IMPROVEMENTS IN THE METHOD OF SEPARATING GLYCERINE FROM SPENT SOAP LYES, SALINE, AND OTHER SUBSTANCES, AND IN APPARATUS THEREFOR."
Year: 1881

page_text: LETTERS PATENT to Francis Joseph O'Farrell, F.C.S., of Dublin, in the County
of Dublin, Ireland, for an Invention of "IMPROVEMENTS IN THE METHOD OF
SEPARATING GLYCERINE FROM SPENT SOAP LYES, SALINE, AND OTHER
SUBSTANCES, AND IN APPARATUS THEREFOR."
PROVISIONAL SPECIFICATION left by the said Francis Joseph O'Farrell
at the Office of the Commissioners of Patents on the 27th July 1881.
_FRANCIS JOSEPH O'FARRELL, F.C.S., of Dublin, in the County of Dublin, Ireland.
"IMPROVEMENTS IN THE METHOD OF SEPARATING GLYCERINE FROM SPENT SOAP
LYES, SALINE, AND OTHER SUBSTANCES, AND IN APPARATUS THEREFOR."
The object of my Invention is the separating of glycerine from salt, caustic and
carbonated alkalies, with which it is usually found mixed in the spent lyes of soap
works, and also the recovery and utilization of the same products with a view to
lessening the cost of the production of glycerine.
The method by which I propose to separate the glycerine from the impurities
with which it is usually mixed in spent soap lyes is as follows:-
The tallow, palm oil, or other neutral fat, which is generally used in the manu-
facture of soap, is saponified in the ordinary manner by means of soluble caustic
alkalies of the required density. When saponification is complete the glycerine is
separated from the stearate and oleate of soda or soap, together with the excess of
water, caustic and carbonated alkalies, by means of common salt.
Now I propose to evaporate the spent soap lyes thus obtained (immediately it is
drawn off from under the soap) by means of fire or dry steam, during which
operation I prefer to use a steam jacketed pan till a saturated aqueous solution of
common salt is obtained, which can easily be ascertained by determining its specific
gravity by means of a hydrometer, and having obtained this saturated solution of
salt, in which is held the glycerine, I proceed to treat the solution (with the
addition of a small quantity of salt) to separate the glycerine from a fresh portion
of soap, and to re-evaporate the spent soap lyes till it is again saturated with

