Year: 1888

page_text: I, EMILE MARIE HIPPOLYTE ANDREOLI, Journalist of 62 Loughborough Park
Brixton S.W. Surrey 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 :-
In the Specification No. 8161 filed on the 4th of June last by me I described the
advantages of bleaching paper pulp and other fibrous substances by Electricity with
charcoal electrodes, either in the shape of slabs, broken pieces or of sticks retained &
fixed between a network of lead wire etc.
I have since ascertained that the denser the wood the better the conductivity of the
charcoal & that only such charcoal is serviceable for Electricity which has been twice
submitted to a slow carbonization in closed vessels and afterwards brought gradually
to a high temperature.
Priestley was the first to observe this fact that a bad conductor of electricity such
as baked wood could become a very good conductor of the electric current under the
influence of heat and after him (leevreusse 60 years ago proved by his experiments,
now forgotten and generally ignored that charcoal may or may not conduct electricity
and heat and that when it conducts one it conducts the other, and besides that, if it
does not conduct heat it does not conduct electricity.
Such properties are very little known and many people think that charcoal does
not conduct electricity or heat. If, however, two pieces of the same branch of a tree
are submitted to distillation in a retort until no fumes are evolved, the two pieces of
charcoal, being of the same nature and having been carbonized in the same manner
during the same time, will have the same properties. and neither will be good
conductors. But if one of these pieces of charcoal is put again into the retort and
heated until it is red the two pieces of charcoal will no longer resemble one another
and the one which has been carbonized only once will not conduct electricity, while
the other will conduct it very well.
It is extraordinary that charcoal well baked and afterwards well purified has not
yet been utilized for Electro-chemical purposes because there is no other body which
resists better the corroding action of Oxygen or Clilorine.

page_text: One of the drawbacks of charcoal used for Electrodes is its lightness but it may
be obviated by means of a frame of denser material which prevents the charcoal from
swimming swinging and causing short circuits.
I have found that it is far better to make plates rods, blocks, cylinders, shects etc.
of pulverized wood charcoal or any vegetable charcoal powder mixed with a suitable
agglutinating substance, such as sugar or its equivalents readily transformable into
pure carbon and then moulded compressed & baked until a carbon is produced which
is highly conductive, homogenous, has the same strength throughout, a uniform density
and resists the corrosive and destructive action of Chlorine, Oxygen, Ozone etc., better
than the usual Carbon Electrodes which are attacked, disintegrated & deteriorated as
the positive poles in an electrolytic tank containing a Chloride of Sodium solution which
turns black with the formation of a black deposit of mellogen or mellic acid or
graphitic acid according to the nature of the carbon.
I can make charcoal electrodes by means of boxwood dust or any other hard wood
dust which I mix with the adhesive syrupy substance and which I compress into slabs
or run into sticks, rods etc. and carbonize, but I generally use charcoal crushed to a
sufficiently fine powder and which I treat first in a strong alkaline solution & when
well washed and steamed is subjected to the action of fluoric or Hydro-chloric Acid
which destroys all the extraneous matters and leaves only charcoal in a state of pure
carbon which I mix with a solution of sugar & malaxate until it forms a paste which
I submit to hydraulic or steam pressure and which is afterwards baked in a closed
oven in the usual manner.
When cooled this cake is thrown into a pulverizing machine and its powder is
once more mixed & malaxated with syrup until it forms again a thick paste to which
I give the required shape of slabs, sticks, rods etc.
The mouldings and bakings of such charcoal electrodes are effected by one of
the well known processes in the art of manufacture of gas retort or other carbons
for electrical purposes. But I make a point of having the charcoal electrodes
submitted at least twice to the heat of the oven or retort and before each baking,
immersed and boiled in a bath of sugar syrup or Glucose because the syrup penetrates
into the pores and when the plate or rod is heated to red heat in a closed vessel or
retort there is in all its small cells, cavities, interstices or pores, a deposit of hard
sugar carbon which is chemically pure and embodied with the charcoal and makes
dense electrodes having all the required properties for the electrolytic operation,
hardness, non-resistance density, homogeneity and which besides are almost
indestructible or at least will neither he corroded nor attacked or destroyed in
such a great degree as retort carbon, graphite, or other forms of carbon when used
in an alkaline or other electrolytical bath. I must say that I also use electric carbons
of superior quality, and more especially Carbons for Electric Arc lamps, as anodes
in presence of a Carbon Cathode or any other convenient cathode, in a solution of
Chloride of Sodium which I decompose by the electric current in order to bleach
paper pulp or other vegetable substance, and that by adopting certain devices and
precautions, such electrodes will be of good service and resist for a certain length of
time the action of Oxygen and chlorine provided the solution of Chloride of Sodium
is strong and also provided I use alternating currents so that if the plates are attacked
even slightly they each wear out equally because both the positive and the negative
electrodes are alternately used during the same time as an anode and that the destructive
action at the positive pole has hardly time to attack the carbon on which Oxygen is
immediately replaced by Hydrogen and so on.
In the, bleaching process of vegetable substances we also found that to make sure
of the almost indestructibility of my wood charcoal or vegetable charcoal electrodes
I use concentrated solutions of chloride of Sodium and also alternating currents and
in this way I avoid the formation of a black deposit of mellogen or mellic acid &c.
and the electrolyte is never black but is perfectly limpid, of a transparent greenish
colour when the liquid is acid and whitish when alkaline.
In order to have a more powerful action on the electrolyte I preferably use electrodes.
composed of prismatic or cylindrical sticks or rods such as those which are employed

page_text: in electric arc lamps made of charcoal or otherwise as hereinbefore described of which
I make a sort of grid or grate in the following manner.
1st. I dip the upper ends of the carbons in sulphate of copper or other copper
solution and send an electric current through the solution using the carbons as Cathodes
so that they will be coated with copper.
2nd. After they have been coppered I tin this film of copper with common solder
and place the required number of rods all the tinned ends together in a grooved
receptacle which holds them firmly side by side equally distant one from another so
that I have only (30) to dip the emerging tinned ends in a bath of molten lead to have
an electrode which will act more powerfully than a plate or a block of carbon or of
compressed charcoal powder.
4° On the top of the lead coating all along I solder & firmly attach a strong copper
or brass rod and I dip (5°) the whole into a bath of insulating material to protect the
metal against the action of the electrolytic bath and in order to give more solidity to
such grids or grates of carbon rods which might easily break (6°) The lower ends
of the rods pass through the holes of a piece of wood which on both sides is attached
to two other pieces of wood which are fastened to the copper rod & therefore form a
strong frame.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
.
The bleaching of vegetable substances by means of Anodes and Cathodes of wood
charcoal or vegetable or animal charcoal of any required form obtained as herein before
described and also by means of Electric Arc carbons employed as anodes and cathodes
in an electrolytic tank in conjunction with a chloride solution in the manner herein-
before substantially described.