IMPROVEMENTS IN PURIFYING WOOD AND OTHER VINEGAR
Year: 1862

page_text: LETTERS PATENT to Hermann Eschwege, of 14, Mincing Lane, in the
City of London, for the Invention of "IMPROVEMENTS IN PURIFYING WOOD
AND OTHER VINEGAR."
Sealed the 6th January 1863, and dated the 9th July 1862.
PROVISIONAL SPECIFICATION left by the said Hermann Eschwege at
the Office of the Commissioners of Patents, with his Petition, on the
9th July 1862.
I, HERMANN ESCHWEGE, of 14, Mincing Lane, in the City of London, do
hereby declare the nature of the Invention for "IMPROVEMENTS IN PURIFYING
WOOD AND OTHER VINEGAR," to be as follows:-
This Invention has for its object improvements in purifying wood and other
vinegar. For these purposes the wood or other vinegar is to be diluted with
water, and then subjected to the action of a succession of filters composed of
wood or other charcoal, the process of filtration being carried on in such
manner that each succeeding filterer into which the diluted vinegar is conducted
shall be in a more pure or uncontaminated state than that through which the
diluted vinegar bas last passed. In order to accomplish this, a series of filters
is so arranged that each filter, of the series is to be capable of being coupled
with the vat or vessel from which the supply of unfiltered diluted vinegar is kept,
and all the filters. of the series are to be capable of being coupled up in such
manner, that the diluted vinegar having passed one filter, it may pass into the

page_text: next, and the next, and so on to the filter which, for the time being, is the last in
the series. By preference, the top of each filter of the series is, when at work,
connected with the bottom of the filter, which is for the time the next to it in
the series, and the connections of the filters are to be so arranged, that when
any one of the series has been for a time the last in the series, and the diluted
vinegar is found to be coming off less pure than is desired from such last filter,
it may become the last but one filter in the series by being coupled to a clean
filter, which for a time is to be the last in the series, and the vat or vessel is at
the same time to be disconnected from the filter which has been previously
acting as the first filter in the series, and is to be connected with the filter
which has been previously for a time acting as the second filter of the series,
and in this manner is the first filter of the series to be removed out of the
series when a fresh or clean filter is introduced as the last of the series. The
diluted filtered and purified vinegar is then to be subjected to heat, in order to
evaporate the water therefrom, and to increase the strength to the extent
desired.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Hermann Eschwege, in the Great-Seal Patent Office on the
9th January 1863.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HERMANN
ESCHWEGE, of 14, Mincing Lane, in the City of London, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by' Her Letters
Patent, bearing date the Ninth day of July, in the year of our Lord
One thousand eight hundred and sixty-two, in the twenty-sixth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Hermann Eschwege, Her special licence that I, the said Hermann
Eschwege, my executors, administrators, and assigns, or such others as I, the
said Hermann Eschwege, my executors, administrators, and assigns, should
at any time agree with, and no. others, from time to time and at all times
thereafter during the term therein expressed, should and lawfully might
'make, use, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN PURIFYING WOOD AND OTHER VINEGAR," upon the condition
(amongst others) that I, the said Hermann Eschwege, my. executors or
administrators, by an instrument in writing under my, or their, or one of
their hands and seals, should particularly describe and ascertain the nature

page_text: of the said Invention, and in what manner the same was to be performed,
and cause the same to be filed. in the Great Seal. Patent. Office within
six calendar months next and immediately after the date of the said Letters
Patent.
7 I
NOW KNOW YE, that I, the said Hermann Eschwege, do hereby declare
the nature of the said .Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement thereof, that is to say:
This Invention has for its object improvements in purifying wood and other
vinegar. I have ascertained that well-burnt charcoal has a most beneficial
effect, when used in a series of filters, as herein explained, in purifying acetic
acid (whether obtained by destructive distillation, or by fermentation, or from
impure alcohols) if the affinity of the acid for certain impurities is first
destroyed by largely diluting the acid when in the acid state with water or or
with a smaller dilution when the acid is neutralized; I therefore either largely,
dilute with water wood (pyroligneous) acid or other acid, and then subject
this mixture to the action of a series of charcoal filters, or I neutralize the
acid, and subject the neutralized acid diluted with water to the action of a
series of charcoal filters. The filtration is conducted in such a manner that each
successive filter of the series shall effect the filtration of a purer and purer
liquid, and when it is ascertained that the filtered liquid coming away from
the last filter of the series is not any longer sufficiently pure, a fresh filter is
to be introduced and made the last filter of the series, while the first filter of
the series is to be removed, and the supply of the liquid is to be introduced
into what was previously the second filter of the series, and so on continuously.
as the filters require to be changed. The filtered liquid is afterwards,
according to desire, easily converted by ordinary known means into the acetate
or acetic acid of desired strength.
Having thus stated the nature of my Invention, I will now proceed to
describe more fully the manner of performing the same, and in so doing, I
will speak chiefly, of the purification of pyroligneous acid, this being the more
important and difficult one to deal with.
f..
I take crude pyroligneous acid, from which, by preference; I first expel the
naptha by distillation, dilute it then with from three to four times or more,
if necessary, its bulk of water (and have it, in preference, well cleared of its,
tarry matters,) and I afterwards filter the mixture through a succession of.
charcoal filters, by preference composed of wood charcoal, or I neutralize the
crude pyroligneous acid (by preference with lime or soda), and filter a diluted.
mixture thereof containing from 10 to 20 % of neutralized acid or acetate.
°

