IMPROVEMENTS IN THE PROCESS OF PRODUCING TANNIN WHEREBY THE MINOR PRODUCTS, SUCH AS CELLULOSE, "A com- ARE OBTAINED. GUM, ACETIC ACID, AND BI-SULPHITE OF LIME muni
Year: 1882

page_text: LETTERS PATENT to Edwin Ambrose Brydges of the firm of Brydges & Co.,
Engineers & Patent Solicitors of 73 Königgrätzer Str. in the City of Berlin
and German Empire and of 6 St. Leonard's Terrace Upton in the County
of Middlesex, for an invention of "IMPROVEMENTS IN THE PROCESS OF
PRODUCING TANNIN WHEREBY THE MINOR PRODUCTS, SUCH AS CELLULOSE,
"A com-
ARE OBTAINED.
GUM, ACETIC ACID, AND BI-SULPHITE OF LIME
munication by A. Mitscherlich, of the town of Münden, in the German
Empire aforesaid.
PROVISIONAL SPECIFICATION left by the said Edwin Ambrose Brydges
at the Office of the Commissioners of Patents on the 6th April 1882.
EDWIN AMBROSE BRYDGES of the firm of Brydges & Co Engineers and Patent
Solicitors of 73 Königgrätzer Str. in the City of Berlin and German Empire and
IMPROVEMENTS IN
of 6 St. Leonard's Terrace Upton in the County of Middlesex.
THE PROCESS OF PRODUCING TANNIN, WHEREBY THE MINOR PRODUCTS SUCH AS
CELLULOSE, GUM, ACETIC ACID AND BI-SULPHITE OF LIME ARE OBTAINED. [A
the German
communication by A. Mitscherlich, of the town of Münden, in
Empire aforesaid].
The process consists principally in the action of the so termed bi-sulphite of
lime (sulphite of lime dissolved in a weak solution of sulphurous acid) on previously
steamed portions of plants or small pieces of wood, the water having a temperature
above the boiling point.
I give below only a description of the process when wood is employed, the
process for other vegetable matters will be clear from the same.
The weak solution of bi-sulphite of lime is produced in the following manner:
Small pieces of carbonate of lime are placed in a tower, and from above a stream of
water, while at the same time from below a stream of sulphurous acid (SO) is
directed upon them..
This sulphurous acid is partly obtained by the combustion of sulphur or sulphides
and is partly from the residues obtained by boiling down the fluid produced in the
process described below.

page_text: Other sulphites, for instance sulphite of soda and such like can be prepared
in a similar manner at a very small cost, which said sulphites can under certain
circumstances also be employed in my said process.
Wood which is deprived of its bark and not sawn up very small (with or without
the branches) is placed in a suitable boiler or receiver which said boiler is completely
lined with bricks, cement and lead and is further provided with heating tubes
and the minor appurtenances for the supply and escape of fluid, steam and
So on.
After the boiler is closed the wood is steamed and the aforesaid solution of
bi-sulphite of lime admitted.
The duration of this process varies according to the size of the wood; the
average duration being upwards of 8 hours at a temperature exceeding 110° C.
Under this action those parts of the wood surrounding and penetrating the
cells of the same dissolve, whereas the cells themselves remain in the fluid as a soft
mass.
The contents of the boiler are now heated to boiling point and the heat
maintained so long as the vapors which are conducted into the carbonate of lime
contained in the above named tower smell strongly of sulphurous acid.
Instead of conducting the sulphurous acid into the tower it can be conducted
into a box or receptacle containing water and freshly slaked lime stirred together.
By this means a pure concentrated solution of bi-sulphite of lime is produced, which
finds a constantly increasing application in fermentation processes for preventing
the formation of acetic acid and substances opposed to decomposition.
If instead of slaked lime carbonate of soda or a similar salt is introduced into the
box or receptacle, the various sulphites can easily be produced.
The fluid which is now separated from the cellular matter and which contains
besides salts of lime (sulphate of lime etc) tannin gum, acetic acid and a small
residue of sulphurous acid SO,, is employed principally:-
a) as material for tanning hides.
b) for the manufacture of gum.
c) for obtaining vinegar.
a) The lime is separated in the simplest manner from the fluid by means of
sulphuric acid SO..
The fluid can then be used at once for tanning hides or if the said fluid is to be
exported after being concentrated. This concentrated fluid is diluted before being
employed for tanning purposes.
The other substances contained in the fluids do not as a rule have any
deteriating influence on the tanning.
The tannic acid can also be precipitated from the solution by milk of lime and
can after a considerable time be again separated from the dried precipitate by means
of acids.
I have observed that the small quantity of sulphurous acid contained in
the fluid causes a swelling of the hides during the process of tanning accelerates
the same and also increases the durability of the substances placed in the
solution.
In this process the tannin in the solution at first obtained shews the same
peculiarity as the tannin of the bark belonging to the wood, for instance, the
solution prepared from the wood of the fir-tree alters the natural color of the hide
and that of the bark only to a small degree.
: The coloring effect of the tannic acid is however under certain circumstances
altered by the last named operation.
b) In order to manufacture gum or adhesive substances, the solution alone is
evaporated and the crystallized sulphate of lime separated by decantation.
The somewhat brown residue which when exposed to the air attracts moisture
to a great degree can be, in many cases, used in place of the ordinary gum
arabic.
The gum when evaporated to dryness and also the concentrated solution of the
J

