Process for the Production of Glue and Gelatine from Bones.
Year: 1894

page_text: Date of Application, 1st Feb., 1894-Accepted, 3rd Mar., 1894
COMPLETE SPECIFICATION.
Process for the Production of Glue and Gelatine from Bones.
We JULIUS GRILLO of Neumühl-Hamborn in the German Empire, Manu-
facturer, and Dr. MAX SCHROEDER of Düsseldorf in the German Empire, 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 :-
The production or manufacture of glue from ordinary bone material has hitherto
been carried out in two different ways. Either the bones are decomposed direct
according to the so called steaming process, by means of high pressure steam
into glue liquid and residual phosphate, or the extraction process is employed.
according to which the phosphate is first extracted by watery acids, especially
muriatic acid and sulphurous acid, and then the pure residual cartilage boiled down
into glue. As in the first named process, steam pressures of from two to three
atmospheres with the corresponding temperatures of 130° to 140° Celsius are
required, and which at once bring about a strong decomposition of the glue
substance, there is obtained only a dark low value glue. Much better is the glue
produced by the second process because the extracted cartilage may readily
be boiled down to glue liquid at temperatures of 100° Celsius and under, but the
performance of this process is somewhat costly in consequence of the great
expenditure of acid and the requisite preparation of the lyes.
The process of this invention differs even in principle from the two processes
above referred to. It is based on the dry opening out or disintegration of the
bones, without dissolving the phosphates-by means of gaseous sulphurous acid.
Hitherto it has not been known that bones containing little moisture have quite
a peculiar capacity for the absorption of gaseous sulphurous acid. If, at the ordinary
temperature a current of sulphurous acid be conducted through air dried or slightly
moistened bones placed in a closed vessel, it will be found that the sulphurous acid
passing out at the top of the vessel does not correspond in quantity to that
introduced at the bottoin part of the vessel. At the beginning, the SO,, is almost
wholly absorbed; later the absorption proceeds more slowly so that a portion of
the sulphurous escapes at top. After 12 hours, the bones, with the exception
of those of the very hard tubular kind, will have absorbed sulphurous acid to the
extent of from 10 to 12 per rent. of their weight. If the current of sulphurous acid
be continued, still more and more of it will be taken up by the bones, and it may
without difficulty rise to 15 and even 20 per cent. of the weight of the bones. If the
bones be then removed from the closed vessel and exposed for a length of time to
the air it will be found that they give off sulphurous acid but only until
the contents of SO₂, have fallen to the analytic average contents of about from
11 to 12 per cent.
These contents of SO, remain constant even when the bones have been
exposed for months, and the SO, is not expelled by warmth, by water, or by a
current of steam.
From these observations it may be deduced that by the absorption of from
11 to 12 per cent. of SO2, the point of saturation of a determined chemical affinity
has been reached. That quantity of SO, which had been absorbed above this
per centage having been held temporarily either by the capacity for condensation
possessed by porous bodies or by a slight chemical binding.
As a chemical binding of the sulphurous acid by the cartilage substance of the
bones is excluded, therefore the said considerable absorption of SO₂ can only be

