Improvements relating to the Extraction of Gutta-percha and to Apparatus therefor.
Year: 1892

page_text: Improvements relating to the Extraction of Gutta-percha and to
Apparatus therefor.
I, DIEUDONNÉ RIGOLE, of 45 Rue St. Sébastien, Paris, in the Republic of
France, Chemist 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 relates to a process and apparatus for extracting gutta-percha
from the leaves and twigs of isonandras, dichopsis or other gutta-percha trees.
by the use of carbon disulphide.
Up to the present time gutta-percha has been extracted from isonandras,
dichopsis and other gutta-percha trees by the most natural means in default of
others, that is to say by cutting down the trees producing the same.
Experience has shown that it requires from twenty to twenty-five years for a
tree of these families to be able to supply a good yield, and that this mode of
procedure would lead sooner or later, if not to the total disappearance of these
trees, at least to their becoming very rare and would therefore augment to a
considerable extent the price of the material.
The importance of the discovery of my improved process and apparatus for
extracting gutta-percha will be obvious, because, instead of the tree being
destroyed, it obtains on the contrary, being cut in a proper manner, a greater
vitality, and every year is obtained a yield exceeding that realized in twenty
years by the method which has heretofore been practised.
In describing this improved process and the apparatus by means of which it is
carried out I will refer to the accompanying drawing.
The leaves and twigs from which the gutta-percha is to be extracted are suitably
pounded so as to uncover the cells containing the gum.
In this state they are
introduced into an exhausting vessel A.
The carbon disulphide, which I employ as a solvent in variable quantities (on ai
average from twelve to fourteen kilogrammes for the production of one kilogramme
of gutta-percha), and which is put in the boiler B, passes through the tube a in the
state of vapour into the condenser C where it condenses and then traverses the
pounded leaves and twigs. The liquid, from the disulphide containing the soluble
principles, then return to the boiler B through the tube a', the lower part of which
is provided with an automatically operating Hap & for permitting the passage of the
gum into the boiler B. Across the bore of the tube a' is placed a very fine wire.
gauze c serving as a filter or rather as a strainer..
After the disulphide has collected a certain portion of the gum, which it
conducts to the boiler B where the same is deposited, it escapes through the tube a,
in order to condense again in the space C and recommence its exhausting operation
until the gum contained in the leaves and twigs in the vessel A has been completely
extracted.
The tubes a and a' are surrounded by a sleeve of cotton, wool or any other
non-conducting material which prevents them from cooling.
In this manner the carbon disulphide which is continually being purified by the
distillation must in a short time effect the complete exhaustion of the leaves
and twigs.
Of course the carbon disulphide contained in the boiler B must never boil,
because the gum collected would otherwise become quite oxidated, which incon-
venience is obviated by placing the said boiler in a water bath D wherein water
is kept at the maximum temperature of 45 degrees centigrade.
When the exhaustion of the leaves and twigs is complete the valve c' is closed

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to prevent the communication of the boiler B with the tube a. I also close the
cock, open the cocks e, ƒ and g and introduce into the vessel A a powerful jet of
superheated steam. The steam comes from a boiler E through the tube
passes into the boiler B through the tube a². It will carry away the few globules
of gum which may still be in the leaves and twigs, traverse the tube a¹ in order
to pass to the boiler B containing the gutta-percha in solution in the carbon
disulphide, and introduce the vapours through the cock into the discharge tube i
the extremity of which dips a short distance into the water contained in the
vessel F.
The carbon disulphide, having a greater specific weight than water, falls
naturally to the bottom of the vessel F.
When the superheated steam has completely carried away the excess of carbon
disulphide into the vessel F the gutta-percha, which a few moments previously
had a sirupy appearance, becomes more and more compact as the solvent disappears
and it is then no longer a homogeneous substance which can be kneaded by hand.
In order that no disulphide shall remain in the gum the introduction of
superheated steam may be prolonged in such a manner that the gutta-percha will
not be affected by its action and that its oxidation need not be feared.
The complete operation must not occupy more than from twenty two to twenty-
five minutes for obtaining chemically pure gutta-percha.
Other solvents than carbon disulphide would give similar results, such as benzene,
chloroform and the like, but the price of these substances which I have tried
augments the cost price of the gutta-percha so much that their employment is
not practicable for commercial purposes.
It may be observed that if use is made of benzene as a solvent the gum
collected will contain some traces of this substance, the elimination of which
presents almost insuperable difficulties.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what I
claim is :-
First. A process for extracting gutta-percha from the leaves and twigs of
isonandras, disopchis or other gutta percha trees by the employment of carbon
disulphide, which consists in establishing a continuous circulation of the condensed
vapours from the dissolving liquids through the materials to be treated and
through a boiler maintaining the solvent at a temperature of about 45 degrees
centigrade, this circulation being followed by an injection of steam for the purpose
of carrying away the solvent to the exterior and leaving the gutta percha in a
pasty state in the boiler substantially as hereinbefore described.
Second. For carrying into practice the process specified in the first claim, the
employment of an apparatus comprising a boiler B for receiving carbon disulphide
and heated by a water bath, a vessel A for containing the leaves and twigs to be
treated, a steam boiler E and a vessel F, the said boiler B and vessel A being
connected by the pipes a and a', in order to establish a continuous current o
disulphide through the material to be treated and cause the dissolution of the
gutta-percha, the generator E being connected with the boiler B through the
pipes and a and the vessel A in order that this steam, when the dissolution of
the gutta-percha is effected, shall carry away the globules which may remain in
the vessel A. and remove the dissolving liquid for carrying it away into the vessel F
through the pipe for the purpose of leaving the extracted gutta-percha in a pasty
state in the boiler B, this apparatus being arranged and operating substantially as
and for the purposes described with reference to the accompanying drawing,
Dated this 3rd day of March 1892.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.