page_text: same lasts for years in an entirely unaltered condition, no sign of rot or decay
occurring.
For some uses, it is advisable to precipitate the lime from the solution by means
of sulphuric acid, or in other manner, and to boil the separated sulphurous acid out,
or instead of the last named operations to transform the sulphurous acid into
sulphuric acid by adding chlorate of potash.
It is also necessary for many purposes to extract the tannic acid from the
solution before using the gum.
The acetic acid is obtained by condensing the vapors arising during the
concentration of the fluid.
Alcohol can be produced by fermenting a portion of the fluid obtained.
The insoluble residue in the boiler is cellulose with portions of the twigs of the
wood which latter on account of their compact form are not altered materially
in the boiler and can easily be separated mechanically with the bark.
Entirely white or nearly white cellulose is obtained by this process in a much
larger quantity than has hitherto been considered to be in the wood-for instance
from air dry pine I obtain 66% of air dry cellulose.
This said cellulose can be used at once, or after being bleached with chloride of
lime, in the manufacture of paper and even in some cases for making fabrics.
ADVANTAGES 'IN COMPARISON WITH KNOWN PROCESSES:―
The solution in its action upon the wood does not require the same to be cut up
in such small portions and, such a low temperature and pressure being employed,
the boiler in consequence of its covering undergoes hardly any strain and the
danger of an explosion does not exist.
The steam process assists in an important degree the after reaction of the
bi-sulphite of lime, in consequence of which it is sufficient to treat the wood once
with the solution.
The quantity of cellulose obtained is very large.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Edwin Ambrose Brydges in the Great Seal Patent Office on the
6th October 1882.
EDWIN AMBROSE BRYDGES of the firm of "Brydges & Co" Engineers & Patent
Solicitors of 73 Königgrätzer Strasse in the City of Berlin and German Empire.
and of 6 St. Leonards.Terrace Upton in the County of Middlesex IMPROVEMENTS
IN THE PROCESS OF PRODUCING TANNIN WHEREBY THE MINOR PRODUCTS SUCH AS
CELLULOSE, GUM, ACETIC ACID AND BI-SULPHITE OF LIME ARE OBTAINED, A
communication by A. Mitscherlich of the Town of Münden in the German Empire
aforesaid.
The process consists principally in the action of the so termed bi-sulphite of
lime (sulphite of lime dissolved in a weak solution of sulphurous acid) on previously
steamed portions of plants or small pieces of wood the water having a temperature
above the boiling point.
I give below only a description of the process when wood is employed, the
process for other vegetable matters will be clear from the same.
The weak solution of bi-sulphite of lime is produced in the following manner :-
Small pieces of carbonate of lime are placed in a tower and from above a stream
of water, while at the same time from below a stream of sulphurous acid (SO3) is
directed upon them.
The sulphurous acid is partly obtained by the combustion of sulphur or sulphides
and is partly from the residues obtained by boiling down the fluid produced in the
process described below. Other sulphites, for instance sulphite of soda and such
like can be prepared in a similar manner at a very small cost, which said sulphites
can under certain circumstances also be employed in my said process..
Wood which is deprived of its bark and not sawn up very small (with or
without the branches) is placed in a suitable boiler or receiver which said boiler
is completely lined with bricks cement and lead and is further provided with
heating tubes and the minor appurtenances for the supply and escape of fluid,
steam and so on.
After the boiler is closed the wood is steamed and the aforesaid solution of
bi-sulphite of lime admitted.
The duration of this procèss varies according to the size of the wood; the
average duration being upwards of 8 hours at a temperature exceeding 110° C.
Under this action those parts of the wood surrounding and penetrating the cells of
the same dissolve whereas the cells themselves remain in the fluid as a soft mass.
The contents of the boiler are now heated to boiling point, and the heat maintained
so long as the vapors which are conducted into the carbonate of limè contained
in the above named tower smell strongly of sulphurous acid.
Instead of conducting the sulphurous acid into the tower it can be conducted
into a box or receptacle containing water and freshly slaked lime, stirred together.
By this means a pure concentrated solution of bi-sulphite of lime is produced,
which finds a constantly increasing application in fermentation processes for
preventing the formation of acetic acid and substances opposed to decomposition.
If instead of slaked lime, carbonate of soda or a similar salt is introduced into
the box or receptacle the various sulphites can easily be produced.
The fluid, which is now separated from the cellular matter and which contains,
besides salts of lime (sulphate of lime etc.) tannin, gum, acetic acid and a small
residue of sulphurous acid (SO), is employed principally:
a,) as material for tanning hides.
b) for the manufacture of gum or adhesive substances.
c.) for obtaining vinegar.