page_text: common salt, and I continue to use the spent lyes till the quantity of glycerine
present therein is sufficient to be conveniently and economically separated.
Having thus obtained the maximum amount of glycerine in the minimum volume
of spent soap lyes, I proceed to evaporate the solution till as much salt as possible
crystallizes out; I then dissolve out the glycerine from the residue by means of
methylated spirits or other suitable liquid, or I may at once separate the glycerine
by means of distillation in vacuo.
In carrying out my said Invention I propose to use apparatus consisting of a
condenser and two receivers, the latter being connected with the condensing worm
by means of a "two way" cock or other suitable valve, in such a manner that the
first portion of the distillate, consisting, chiefly of water, will be received in one
receiver, and the second portion, consisting entirely of glycerine, will be received in
the second receiver.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Francis Joseph O'Farrell in the Great Seal Patent Office on the
25th January 1882.
FRANCIS JOSEPH O'FARRELL, F.C.S., of Dublin, in the County of Dublin, Ireland.
"IMPROVEMENTS IN THE METHOD OF SEPARATING GLYCERINE FROM SPENT SOAP:
LYES, SALINE, AND OTHER SUBSTANCES, AND IN APPARATUS THEREFOR."
į
The object of my Invention is to effect the separation of glycerine from the salt,;
caustic and carbonated alkalies with which it is mixed in the spent lyes of soap
works, and also the recovery and utilization of the salt, caustic and carbonated.
alkalies with a view to lessening the cost of the production of the glycerine.
The method by which I carry out my Invention is as follows:-
The tallow, palm oil, or other neutral fats which are generally used in the manu-
facture of soap are saponified in the ordinary manner by means of soluble caustic.
alkalies of the required density. When saponification is complete the glycerine is.
separated from the stearate and oleate of soda (or soap), together with the excess
of water, caustic and carbonated alkalies, by means of common salt.
Now I propose to evaporate the spent lye thus obtained immediately it is drawn,
off from under the soap by means of fire heat or dry steam applied by any suitable
apparatus till a saturated aqueous solution of common salt is obtained (which
can readily be ascertained by determining its specific gravity by means of an.
hydrometer), and this saturated solution I proceed to use for the purpose of
separating the glycerine from a fresh portion or second charge of soap, when I
again evaporate the spent lye obtained from this fresh portion or second charge in
the manner applied to the lye obtained from the first charge of soap, and I
again return the aqueous solution thus obtained to the soap for the purpose of
separating the glycerine from a third charge, when I again evaporate the lye
obtained therefrom and proceed as before, thus repeating the process in this manner
until the quantity of glycerine present in the solution is sufficiently concentrated
to be economically separated.
Having by this means obtained the maximum amount of glycerine in the
minimum volume of spent lyes, I proceed to evaporate the solution till as much
salt as possible crystallizes out, when there remains only glycerine containing a
small portion of water which I eliminate by distilling the glycerine in vacuo,
during which operation I introduce a jet of steam at about 200° centigrade, or as
nearly as practicable of the same temperature as the liquid under treatment, by
which means I secure a perfectly uniform ebulition during the distillation.
For the purpose of carrying on the distillation in vacuo propose to use apparatus
as illustrated in the accompanying Drawing, consisting of two receivers or
chambers A and B connected by a cock C, one chamber communicating with the
still and both communicating with an air pump, as shown, which communication is
controlled by the cocks E and F.
Now the first portion of the distillate, which consists entirely of water, passes
into the receiver or chamber A, thence to the receiver or chamber B, and when the
last portion of water is passed over, cock C is closed and the water is drawn off
at D. Immediately the water is drawn off from chamber B the cock E commu-
nicating with the air pump is slowly opened till a vacuum is re-established in
chamber B, when cock C is again opened to allow the flow of glycerine which now
takes place, it being understood that water will distil over at about 45° centigrade,
whereas the glycerine distils at a temperature of 180° centigrade. When the
glycerine passes over it is mixed with a small quantity of the steam used for the
purpose of creating uniform ebulition; and to eliminate this small portion of steam

page_text: I re-distil the glycerine, during which re-distillation I propose to use external
heat only.
In carrying out my said Invention the following advantages are obvious:-
Firstly. The aqueous solution of salt obtained by the evaporation of the spent
lye may be used over and over with fresh charges of soap, ad libitum, thus
enabling the treatment of the lye to be carried on in a continuous manner.
Secondly. By this treatment the excess of caustic soda as usually used in present
methods of separating lye is saved.
Thirdly. One supply of common salt is rendered sufficient for an indefinite
period, while by the present method a supply is necessary with each charge of
soap.
Fourthly. The small portions of soap held in suspension in the lye are recovered'
by my process.
Having thus described the nature of my said Invention, and the manner of
applying the same in practice, I would have it understood that what I consider
new and useful, and therefore claim as the Invention to be secured to me by the
herein before in part recited Letters Patent is,―
.
Firstly. The method of treating soap lye by fire heat or dry steam until an
aqueous solution of common salt is obtained, and using this solution for the purpose
of separating the glycerine from a fresh charge of soap, thus enabling the process
to be repeated over and over until the maximum amount of glycerine is obtained
from the minimun volume of spent lye, substantially as and in the manner herein
set forth.
Secondly. The method of distillation in vacuo in combination with the
introduction of a jet of steam, substantially for the purpose herein described and
illustrated by accompanying Drawing.
In witness whereof, I, the said Francis Joseph O'Farrell, have hereunto set
my hand and seal, this Fourteenth day of January, in the year of our
Lord One thousand eight hundred and eighty-two.