A NEW ELECTROLYTIC TREATMENT OF SACCHARINE SOLUTIONS
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by Louis Henri Despeissis at the Office
of the Commissioners of Patents on the 28th August 1883.
LOUIS HENRI DESPEISSIS of Paris in the Republic of France, Civil Engineer
"A NEW ELECTROLYTIC TREATMENT OF SACCHARINE SOLUTIONS
Hitherto the complete extraction of sugar from saccharine solutions has been
rendered very difficult on account of the presence of salts of the alkalies and
alkaline earths which tend to prevent and in some cases absolutely stop the
crystallization of the sugar contained in these solutions.
My process or invention has for its object the removal and separation of those
saline and earthy constituents, and the consequent liberation of the sugar which
they prevent from crystallizing and which can thus be extracted with comparative
ease and economy.
A further advantage which I claim for my invention resides in the fact that the
so called impurities of the sugar consisting principally in salts of potash are of great
commercial value and that by my process they are preserved and can be concen-
trated or sold as bye-products at a great profit to the manufacturer who thus derives
two saleable and valuable products, even from residues, such as molasses, which are
very often next to valueless.
The modus operandi is as follows: it is well known that when an electric
current is passed through a liquid containing salts in solution, an electrolytic action
takes place, and the base or metal goes to the negative pole, while the acid remains
at the positive.
If a porous partition is interposed between the two poles so as to allow the
passage of the current, but preventing at the same time the too rapid admixture of
the two liquids, then the two constituents of the salts, namely the acid and the
metal will be completely separated and will not unite readily again.
I take advantage of this fact in my invention to rid the saccharine solution of
the alkaline salts which they contain. These salts are present chiefly in the state
of carbonates and saccharates under the action of the electric current they are
electrolysed.
The carbonic acid of the sugar remaining at the positive pole while the alkaline
metal is carried to the negative pole, which is enclosed in a porous vessel or
compartment.

page_text: The alkaline metal liberated at the negativo electrode there comes in contact
with pure water, with which the vase is filled and decomposes the water, forming
caustic hydrates of the alkalies whilst hydrogen is evolved.
The current employed for this purpose can be obtained through any of the
ordinary means, such as chemical and thermic batteries, dynamo-electric machines
and so forth.
The electrodes can be made of any suitable conductive material such however as
are not attacked by the current, by introducing fresh metallic salts in solution.
Platinum and carbon electrodes are preferably to be used. The porous partitions
and vessels separating the original saccharine solution from the water destined to
collect the alkalies, can be made of porous earthenware, parchment paper, wood,
carbon, or any other suitable porous material.
Some of these materials have also the advantage of uniting a dialysing action, by
osmose, to the electrolytic action of the current.
The carbonic acid given off at the positive electrode remains partly in solution
and is partly evolved. It has however no detrimental action on the saccharose and
can be easily neutralized by the admixture of lime or other suitable earthy alkali
as it is done at the present time, with this advantage however that if the solution
is warm and diluted to the proper strength, the nascent carbonic acid will not only
neutralize the alkaline earth by the formation of an insoluble carbonate, but will
carry down the coloring matter.
The sirup and molasses can be worked warm. This process has the double
advantage of increasing their fluidity without any addition of water, thereby
lessening their resistance to the passage of the current and also still further
lessening their electric resistance through the very increase in the temperature,
thus producing a double action highly favorable to the rapid and satisfactory
working of my process.
This increase in the temperature also facilitates the escape of gases which are
thereby provented from collecting at the electrodes. This last point is also of
much practical importance.
It is desirable at times when the water surrounding the kathode gets too much
saturated with alkalies, the salts diffusing out as fast as they are introduced, to
pump it out and replace it by pure water so as to continue the operation and
remove a further quantity of the alkalies.