A METHOD OR METHODS OF PURIFYING AND DECOLORISING CERTAIN GUMS
Year: 1848

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, MOSES
HAYM PICCIOTTO, of Finsbury Square, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Seventeenth day of August, in the twelfth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Moses Haym Picciotto, my exors, adñiors, and assigns, Her especial license,
full power, sole privilege and authority, that I, the said Moses IIaym Picciotto,
my exors, adñiors, and assigns, or such other as I, the said Moses Haym
Picciotto, my exors, admors, and assigns, should at any time agree with, and
no others, from time to time and at all times during the term of years therein
expressed, should and lawfully might make, use, exercise, and vend, within
England, Wales, and the Town of Berwick-upon-Tweed, in the Islands of
Guernsey, Jersey, Alderney, Sark, and Man, and in Her Majesty's Colonies and
Plantations abroad, my Invention of "A METHOD OR METHODS OF PURIFYING
AND DECOLORISING CERTAIN GUMS;" in which said Letters Patent is contained a
proviso that I, the said Moses Пaym Picciotto, shall cause a particular
description of the nature of my said Invention, and in what manner the same
is to be performed, to be enrolled in Her Majesty's High Court of Chancery
within six calendar months next and immediately after the date of the said

page_text: in part recited Letters Patent, as in and by the same, reference being thereunto
had, will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the
said Moses Haym Picciotto, do hereby declare that the nature of my
said Invention and improvements, and the manner in which the same are to
be performed and carried out, are fully described and ascertained in and by
the following description thereof, that is to say :-
It is known that gum arabic of whatever quality or from whatever
country imported, the Senegal included, contains, besides the pure substance,
called by some chemists "arabine," also more or less of all the following
impurities, viz., ligneous and other insoluble fibre, sand, and other earthy
substances and colouring matter; moreover some varieties of gum arabic
contain also a portion of what is called "bassorine," which is insoluble in
cold and hot water. These impurities necessarily interfere more or less with
the good results expected to be obtained in the various employments of gum
arabic, and the dark-coloured sorts are totally unfit for many uses.
The object of my Invention is to separate all or most of those extraneous
matters from gum arabic, and, by thus decolorising and purifying it, render it
finer, more useful, and better available for pharmaceutical, manufacturing, and
other purposes. I effect the said object by one or other of the two different
processes hereafter described. The first process is as follows:-I prepare
a rather strong solution of sulphurous acid gas, by any of the processes well
known to practical chemists, and I purify the gas previous to using it by
passing it through water contained in a suitable apparatus. The purified
acid solution of the gas must be as much as possible protected from the
contact of atmospheric air. I introduce into this solution a quantity of gum
arabic in the state imported, or in powder, in proportions varying from six to
twelve parts by weight of solution to one part of gum, according to the quality
of the latter, the strongest gums requiring a larger quantity of the solution;
however, the proportions both of the gum and of the gas in solution may be varied
if required, to suit the other circumstances of the whole process. I let the gum
dissolve in the acid solution, which process may be facilitated by the action of an
agitator in the vessel, without, however, allowing a free access of air into the latter.
When the gum is dissolved the greatest portion of its colouring matter has
been destroyed, or perhaps, to speak more properly, it has chemically combined
with the sulphurous acid, forming together a colourless compound. The
sulphurous acid may be brought into contact with the gum in other manners
than the preceding, viz., for instance, by introducing a current of the purified
gas into a solution of gum, whereby it is readily absorbed and dissolved, but

