Improvements in the Treatment of Tanning Liquids for Clarifying, Bleaching, or Decolourizing them.
Year: 1897

page_text: Date of Application, 20th May, 1897
Complete Specification Left, 24th Dec., 1897-Accepted, 26th Feb., 1898
PROVIDIONAL SPECIFICATION.
Improvements in the Treatment of Tanning Liquids for Clarifying,
Bleaching, or Decolourizing them.
I, PERCY GERALD SANFORD, of 20, Cullum Street, in the City of London, Fellow
of the Institute of Chemistry, Analytical and Consulting Chemist and Assayer, do
hereby declare the nature of this invention to be as follows:
My invention has for its object to effect the clarifying, bleaching, or decolour-
izing of tanning liquids more efficiently, expeditiously and economically than
has hitherto been attained.
It has been proposed to treat tanning liquids or liquids intended for the pro-
duction of what is known as tanning extract, by means of albuminous
matter, which, on coagulation, precipitates, and carries down with it,
colouring, or other matter which it is desirable to remove. As hitherto conducted
the process has not been efficiently performed owing to a considerable amount of
albumen being held in solution, this albumen, or the products derived therefrom,
on account of the liquor in question being treated with sulphuric acid, sulph-
hydrate of ammonium, or the like, afterwards giving rise to injurious or objection-
able chemical action, resulting in, or through the generation of gases and other
injurious products thereby causing injury, and clogging of the filters where filters
are used, and impeding the breaking up of the coagulum, or coagulated material,
thereby preventing, or impeding, the separation of the coagulum by means of
decantation, and incrusting, and diminishing the effectual working of, the con-
centrating apparatus through which the tanning liquors are passed subsequently
to the treatment with albumen, as well as causing waste of albuminous matter.
According to my invention I overcome these objections by adding to the aforesaid
tanning liquors together with the albuminous matter (which may be of animal, or
vegetable, origin) an alkaline fluoride, preferably ammonium fluoride, or boro-
fluoride of an alkali, or equivalent agent, which, on the application of heat, or on
the addition of piero-citric acid, will cause the albumen to be completely, or prac
tically completely, coagulated.
The coagulated albumen precipitates and carries down with it, out of the super-
natant liquid, colouring matter, or other matter, the removal of which is the object
of the process, the whole, or practically the whole, of the albumen being coagu-
lated and precipitated by the means described. The precipitated matter, and the
decolourized, clarified, or bleached, supernatant liquor, are separated by filtration,
decantation, or other suitable means, and the liquor can be concentrated in the
usual, or any suitable manner. I prefer to heat the liquor up to, or about, the
same temperature as that of the concentrators, before it passes thereinto, in order
not to cool the liquor undergoing such concentration and cause the formation of
insoluble anhydrides of the tannin.
The water used for the purpose of effecting the infusion of the matter containing
tannin, after the removal of obnoxious bi-carbonates, is preferably treated by means
of an agent for the purpose of destroying injurious germs, or otherwise preventing
the developement of nascent gases, or the precipitation of objectionable bases of

page_text: elementary substances which are conducive to the production of acetous, or other,
fermentative action. Suitable agents for this purpose are hydrofluoric acid, an
alkaline fluoride, boracic acid, or borate of sodium, or potassium, or both the fluoric
and boracic compounds may be used. The infusion of tanning matter obtained
is run off into a vat and subjected to the treatment herein before described.
1007
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.
Improvements in the Treatment of Tanning Liquids for Clarifying,
Bleaching, or Decolourizing them.
I, PERCY GERALD SANFORD, of 20, Cullum Street, in the City of London, Fellow
of the Institute of Chemistry, Analytical and Consulting Chemist and Assayer, 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:-
My invention has for its object to effect the clarifying, bleaching, or decolour-
izing of tanning liquids more efficiently, expeditiously and economically, than
has hitherto been attained.
It has been proposed to treat tanning liquids, or liquids intended for the pro-
duction of what is known as tanning extract, by means of albuminous
matter, which, on coagulation, precipitates, and carries down with it,
colouring, or other, matter which it is desirable to remove. As hitherto conducted
the process has not been efficiently performed owing to a considerable amount of
albumen being held in solution, this albumen, or the products derived therefrom,
on account of the liquor in question being treated with sulphuric acid, sulph-
hydrate of ammonium, or the like, afterwards giving rise to injurious, or objection-
able, chemical action, resulting in, or through, the generation of gases, and other
injurious products, thereby causing injury, that is loss of tannin, and clogging, of
the filters, where filters are used, and impeding the breaking up of the coagulum,
or coagulated material, thereby preventing, or impeding, the separation of the
coagulum by means of decantation, and incrusting, and diminishing the effectual
working of, the concentrating apparatus through which the tanning liquors are
passed subsequently to the treatment with albumen, as well as causing waste of
albuminous matter. According to my invention I overcome these objections by
adding to the aforesaid tanning liquors together with the albuminous matter
(which may be of animal, or vegetable, origin) an alkaline fluoride, preferably
ammonium fluoride, or boro-fluoride of an alkali, or equivalent agent, which, on
the application of heat, or on the addition of picro-citric acid, will cause the albumen
to be completely, or practically completely, coagulated.
The coagulated albumen precipitates and carries down with it, out of the super-
natant liquid, colouring matter, or other matter, the removal of which is the object
of the process, the whole, or practically the whole, of the albumen, being coagu-
lated and precipitated by the means described. The precipitated matter, and the
decolourized, clarified, or bleached, supernatant liquor, are separated by filtration,
decantation, or other suitable means, and the liquor can be concentrated in the
usual, or any suitable, manner; I prefer to heat the liquor up to, or about, the
same temperature, as that of the concentrators, before it passes thereinto, in order
not to cool the liquor undergoing such concentration and cause the formation of
insoluble anhydrides of the tannin.

