AN IMPROVED PROCESS OF BLEACHING PAPER PULP, TEXTILE FABRICS, AND OTHER SUBSTANCES OR MATTERS
Year: 1855

page_text: LETTERS PATENT to Paul Firmin Didot, Chemist, of Paris, in the French
Empire, for the Invention of "AN IMPROVED PROCESS OF BLEACHING PAPER
PULP, TEXTILE FABRICS, AND OTHER SUBSTANCES OR MATTERS."
Sealed the 80th October 1855, and dated the 21st May 1855.
PROVISIONAL SPECIFICATION left by the said Paul Firmin Didot at
the Office of the Commissioners of Patents, with his Petition, on the
21st May 1855.
I, PAUL FIRMIN DIDOT, do hereby declare the nature of the said Invention
for "AN IMPROVED PROCESS OF BLEACHING PAPER PULP, TEXTILE FABRICS, AND
OTHER SUBSTANCES OR MATTERS," to be as follows:-
I effect the bleaching of paper pulp and other substances by means of
chloride of lime, or other similar bleaching chloride, acted upon by carbonic
acid gas, obtained either naturally or artificially, or even from the atmosphere
itself. The carbonic acid gas may be obtained from the combustion of char-
coal or other carbonaceous matter. I connect a pipe from a chimney or passago
containing or conveying the products of combustion to a vessel containing
water through which the gas passes, and is thus cooled and washed, and it is
further cooled, if necessary, by passing it through a worm or refrigerator.
The gas is then conducted through one or more purifiers containing shelves
covered with cloth or moss or other porous matters, moistened with water
or with purifying liquids, so as to obtain the gas free from dust and impurities.

page_text: The gas then passes to a pump with or without a regulator, which draws it
through the aforesaid apparatus, and forces it through pipes which convey it to
the vessels containing the bleaching materials. These vessels may be simple
vats or cisterns, with a perforated pipe at the bottom for the entrance of the
gas; or a vessel revolving on its axis may be employed, and the gas may
be introduced through the hollow axis and through a perforated diaphragm in
the vessel; or the gas may be introduced into the cover of the cylinder of
the beating machine employed for paper pulp or otherwise, according to the
purpose for which it is required. The conducting pipe is provided with a
hydraulic or other safety valve, to allow of the escape of the gas in the event
of the outlets being closed or obstructed. Atmospheric air may be applied
in lieu of the products of combustion, but as it contains a much smaller
proportion of carbonic acid gas, its action is much slower.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Paul Firmin Didot in the Great Seal Patent Office on
the 3rd November 1855.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, PAUL
FIRMIN DIDOT, Chemist, of Paris, in the French Empire, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-first day of May, in the year of our
Lord One thousand eight hundred and fifty-five, in the eighteenth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Paul Firmin Didot, Her special licence that I, the said
Paul Firmin Didot, my executors, administrators, and assigns, or such
others as I, the said Paul Firmin Didot, 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
"AN IMPROVED PROCESS OF BLEACHING PAPER PULP, TEXTILE FABRICS, AND OTHER
SUBSTANCES OR MATTERS," upon the condition (amongst others) that I, the
said Paul Firmin Didot, 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 of the said Invention, and in what manner
the same was to be performed, and cause the same to be filed in the Great

page_text: Seal Patent Office within six calendar months next and immediately after
the date of the said Letters Patent.
NOW KNOW YE, that I, the said Paul Firmin Didot, do hereby declare
the nature of the said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the fol-
lowing statement thereof, reference being had to the accompanying Drawing,
and to the figures and letters marked thereon, that is to say:-
I effect the bleaching of paper pulp and other substances by means of
chloride of lime, or other similar bleaching chloride, acted upon by carbonic
acid gas. By employing carbonic acid gas to decompose the chloride, the
bleaching effect is produced with rapidity without the danger of injuring the
paper pulp or other substance which arises when sulphuric acid or other strong
acids are employed.
The accompanying Drawing represents an apparatus adapted for carrying
out my Invention. Figure 1 is a vertical section of the apparatus; Figure 2
is a plan of the same. The same letters refer to similar parts in all the
Figures. A is a chimney or passage which brings a supply of carbonic acid
gas to the apparatus. This carbonic acid gas may be derived from the com-
bustion of coke or other carbonaceous matter, or from a lime kiln, or from the
decomposition of carbonates by acids, or from any other source.
a is a pipe
which conducts the gas to the lower part of a vessel b, which is partly filled
with water, and serves to wash the gas and to saturate it with water. A
vertical glass tube & communicates at both ends with the vessel b, and serves
to indicate the level of the water in the vessel. " is a cock for drawing off
the water when it becomes too much charged with foreign matters. The gas
passes through a tube c from the top of the washing vessel into a worm or
refrigerator d, and into a close chest e, furnished with a cock f for drawing off
any condensed water. The worm d is inclosed in a worm tub or vessel g, at
the bottom of which enters a current of cold water supplied by the pipe h.
The hot water runs off by the overflow pipe or spout i. When the gas arrives
at the apparatus in a cold state this refrigerator and the chest e arc not
required. From the top of the chest e proceeds a pipe j, which branches or
divides into two pipes at k, so as to communicate at pleasure with either of the
two purifiers 1, , by opening the cock m, which communicates with 7, or the
cock m', which communicates with . The purifiers 1, l', are truncated conical
vessels of wood or metal, furnished in the interior with a series of shelves of
wicker or trellis work n, n', n", n, n, about eight inches apart. These
shelves are covered with moss or wool or other porous material, moistened
if required; or the shelves may be replaced by a series of frames covered