page_text: I find the first described method:more effectual for the purpose of decoloration..
Or the sulphurous acid gas may be received into a closed receiver, surrounded
with some refrigerating.substance, and there by the action of cold, and the
pressure of the gas itself, it condenses into a liquid form, and in that form may
be mixed with a solution of gum.
Now, in order to separate the acid, or the acid combined with colouring.
matter, from the gum solution, various methods may be pursued, but I prefer.
the following:-I apply heat for a short time to the close vessel containing the,
mixture, during which time the portion of gas evolved may be passed through.
a tube into another receiver containing water, and thus recovered for another
operation. I then open a stopcock placed at the bottom of the vessel, and
allow. the hot solution to run off in small portions into a larger and open
vessel containing (rather in excess) some salifiable case, which, in its com-.
bination, with sulphurous acid, forms an insoluble salt. Various substances
can be used for the purpose, but. I prefer using carbonate of baryta, as,
sulphite of baryta is an absolutely insoluble salt as well as the sulphate. The.
combination is aided by stirring, and when the whole, of the disengaged
carbonic acid gas has been driven off and the solution has become neutral, I
cover the vessel and allow it to remain in repose for some hours, so that the,
coarsest parts of the solid matters may deposit. The neutralisation, of the.
acid above described may also be effected without previously heating the liquid;
but then I recommend. to beat the mixture after the combination has taken.
place, in order to drive off all the carbonic acid which would, if allowed to
remain in the solution, dissolve a small portion of undecomposed carbonate of
baryta. After the filtration of the liquid, as herein-after described, it will be
found that all ligneous fibre, sand, and earthy. matters, and all particles of
insoluble gum, have entirely separated from the gum solution and deposited in
the vessels used, and on. the filter with the sulphite of baryta, 'very little colour.
will: have remained in the filtered solution. But, when a very white gum is,
required the process of acidulation must be repeated, and sometimes more.
than once. To that effect I introduce into the solution, previous to or after the.
filtration hereafter mentioned, a fresh portion of purified sulphurous acid gas,
in a proportion to impart to the liquid a somewhat biting sourness, and I again
neutralise. the acid with a new equivalent portion of the same base or basic,
compound employed in the first instance; all repetitions are conducted as.
herein before described till the whole of the colouring matter has disappeared.
The very, darkest sorts of gum arabic yield up their coloring matter to this
treatment. I must, however, mention that some specimens of gum arabic

page_text: abandon the whole, or nearly the whole, of their colouring matters upon the
first treatment by sulphurous acid as above described.
To effect the complete separation of the insoluble sulphite and the other
insoluble impurities from the solution operated upon, I filter it through some
very close filter, which allows no passage to any particle of solid matter. I
prefer effecting this filtration through a thin layer of pure gelatinous bydrate
of alumina laid on cloth, which may be obtained by decomposition of sul-
phate of alumina, as is well known. Or the same object may be effected
by forcing the passage of the pure liquid through unglazed earthen or stone
ware, with or without increased pressure, the said pressure produced by
exhaustion of the air from tho receiver, or otherwise. The solution comes
from the filter in a state of perfect limpidity, and then a colourless, tasteless,
and pure gum is thereby obtained, without in the least degree altering its
natural properties. I then subject the gum solution to evaporation, in order
either to bring it down to any required degree of density, or to a state of
complete dryness. The application of heat being necessary to that effect, I
recommend one of the two following modes in preference to any other,
videlicet," to expose the liquid in shallow flat-bottomed trays to a current of
heated air, purified if necessary, and at such a temperature as will not affect
the colour of the gum, and to continue the process till the liquid has been
converted into a dry thin plate; but if another form is preferred, the evaporation
may be stopped when the solution has attained the consistency of a thick
paste, when it may be shaped into lumps or drops or otherwise, and then
entirely desiccated by further evaporation. The other mode of evaporation is
in vacuum pans, without raising the temperature too high. It is advisable
to place within the paus agitators which are intended principally to break, from
time to time, the crust that forms at the surface, and which would, if suffered
to remain unbroken, prevent the freo exit of the vapour from the lower
strata. When the gum is desiccated it may be broken into pieces and extracted
from the apparatus. Another method may be adopted for separating the
sulphurous acid gas from the gum solution, without neutralising it with a
base; it is by boiling the mixture in vacuum or in the same close and air-tight
vessel, and conducting the gas into another receiver containing water; the
boiling should be continued till the whole of the gas is driven off, when it will
be found that the gum has been to a very great extent decolorised. If required
the decolorising process may be repeated by again introducing into the
vessel containing the solution a current of pure sulphurous acid gas, and
When cooled it will be
then separating it by ebullition as before stated.

