+6 SrSO.
3
Having now particularly described and ascertained the nature of the said inven-
tion as communicated to me by my foreign correspondent, and in what manner the
same is to be performed I declare that what I claim is ;-
The process of manufacturing chlorates especially chlorate of potassium and
chlorate of sodium by decomposing chloride of calcium chloride of baryta or
chloride of strontium by means of sulphate of sodium and simultaneously obtaining
chloride of sodium and gypsum or sulphate of baryta or sulphate of strontium
substantially as described.
Dated this 19th day of May 1893.
W. P. THOMPSON & BOULT,
Agents for the Applicant.