page_text: It is known that
on an average bones consist of one third of organic and two thirds of inorganic
substance, the latter-irrespective of the small carbonate contents-consisting mainly
of phosphate of lime, If now the absorption of from 11 to 12 per cent. of sulphurous
acid be attributed to the inorganic portion alone of the bones there results an
absorption by the same of from 16 to 17 per cent. of SO2. The conversion of the
bone phosphate would therefore proceed substantially in accordance with the
following equation which presupposes an absorption of 16.3 per cent. of SO, :—
(PO) Ca, + SO2 + H2O - 2 POHCa + CaSO3.
attained by a thorough conversion of the phosphates of the bones.
To this acceptation also corresponds the circumstance that the phosphate has
passed over into the citrate soluble form.
Whether upon this conversion there is further an absorption of water of
crystallisation is of hardly any importance from a commercial stand point. The
usual amount of moisture in the bones is as a rule sufficient for the water require-
ments of the conversion and if this should not be the case it might easily be increased
by a previous addition of moisture thereto.
Bones thoroughly dried at a temperature of 100° Celsius possess only a small
capacity for taking up SO2, because they are deficient in the water requisite in the
aforesaid conversion.
Instead of the pure gaseous SO2, mixtures of SO2 with nitrogen, oxygen,
carbonic acid and other neutral gases may be employed but with a high degree of
dilution the conversion of the phosphate of the bones is rendered slower; on the
other hand by the employment of a high gas pressure with corresponding
concentration of the active gas molecules the conversion may be not inconsiderably
accellerated.
The process of the invention would have hardly any commercial importance if it
By
were not accompanied by a penetrating change in the structure of the bones.
the conversion of the phosphate the thinner previously elastic bones are rendered
quite brittle and may be broken to pieces without much difficulty. In consequence
of their porous structure they oppose only a slight resistance to the boiling water
and at 100° Celsius and under boiled down to glue nearly as quickly as the pure
extracted cartilage. The sulphite-phosphate of the porous bone parts-falls
completely to powder after only two hours boiling; closer or more solid parts are
then so soft that they may be compressed with the fingers; only the inner parts
of hard tubular bones which are not sufficiently acted upon by SO2, preserve
their structure.
The glue liquid thus obtained is of a bright colour but owing to the simple acid
phosphate, somewhat milky. It also contains salts in solution and reacts strongly
acid. It is therefore not suitable for immediate working into glue. The salts
resulting from the conversion process, the phosphate CaHPO, and the neutral
sulphite, are indeed insoluble in water but as in practice a sinall excess of SO, by
reason of the condensing action of the bones is not to be avoided, there will be found
small quantities of acid or bisulphite and monobasic phosphate CaH (PO) in the
solution. These salts upon the drying of the glue would be separated and render
the glue quite opaque.
The removal of these disadvantages may be accomplished in a simple way by
neutralising the glue liquid with milk of lime. By this means not only is the acid
reaction suppressed but the whole of the salts except a small uninjurious residue, sink
down in an easily filtered form carrying with them also all other impurities so that
there results a perfectly clear neutral glue solution mostly of a bright yellow colour,
which solution may be worked up into glue in a known way.
The process is carried out commercially in the following manner :-
The previous
The bones to be treated may have had their fat removed or not.
extraction of the fat is however so far advantageous that many odorous stuffs are
removed at the same time, and the pores of the bones are set freer for the reception
of the SO. The previous reduction of the bones to small pieces by mechanical
means is of course useful for accellerating the absorption and conversion.

page_text: For the operation of opening out the bones by means of gaseous sulphurous acid
large air tight vats of wood, chests lined with lead, or iron cylinders are suitable.
The process may also be carried on continuously in shaft like apparatus charged at
top and from time to time partially discharged at bottom.
With dilute SO2 gases, it is preferable to use a large number of apparatus
connected together by pipes so as to form a battery. The sulphurous acid is
conducted through the whole row passing through the several apparatus from
underneath upwards. When the bone material in the first of the apparatus has
absorbed from 10 to 12 per cent. of SO2, this apparatus is shut out of the set for a
length of time so that the quantity of SO, which preliminarily is only held fixed
by condensation, may enter into chemical combination with the inner bone parts.
remaining still unsaturated. If the installation consists of eight apparatus, four of
these may always be in use for the absorption of the sulphurous acid, three in a
state of rest after the absorption process and one in course of being charged or
discharged. After shutting out apparatus 1, apparatus 5 with fresh boue material
is connected again. The SO, gases then pass through the apparatus 2, 3, 4, 5, in
succession whilst 7, 8, 1, are in a state of rest. Apparatus 6 which has been
standing longest is then emptied, charged with fresh bones, and in place of
apparatus 2 to be shut out, connected in the set so as at once to be in the continuous
round upon the contrary current principle.
If the size of the several apparatus be such that each will represent one day's
output the round would always be ended in eight days, four of these serving for the
absorption, three for rest for the purpose of the chemical combination of the
superficially condensed SO, and one day for discharging and charging. This
battery apparatus is especially adapted for places where no pure SO gases but
gaseous mixtures of SO2 and neutral gases such as the gases of combustion of
sulphur or the furnace gases from pyrites, are used.
If compressed liquid SO, is to be had the operation may be carried out very
simply under pressure in separate iron cylinders, in which case for each 100 cwts.
of bones from 10 to 12 cwts. of liquid SO2 is passed into the apparatus and this
latter left to wait until the combination of the SO2 has taken place according to
rule. The small quantity of carbonic acid evolved from the bones is when the
pressure becomes too high to be discharged from time to time through a valve.
Upon completion of the conversion the bone mass is subjected to a vacuum in order
to remove as far as possible the free SO, still present which would be disagreeable.
when the apparatus is being emptied.
Instead of the compressed liquid anhydrous SO2, the corresponding quantity of.
pure SO₂ may be forced into the apparatus by means of a compressor. For every.
100 lbs. of bones two and a half or rather more cubic yards of pure SO, gas would
be required, which quantity is capable of exact measurement by the number of
revolutions of the compressor.
After removal from the absorption apparatus the bones are soaked in water for
two or three days to remove soluble salts and especially also the odorous and
colouring stuff's made soluble by the SO2.
The boiling down of the bones to glue is now proceeded with. As iron vessels
cannot well be employed owing to the acid properties of the glue liquid, wood rats
or lead lined vessels are used. They are charged with the bone material and then
with sufficient water to cover the latter. The heating up to 100° Celsius is
effected by means of steam worms or by the direct introduction of steam at the
bottom of the vessel. As, after two or three hours boiling the larger quantity of
the glue substance is dissolved, it is best then to withdraw this first liquid in order
that the glue may not be decomposed by boiling too long. Fresh water is then
added to the remaining glue substance and boiled to form a thinner liquid which
may be added to the other in special clarifying vats. By a third boiling a final
quite thin solution is obtained which is utilised by placing it with the next quantity
of bones.
When bones that have not had their fat extracted are used for the operation,