page_text: found that all the impurities originally united with the gum have been
deposited at the bottom of the vessel, and the pure solution may be drawn off
either by a syphon or through a stopcock placed a little above the bottom,
or the whole contents of the vessel may be emptied into cloth bags, and therein
filtered. This method as more economical and expeditious may be better
adapted for gums intended for manufacturing purposes, for which an extreme
whiteness such as is met with only in the choicest samples of picked Turkey
gum, is not an essential requisite. The evaporation of this solution need not
be carried to complete dryness, but it may be stopped at any degree of density
that may be required for such of the arts and manufactures wherein gum
arabic is employed in a dissolved state. Both the separation of the gas
and the subsequent evaporation of the gum solution may be greatly facilitated,
and effected at a lower temperature, by connecting the vessel with an air
pump, and thereby extracting the gas or the vapour as soon as evolved, in
which case no other connection with the vessel is necessary. If the operation
has been well conducted, the temperature not having been raised too high,
and the contact with the atmospheric air completely avoided, then no trace of
acidity remains in the liquid, except that which is natural to gum arabic.
But should any slight acid reaction shew itself on testing, this can be
neutralised by the addition of an extremely minute quantity of soda or any
other suitable alkaline substance. With the exception of the process of
desiccation by heated air herein-before mentioned, I recommend for all other
operations wherein heat is employed the use of hot water or steam as the
heating medium. The vessels must be made of such materials as are not
acted upon by sulphurous acid, and it is advisable to adapt to them internal
agitators reaching the bottoms and sweeping round the gum, which is other-
wise apt to stick to the heated bottoms and burn.
The second process of decolorising and purifying gum arabic, I adopt
it as follows:-I dissolve the gum in cold or hot water in proportions
varying from six to fifteen parts by weight of water to one part of gum,
according to the different qualities of gum, and filter the solution through
cloth. I then add to it a quantity of pure gelatinous hydrate of alumina,
either alone or mixed with a little fine pipe-clay or other earthy and insoluble
substances, mixing it throughly with the solution with or without heat, so as
to form of the mixture au homogeneous compound of about the consistency of
thin paste. This is to be filtered through cloth, and the pure gum solution
that percolates is greatly decolorised, the colouring matter having been attracted
and retained by the alumina. Instead of making the mixture as above
state, the original solution of gum may be passed through a bed of alumina,

page_text: t
or alumina and other substances, and the decoloration would be equally.
effected, but then the filtration would be much slower than by the method of
previously mixing. The filtered solution must be again operated upon with.
a fresh portion. of the said pure hydrate of alumina, alone: or with other.
substances present, if a gum perfectly white is required, and sometimes: a.
second repetition of the same process may be requisite. But, as the second.
and third portions of alumina, after having served; contain very little colouring.
matter; they may serve again for the first decoloration of another portion of
gum. When the hydrate of alumina alone, or with the other substances, is.
highly charged with colouring matter, I wash it with hot water in the filter,
to separate the adbering gum from it; and this water, containing some gum.
in solution, is reserved for further dissolutions. The washed but coloured
alumina I entirely recover for new operations, by washing it with a cold,
aqueous solution, of chlorine, or with a limpid solution of chloride of lime,
filtering and again washing repeatedly with hot water. Its original whiteness
and purity are thus restored, as well as its chemical affinity for colouring
matter. The concentration of the purified gum solution, and its completo.
desiccation, if this is required, are now carried on by the same methods as
herein-before described.
After having fully described the nature of my Invention, and the several
methods by which the same is to be caried out, I declare-that-I do not confine
myself to the precise, details given, as. these may be varied without altering.
the principles. But what I claim-as-being my Invention are the following..
I claim,
First, the decoloration of all varieties of gum arabic and Senegal by sulphu-
rous. acid, by.. whatever, method the said acid be generated, in whatever
manner the said acid be brought into contact with the gum, and by
whatever means be neutralised or separated therefrom.
Second, the decoloration of all varieties of gum arabic and Senegal by
hydrate of alumina, alone, or used with other substances.
Third, the purification of gum arabic and Senegal in solution, as combined
with the process of decoloration by the means herein-before described.
Fourth, the decoloration and recovery of the hydrate of alumina, after.
having been charged with colouring matter, as herein-before described.
In witness whereof, I, the said Moses Haym Picciotto, have hereunto
set my hand and seal, this Sixteenth day of February, One thousand-
eight bundred and forty-nine."

page_text: AND BE IT REMEMBERED, that on the Sixteenth day of February, in
the year of our Lord 1849, the aforesaid Moses Haym Picciotto came before
our said Lady the Queen in Her. Chancery, and acknowledged the Specifica-
tion aforesaid, and all and every thing therein contained and specified, in form
above written. And also the Specification aforesaid was stamped according
to the tenor of the Statute made for that purpose.
Enrolled the Sorentoenth day of February in the year of our Lord One