page_text: The water used for the purpose of effecting the infusion of the matter contain-
ing tannin, after the removal of obnoxious bi-carbonates, sulphates and organic
matter of an injurious nature, is preferably treated by means of an agent for the
purpose of destroying injurious germs, or otherwise preventing the developement
of nascent gases, or the precipitation of objectionable bases of elementary sub-
stances which are conducive to the production of acetous, or other, fermentative
action. Suitable agents for this purpose are hydrofluoric acid, an alkaline fluoride,
boracic acid, or borate of sodium, or potassium, or both the fluoric and boracic
compounds may be used by adding the same to the wood or other materials under-
going, or to undergo extraction. The infusion of tanning matter obtained is run
off into a vat and subjected to the treatment herein before described.
In order that my invention may be well understood I will now give several
examples of the best methods with which I am acquainted for carrying it into
effect premising that I do not limit myself to the precise details given by these
examples.
EXAMPLE 1. The treatment of tanning liquors by means of a vegetable
albuminous matter and ammonium fluoride.
The decolourizing solution may be made as follows:-One part by weight of
ammonium fluoride is dissolved in water at 25°-35° Centigrade and this is added
to 150 parts by weight of bran or other vegetable albuminous matter, and the mash
is placed in a dialyser, or it is extracted under pressure. The vegetable matter is
then pressed and the liquor is filtered. Boracic acid may be added, this being done
preferably after dialysis is complete.
Having determined the strength of the solution of albumen (i.e. the quantity of
albumen or active material present in the solution) it is added to the solution of
annin. It is recommended that the density and the temperature of the two solutions
should be as nearly as possible the same, in order to avoid "chill" in the albumen
solution on coming into contact with the tannin solution. Stirring is then effected
so as to cause complete mixture, and the temperature is raised to about 65° Centi-
grade when coagulation takes place. The vat in which the process takes place
should be of such a size that the loss of temperature does not exceed 3°-4° Centi-
grade in from 3 to 4 hours, especially when the liquor is to be separated by
deposition, rather than filtration.
EXAMPLE 2. The treatment of tanning liquors by blood and ammonium fluoride.
When blood or animal albumen is used, it may be prepared by treatment with
fluoride of ammonium or the like as described in the Specification of my application
for Letters Patent No. 12449 of even date herewith.
The tanning liquor from the maxeration or decoction, is passed over a suitable
cooler when it is cooled down to 20°-25° Centigrade one quarter to one half of a
litre of the decolorant per hecto litre of liquor to be decolourized. Thus 100 litres
of liquor at 250° Baume weighing 101700 grams at 15° Centigrade
(water being taken as 1000) require from 254 to 5.10 grams of decolo-
rant of an equal density. The addition of the decolourant may be conveniently
made as the liquor is running into the vat which ensures complete mixture when
properly conducted, when there is added a strong solution of picro-citric acid, made
by dissolving 10 parts of picro-citric acid, and 20 parts of citric acid in 770 parts
of water. The quantity of this solution which it is necessary to add is from th
to th part of the total quantity of active material contained in the decolorant.
The object of the picro-citric acid is to rid the liquor of all traces of existing
albumen or other precipitable substances without having recourse to ebullition.
This process although effectual in the case of liquors of from 1° to 25° Baume is
not applicable to those of a higher density.
When heat is used in place of picro-citric acid the cooled liquor is treated as
described by means of the decolorant and well mixed, the temperature is then raised
to effect coagulation which takes place at about 63° Centigrade at which tem-
perature it is maintained for about 3 hours. The coagulated material having
subsided the clean liquor is withdrawn to the concentrators, the liquor including

page_text: the deposit in the decolourizing vat passing to the filter press. If the liquor prior
to decolourizing be acid it should be partially neutralised, and this may be effected
in the following manner. The acidity is determined and may be calculated as
sulphuric acid (H₂SO).
Solution for neutralising acidity:
Sodium borate 37'5 grams.
Sodium hydrate 09 grams.
dissolved, and made up to 1 litre with distilled water, 20 cubic centimeters of this
solution will neutralise 0196 grams of acidity calculated as (H2SO4) sulphuric acid.
In dealing with large quantities of liquor it is better to add the material in the dry
form.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:
The clarifying bleaching or decolourizing of tanning liquids by treating them
with albuminous matter together with an alkaline fluoride such as ammonium
fluoride or boro-fluoride of an alkali and subsequently causing coagulation of the
albumen by means of heat or of picro-citric acid substantially as hereinbefore
described.
Dated this 24th dur of December 1897
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.