page_text: through a succession of charcoal filters composed, by preference, of animal
charcoal. The naptha may in each case be left with the acid and filtered with
it, and be afterwards expelled, but I think it preferable, and leading to better
results, to remove the naptha first. Neutralized wood acid or dry acetate
of lime, as it occurs largely in commerce, is purified in the same manner
(first diluting it to 10 to 20 %) by filtering the diluted mixture through a
succession of filters composed of animal charcoal.
It should be remarked, in regard to the dilution of the wood or other acids
used, that the proportion of water with which the acid is best diluted varies
in some degree according to its nature and purity, but I find a dilution down
to about 2% of acetic acid in the mixture usually most beneficial, whilst
with a neutralized acid or acetate I find 10 to 20% of acetate or the cor-
responding proportion of acetic acid in the mixture the best for the purpose.
The diluted mixture is allowed to stand 24 hours before being filtered. It
should be stated that the construction, dimensions, and numbers of the filters
may be varied, but the following is the arrangement I recommend for a
regular daily purification of 2000 gallons computed at a strength of 5° of
acetic acid in the acid state. I prefer to use for this purpose a series of
fifteen filters made of a cylindrical form of about 9 feet in height and 2 feet
in diameter all connected together so as to form a succession, and provided
with the necessary air cocks. In each filter, at a few inches above the
bottom and also at a few inches below the top is a perforated plate, and it is
between these perforated plates that the charcoal is placed in order to form
the filter. The charcoal should be well burnt and broken into pieces about
the size of peas. I give the preference to charcoal made from light woods
such as alder, willow, pine, birch, &c; provision should be made for connecting
each of the filters of a series with the vat or vessel in which the diluted acid
about to be filtered is contained, and it is preferred that the arrangements of
apparatus used should be such that the diluted acid should flow from the
vessel containing it into the bottom and below the false bottom of the filter,
which for the time being is the first and least clean of the series of filters. It
is also preferred that provision should be made for the diluted acid as it
passes out from the upper end of the first or other filter in the series to flow
into the bottom of the next filter in the series, and so on from filter to filter
till the diluted acid passes out of the filter which for the time is the last of the
series, So soon as it is found that the diluted acid coming away from the
filter, which for the time being is the last filter of the series, is less than.
is desired, the first filter of the series is to be removed, and a fresh or clean.
filter is to be introduced into the series after the filter which was previously
pure

page_text: the last filter in the series. The supply vessel is to be connected with the
filter which was previously the second filter in the series, and the process is to
go on till the diluted acid is again found to be coming away from the newly-
introduced and now last filter in the series less pure than is desired when the
filter which has been acting as the first of the series is to be disconnected, and
another fresh or clean filter is to be introduced into the series, and is to form
the last filter of the series, and so on continuously, whereby the diluted acid
will be at all times successively subjected to the action of cleaner and cleaner
charcoal as it passes from filter to filter from the time it leaves the supply vat
or vessel till it comes away from the filter which for the time being is the last
of the series. And I recommend for a regular daily purification of 2000
gallons acetic acid in its neutralized and diluted state (these 2000 gallons
computed at 10% of acetic acid or the corresponding proportion of acetate)
the use of ten such filters composed of well-burnt granulated animal charcoal.
I would generally remark, that I recommend that the filtration of vinegar in
its acid state should be through filters composed of wood charcoal whilst
neutralized acid and acetates should be through filters composed of animal
charcoal.
I do not limit myself to any particular degree of dilution, or to any specific
number of filters, but I claim the purification of vinegar (acetic acid) in its
acid or neutralized state by filtering the same in a diluted state, as described,
through a series of charcoal filters, adding a fresh filter at the end, and dis-
connecting the first and foulest filter of the series, as explained.
: In. witness whereof, I, the said Hermann Eschwege, have hereunto set.
my hand and seal, this Eighth day of January, in the year of our
Lord One thousand eight hundred and sixty-three.
HERMANN ESCHWEGE.
(L.S.)