page_text: the separation of the fat from the glue liquid must be effected in the clarifying vats
where it rises to the surface. With bones from which the fat has been previously
extracted this manipulation is of course unnecessary.
The still hot glue liquid is now neutralised with milk of lime to remove the
dissolved phosphates and sulphites, the glue liquid being at the same time stirred.
The milk of lime used for this purpose may contain about 10 parts of caustic lime
to 100 parts of water. Instead of the lime the other alkaline earths-baryta,
strontia, hydrate of magnesia-may be used, or with a less good result, their
carbonates. It is not advisable to use the alkalies proper or ammonia because they
form soluble salts in the glue liquid which salts would in the drying of the glue
cakes separate in the form of turbidness.
After the neutralisation, the glue liquid is allowed to stand for some time
whereupon the separated stuffs are thoroughly precipitated. The clear bright
yellow glue solution may be drawn off, or separted from the precipitate by the aid
of a filter press.
The further working of the glue liquid into cakes is effected in a known way by
evaporating in open pans or in vacuum pans, pouring into moulds, cooling, cutting
aud drying.
By the treatment of fresh bright bones according to this process a nearly
colourless and odourless gelatine is obtained.
The yield of glue is good. It amounts to from 16 to 24 per cent. according to
the quality of the bone material used.
The residue of the bones consisting of a mixture of phosphate CaHPO, and
monosulphite of lime remaining behind after the boiling process is dried and
ground to powder under a light pressure. The inner, unconverted and still hard
pieces of the tubular bones preserve their structure and may be separated from
the powder by sifting. Probably owing to deficiency of moisture the innermost
parts of the hard bones had only absorbed from 3 to 4 per cent. of SO, to
treatment with which they may be again subjected, but as they only amount to
10 per cent. of the bones used and do not contain much glue substance this further
treatment with SO, might without great loss be abstained from more especially as
the nitrogen of the same has a certain value as manure.
The ground residue is not suitable for direct application as manure owing to its
contents of sulphite. The powder is therefore treated with sulphuric acid in closed
cylinders with application of stirring mechanism in order with the formation of
superphosphate to remove the sulphurous acid in gas form. The eliminated SO, is
again utilised by its introduction into the absorption apparatus for the treatment of
further quantities of bones.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is :
1. The process for the production of glue and gelatine from bones by the dry
disintegration of the structure of the same by means of sulphurous acid either
alone or diluted with other gases, substantially as described.
2. The treatment of air dried or moistened bones with sulphurous acid in closed
apparatus for the purpose of the chemical absorption, of said acid with separation
of the tribasic phosphate of the bones mainly into compounds insoluble in water
and which in their composition correspond substantially to a mixture of the
phosphate CaHPO, and neutral sulphite CaSO3, substantially as described.
3. The analysis of the bones treated in the manner referred to and the structure
of which is relaxed by the chemical conversion, by means of steam or boiling
water, into a glue liquid containing an acid some bisulphite CaH2(SO) and
phosphate CaH (PO); and a residue composed substantially of calcium
phosphate CaHPO, and neutral calcium sulphite CaSO, in conjunction with
undissolved organic stuffs, substantially as described.
4. The neutralisation of the glue liquid obtained in the manner referred to, by

page_text: means of milk of lime, or baryta, strontia, hydrate of magnesia or the carbonates
of the same, for the purpose of separating and removing the dissolved acid lime
salts, substantially as described.
Dated this 1st day of February 1894.
CAPITAINE & VON HERTLING,
89, Chancery Lane, London, W.C., Agents for the Applicants.