improvements in the Process of Obtaining Ohlorates of the Alkalles or of the Alkaline Earth Metals by Electrolysis.
Year: 1893

page_text: Date of Application, 7th Mar., 1893-Accepted, 8th Apr., 1893
improvements in the Process of Obtaining Ohlorates of the Alkalles
or of the Alkaline Earth Metals by Electrolysis.
We, WILLIAM TAYLOR GIBBB, Chemist, and STANISLAUS PASOHAL
FRANOHOT, Civil Engineer, both of Buckingham in the County of Ottawa, in
the Province of Quebec and Dominion of Canada, do hereby declare the nature of
our invention for "IMPROVEMENTS IN THE PROCESS OF OBtaining CHLORATES
OF THE ALKALIES OR OF THE ALKALINE EARTII METALS BY ELECTROLYSIS,
and in what manner the same is to be performed, to be particularly described and
ascertained in aud by the following statement :-
"
Our invention relates to the manufacture of chlorates of the alkalies or of the
alkaline earth metals, such as clilorate of potash, by electrolytic action.
The object of our invention is to reduce the cost of manufacture.
In the electrolytic processes hitherto used, provision was not made for getting
rid of the hydrogen evolved and for that reason such processes were always
useless, the product being reduced again by the hydrogen which came off at the
kathode. This objection was overcome in one process by the use of a porous
diaphragm between the anode and the kathode at the expense of an increase in the
voltage of the electric current necessary for the process. In our improved
process the hydrogen is consumed at the kathode in the nascent state furnishing
some of the heat required and the necessity of a diaphragm is dispensed with,
thus permitting the use of a current of low voltage and thereby reducing the
cost.
Our process for the manufacture of chlorate of potash consists in passing an
electric current through a solution of potassiuni chloride, contained in an electro-
lytic cell of ordinary construction, having an anode of carbon, platinum or other
substance which will not be acted upon by chlorine, and a kathode consisting of a
metallic oxide which will readily yield up its oxygen in the prosence of nascent
hydrogen. Such a one we find oxide of copper to be and which we use by
preference, forming the same into a plate by means of plastering it on to wire
netting or in some other convenient manner. Chlorine being set free at the anode
and the metal potassium at the kathode, the potassium at once reacts upon the
water, displacing one atom of hydrogen and forming potassium-hydroxide or what
is commonly called caustic potash. The displaced hydrogen immediately combines
with the oxygen of the' copper oxide to form water, reducing the kathode to
metallic copper and thus never allowing the hydrogen to become actually freo and
it can therefore never exert a reducing action on the hypochlorite or chlorate
which is formed. When the whole of the oxide of copper in the kathode has
been reduced to metallic copper, the kathode is removed from the coll and washed
in water until it is perfectly free from all traces of potassium salts, then dried-and
heated to a dull red heat in a current of atmospheric air, by which means the
copper at once becomes re-oxidised, i.e. converted into oxide of copper again and is
again ready to be replaced in the electrolytic cell. This operation of reduction
and reoxidation may be repented ad infinite number of times. The proportion
between the cell and kathode is so arranged that by the time the kathode is
reduced to metallic copper, about one half of the potassium chloride in 'solution
has been converted into potassium chlorate. The solution is then drawn off' from
the cell and run into crystallizing tanks. On cooling, the potassium chlorate
separates in crystals, leaving the undecomposed potassium chloride in solution.
This solution is then drained off from the crystals, made up to its original strength
again with fresh potassium chloride and returned to the cell which has been fitted
with the re-oxidised kathodes and again subjected to the action of the electric
AVERASt

page_text: The reactions during the process are as follows: On the passage of the electric
current tho potassium chloride is decomposed into potassium and chlorine, thus:
2 KCI = K, + Cl. The potassium at the kathode at once reacts upou the water
thus K, 2H,O=2 KHO + H,. This hydrogen at once reacts upon the
oxide of copper of the kathode thus: H, + CuO=H,O + Cu. The caustic
potash in solution then comes in contact with the chlorine which is being evolved
at the anode and the following reaction takes place: 2 KHO + Cl, = KCl +
H₂O + KCIO. When the solution in the cell attains the necessary temperature,
the hypochlorite of potassium (KCIO) decomposes as follows: 3 KCIO 2 KCl +
KCIO,, thus forming potassium chloride and potassium:
It is to be noted that in other processos the heat necessary to decompose the
hypochlorito of potassium into potassium chloride and chlorate was generated by
forcing through the cell a large current of electricity, or was supplied from an
external source whereas in our process this necessary heat is generated by the com-
bustion of tho hydrogen which takes place when combining with the oxygen of the
oxide of copper kathode. The hydrogen which therefore would in other processes
be wasted is thus utilized and made to reduce the quantity of electricity
otherwise necessary to produce heat, and as the electrodes are placed close
together, a current of less intensity or of lower voltage will suffice, a distinct saving
being thus affected.
The above describes the process of manufacture of potassium chlorate, which
has been chosen as an example for illustration. The process is however not con-
fined to potassium chlorate but is equally applicable to the manufacture of the
chlorates of any of the alkalies or alkaline earth metals.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what
we claim is :
1. A process of obtaining chlorate of an alkali or alkaline earth metal by
electrolysis, consisting in subjecting a solution of its chloride to the action of an
electric current in a cell having an oxido of copper kathode until about one half of
the chloride in said solution is decomposed and converted into chlorate, drawing
off the solution into crystallizing tanks and allowing it to cool and crystallize, then
drawing off the remaining liquor, making up its strength with fresh chloride and
returning it into the cell, removing the kathode from the cell, washing, drying,
reoxidizing and replacing it, substantially as set forth.
2. As part of a process for the manufacture of chlorate of one of the alkalies or
alkaline earth metals by electrolysis, the subjecting of a solution of chloride of
said alkali to the action of an electric current in a cell having a kathode composed
of an oxide which readily yields up its oxygen in the presence of nascent hydrogen,
substantially as set forth.
3. A process of manufacturing chlorate of potassium by electrolysis, consisting
in subjecting a solution of chloride of potassium to the action of an electric current
in a cell having an oxide of copper kathode until about one half of the potassium
chloride in said solution is decomposed and converted into potassium chlorate,
drawing off the solution into crystallizing tanks and allowing it to cool and
crystalize, removing the kathode from the cell, washing, drying, reoxidizing and
replacing it, drawing off the remaining liquor from the crystalizing tank, making
up its strength with fresh ohloride and returning it into the cell to repent the process,
substantially as set forth.
L