page_text: with wet or dry cloth or felt, or other material sufficiently porous to allow
of the passage of the gas while retaining any dust or mechanical impurities.
The two purifiers communicate with each other by the pipes o, o', which pass
from the top of each vessel to the bottom of the other, as shewn in the transverse
section, Figure 3. Two pipes 9, 9', with cocks 1, 1, pass from the tops of the
purifiers to a double-acting air pump s, s', shewn on a larger scale in Figure 4.
Thus, by opening the cocks m, p, and r', and closing the cocks m', p', r, the
gas will enter the purifier 1, and after ascending through the shelves will pass
down the pipe o to the bottom of the purifier l', and, ascending through its
shelves, will pass off through the pipe q'. On the other hand, by closing the
cocks m, p, r, and opening m', p, r, the gas will pass first through the
purifier, and then through 7, and by the pipe q to the pump. By closing
the cocks p, p', the communication between the two purifiers is cut off. Tho
gas may then be directed through either by opening the cocks m, r, and closing
m', r', or vice versa. The purifier, which is thus thrown out of use, may be
opened and charged afresh, or the impurities removed from it, and it is then
again connected by opening and closing the cocks, so that the gas may enter it
after passing through the other purifier.
The pipes t, t', convey the gas from the pump s, s', to a horizontal pipe or
main u, from which proceed the branch pipes v, v, vl, vl, each of which is
provided with a cock at its upper part, and communicates with a horizontal
pipe or spiral perforated with holes, and placed at the bottom of the vats or
vessels a, a, a, a, or other vessels containing the paper pulp or other
materials which are to be bleached, and which are mixed with water and
chloride of lime or other bleaching chloride. If the apparatus employed for
the bleaching be a horizontal cylinder turning upon its spindle, which is hollow
and perforated with holes, the gas may bo introduced by one extremity of the
spindle, and its passage arrested by a diaphragm near the opposite extremity.
The holes beyond the diaphragm then serve for the escape of the gases which
accompany the carbonic acid gas, while the carbonic acid gas itself acts upon
the materials in the vessel. The carbonic acid gas may also be introduced
into the hood or cover of the cylinder of the washing or cutting engine of the
paper mill employed for reducing the rags to pulp. By this arrangement of
apparatus the carbonic acid is conducted with facility to the places in which its
action is required.
From the extremity of the horizontal pipe or main u a safety tube y is con-
ducted to the bottom of a vessel of water of sufficient depth to produce a
pressure about double that produced by the bleaching vessels. This safety tube
allows of the escape of the gas, and prevents accidents in the event of the pump

page_text: being put in motion when all the cocks of the branch pipes are closed, or in
the event of the perforations becoming obstructed. To render the current of
gas more constant, a regulator may be placed between the pump and the
main. In this apparatus the principal use of the washing vessel is to saturate
the hot gas from the chimney with water, so as to prevent it from drying the
moistened materials in the purifiers, which if dry might not completely arrest
the dust and smoke or soot which may accompany the carbonic acid gas.
The carbonic acid gas may be obtained by decomposing chalk or other
carbonate of lime by muriatic or sulphuric acid, and the gas may thus be
generated in a close vessel, and forced by its own pressure through the materials
to be bleached. It may be purified by passing it through a washing vessel
containing water. The carbonic acid gas may be obtained by any other of the
known processes for that purpose. Textile fabrics and similar articles are
immersed in a mixture of water and chloride of lime or other bleaching
chloride, and the carbonic acid gas is passed through them, as herein-before
described.
Having now described the nature of the Invention, and in what manner the
same is to be performed, I wish it to be understood that what I claim is,
the bleaching of paper pulp, textile fabrics, and other substances or matters,
by mixing them with chloride of lime, or other bleaching chloride, or immersing
them in a solution of the same, and passing or diffusing carbonic acid gas
through the mixture, as herein-before described.
In witness whereof, I, the said Paul Firmin Didot, have hereunto set
my hand and seal, this Twentieth day of October, in the year One
thousand eight hundred and fifty-five.
Witness,
CHARLES ARMENGAUD, Ing" Civil,
PAUL FIRMIN DIDOT. (L.B.)
6, Rue Filles du Calvaire, à Paris.