Improvements in the Production of Glycerine and Caustic Soda from Soap Lyes.
Year: 1896

page_text: Date of Application, 19th May, 1896-Accepted, 18th July, 1896
COMPLETE SPECIFICATION.
Improvements in the Production of Glycerine and Caustic Soda
from Soap Lyes.
We JOSEPH GLATZ, Chemist, of 485 Kent Avenue, Brooklyn, and ORAZIO
LUGO, Chemist, of 182 John Street, New York, both in the United States of
America 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 :-
This invention relates to the production of glycerine and caustic soda from
soap lyes.
After the saponification of the fats in the manufacture of soap, and the
elimination of the solids formed, there is left a liquor commonly known as soap
lye, which contains free alkali; sodium or potassium hydrate; fats which are the
glycerides of the fatty acids; free glycerine; and some of the fatty acids.
The object of the present invention is to provide means whereby all the free
alkali may be extracted from soap lyes, the alkali salts decomposed, and the caustic
soda thus set free, extracted. Further the object of the invention is to provide
means whereby clarification of the lye solution may be accomplished by the
precipitation of the albuminoidal matters and other impurities, and by the decom-
position of the glycerine containing compounds, setting free a large amount of
available glycerine, which after distillation shall be of such purity as to render it
available for all practical purposes, especially for the manufacture of high
explosives.
The present invention consists essentially in the method of treating soap lyes
by subjecting the same to the action of a current of electricity, the anode being
composed of zinc or carbon, preferably the latter, retained in contact with the
liquor under treatment. Further the invention consists in the method of treating
soap lyes which consists in subjecting the same to a current of electricity, the
current being applied by means of an anode of zinc or carbon separated from the
cathode by a porous partition.
In carrying my invention into practical effect I preferably proceed substantially
as follows:
A tank or trough which in form is preferably long and narrow, is divided into
compartments projecting into the main body of the tank by partitions of sandstone
or marble. Each alternate compartment is preferably arranged on the opposite
side of the trough or tank to that of the adjacent compartments and extends only
partially across the tank or trough, leaving a tortuous passage from one end to
the other of the tank around the compartments. In the passage thus formed are
arranged a number of electrodes, which form the anodes of the electric current,
and arranged in each of the compartments is an electrode forming the cathode of
the electric current. The electrodes are placed sufficiently near together to offer
the least possible resistance to the passage of the current. The anodes and the
cathodes are connected respectively in multiple arc with a suitable source of
electricity.
In an apparatus of this kind the soap lye to be treated is introduced at one end
and allowed to flow slowly through the tank, the tortuous passage through which
it moves insuring contact with a large amount of electrode surface, and is discharged
at the other end. Each cathode compartment is supplied with a quantity of pure
water which surrounds the cathode, and when the soap lye passes through the

page_text: tank and a current of electricity is passed from the anodes through the soap lye,
through the partitions, the water in the cathode compartment, and thence through
the cathode back to the source of the current, the following action will take place:
The caustic soda in the electrolyte, namely the soap lye, is decomposed by the
action of the electric current and the sodium is attracted to the cathode where it
immediately becomes oxidized by taking up one atom of oxygen from the water,
forming oxide of sodium. This combines with one molecule of water, forming
sodium hydrate or caustic soda.
The action of the current is to decompose the glycerine compounds simultaneously
with the extraction of the caustic alkali, setting free the glycerine which now
becomes available. The albuminoidal and coloring matters are rendered insoluble
and may be easily removed by filtration. The color of the soap lye treated is
changed from a dark brown to a light straw yellow, and the glycerine contained
in the lye and set free as described, is ren lered perfectly transparent.
After the lye is treated electrolytically as described, the insoluble matter is
separated from the liquor and the latter is distilled. The glycerine obtained will
be perfectly pure and free from all discoloration, and can be applied for any and
all purposes in the arts.
The caustic soda produced is practically pure and can be used immediately by
the soap maker, it being possible by my process to produce the alkali solution
of the density required for this use.
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. The method of eliminating the caustic alkali and the recovery of the
glycerine contained therein, which consists in subjecting the liquor to the action
of a current of electricity, the an de being composed of zinc or carbon and being
retained in contact with the liquid being treated, substantially as described.
2. The method of eliminating the caustic soda from soap lyes and the decom-
position of the glycerine compounds contained therein, which consists in subjecting
the lyes to the action of a current of electricity applied by means of an auode of
carbon or zinc retained in contact with the liquor, and the cathode separated from
the anode by a porous partition, substantially as described.
Dated this 19th day of May 1896.
WHEATLEY & MACKENZIE,
40 Chancery Lane, London, W.C., Agents.