page_text: a) The lime is separated in the simplest manner from the fluid by means of
sulphuric acid SO, The fluid can then be used at once for tanning hides or if the
said fluid is to be exported after being concentrated. This concentrated fluid is
diluted before being employed for tanning purposes. The other substances
contained in the fluids do not as a rule have any deteriating influence on the
tanning. The tannic acid can also be precipitated from the solution by milk of
lime and can after a considerable time be again separated from the dried precipitate
by means of acids.
I have observed that the small quantity of sulphurous acid contained in the
fluid causes a swelling of the hides during the process of tanning, accelerates the
same and also increases the durability of the substances placed in the solution.
In this process the tannin in the solution at first obtained shews the same
peculiarity as the tannin of the bark belonging to the wood; for instance the
solution prepared from the wood of the firtree alters the natural color of the hide
and that of the bark only to a small degree. The colouring effect of the tannic
acid is however under certain circumstances altered by the last named operation. .
b) In order to manufacture gum or adhesive substances, the solution alone is
evaporated and the crystallized sulphate of lime separated by decantation.
The somewhat brown residue which when exposed to the air attracts moisture
to a great degree can be in many cases used in place of the ordinary gum arabic.
The gum when evaporated to dryness and also the concentrated solution of
the same lasts for years in an entirely unaltered condition no sign of rot or decay
occuring.
For some uses it is advisable to precipitate the lime from the solution by means
of sulphuric acid or in other manner and to boil the separated sulphurous acid out,
or instead of the last named operations to transform the sulphurous acid into
sulphuric acid by adding chlorate of potash.
It is also necessary for many purposes to extract the tannic acid from the
solution before using the gum.
The acetic acid is obtained by condensing the vapors arising during the
concentration of the fluid.
Alcohol can be produced by fermenting a portion of the fluid obtained.
The insoluble residue in the boiler is cellulose with portions of the twigs of the
wood which latter on account of their compact form are not altered materially in
the boiler and can easily be separated mechanically with the bark.
Entirely white or nearly white cellulose is obtained by this process in a much
larger quantity than has hitherto been considered to be in the wood-for instance
from air dry pine I obtain 66° of air dry cellulose.
This said cellulose can be used at once or after being bleached with chloride of
lime, in the manufacture of paper and even in some cases for making fabrics.
ADVANTAGES IN COMPARISON WITH KNOWN PROCESSES :—
The solution in its action upon the wood does not require the same to be cut
up in such small portions; and, such a low temperature and pressure being
employed, the boiler in consequence of its covering undergoes hardly any strain
and the danger of an explosion does not exist.
The steam process assists in an important degree the after reaction of the
bisulphate of lime in consequence of which it is sufficient to treat the wood once
with the solution.
The quantity of cellulose obtained is very large.
Having now described my said Invention and the manner in which the same
is to be carried into effect I claim and desire to have secured by Letters Patent.
1. The preparation of tannin, adhesive substances and fermentable fluid by
treating the wood with a solution of the corresponding salt of lime at a tempe-
rature above 108° C and at the same time obtaining as subproducts cellulose and
acetic acid substantially as described in the foregoing specification.

page_text: 2. The preparation of the solution of the so termed bi sulphite of lime and the
reapplication of the expelled sulphurous acid substantially as described in the
foregoing specification.
3. The direct employment of the fluid containing the sulphuric acid or the
steamed mass or the decomposed lime impregnated with tannic acid as tanning
material substantially as described in the foregoing specification.
In Witness whereof I-the said Edwin Ambrose Brydges have hereunto set
my hand and seal this 28th day of September in the year of our Lord
One thousand eight hundred and eighty two.
Witnesses:
JOHN
TONKIN.
ANTHONY STEFFEN.
EDWIN A. BRYDGES (L.S.)