IMPROVEMENTS IN THE APPLICATION OF CHLORIDE OF LIME FOR BLEACHING AND OTHER PURPOSES
Year: 1884

page_text: PROVISIONAL SPECIFICATION.
By GEORGE LUNGE, of Zurich in the Republic of Switzerland, professor of
chemistry do hereby declare the nature of said invention for IMPROVEMENTS IN THE
APPLICATION OF CHLORIDE OF LIME FOR BLEACHING AND OTHER PURPOSES, to be
as follows:-
Many proposals have been made for increasing the action of solutions of chloride
of lime, commonly called bleaching powder, by the addition of agents which
liberate from it chlorine of hypochlorous acid. Hydrochloric, sulphuric or oxalic
acid, when employed for this purpose, cause the evolution of free chlorine which
acts too strongly upon the fibres and is injurious both to the health of the workmen
and the machinery. Carbonic acid does not liberate chlorine, but hypochlorous
acid; but its gaseous. state is inconvenient for its practical application, and it
causes the precipitation of calcium carbonate within the fibres, which is also the
case with the action of bleaching powder in the ordinary way, and which compels
finishing the operation by, "souring," that is, steeping, in weak hydrochloric
or sulphuric acid.
I have discovered that an agent, hitherto not employed for this purposo, combines
all the advantages of the materials formerly employed without any of their draw-
backs. This is acetic acid, or any other weak organic acid of analogous nature.
Its price is no impediment, for a minimal quantity is sufficient, the same being
regenerated over and over again. At first acetic acid and chloride of lime
decompose into calcium acetate and free hypochlorous acid. In the bleaching
process the latter yields its oxygen, hydrochloric acid being formed. The latter
instantly acts upon the calcium acetate; calcium chloride is formed and acetic is
regenerated, which decomposes a fresh quantity of chloride of lime, and so forth.
Consequently the smallest quantity of acetic acid suffices for splitting up any
amount of chlorido of lime into calcium chloride and active oxygen. These
reactions are shown by the following equations:

page_text: The hydrochloric acid formed according to equation
No 2.) is never present in the free stato, as it instantly acts upon calcium acetato,
according to equation.
No 3.) This is very important, since hydrochlorid acid weakens the fibre by
prolonged contact, whilst acetic acid is quite harmless. Since there are no insoluble
calcium salts present, the operation of "souring" after the bleaching is quite
unnecessary; this not merely saves the expense of the acid and of the subsequent
washing of the fabrics, but it also avoids the danger, especially present in the case
of stout fabrics, of leaving some of the acid in the stuff, which concentrates on
drying and weakens the fibre; it may also prove injurious for subsequent dyeing
processes, but in the new process no free acid is present except acetic acid which
has no action upon the fibre even in the concentrated state and at a high
temperature.
The acetic acid may be employed in various ways of which the following are
only specimens. A small quantity of it may be added from the first to a solution
of bleaching powder; or the fabric, after being, treated in the ordinary way with a
solution of bleaching powder, may be steeped, without previous washing, in water
containing a little acetic acid; or the fabric may be steeped in water containing a
little acetic acid and a solution of bleaching powder subsequently run in slowly
_and_gradually, with continuous agitation; or any other suitable means of using it
may be employed, according to the various-nature-of-the-materials to be treated.
In the case of hard water or of impure solutions of bleaching powder a good deal
of acetic acid would be consumed for neutralizing the lime; in this case some
hydrochloric or sulphuric acid may be added-in order to effect this neutralization;
but the quantity of mineral acids should never exceed that required for this object,
so that never any acid except -hypochlorous or acetic acid oxists in the free-state
If the proper precautions-are-taken, there is a considerable saving of bleaching
powder in comparison with the ordinary process, and the water courses-are-less-
fouled.
My process is applicable to the bleaching of vegetable fibres in the unspun-state,
or spun, or woven, for locally discharging many colours, such as alizarine red; for
bleaching puper pulp made of rags, wood, esparto and the like; for manufacturing
wood pulp direct from woody fibre and for many other purposes.
Whenever in this description the words "acetic acid" are used there should be
understood: "or any other weak organic acid of analogous nature, such as formic
acid and several others."
What I claim as my invention is: employing acetic acid, or other weak organic
acids of analogous naturo, in order to increase and hasten the action of chloride of
lime, and to save the usual operation of "souring" after the bleaching, without
injuring the fibre in any way.
Dated this Thirteenth day of Angust 1884.

page_text: COMPLETE SPECIFICATION.
I, GEORGE LUNGE, Doctor of Philosophy, Professor of chemistry, of Zurich in
the Republic of Switzerland, do heroby doclare the nature of said invention for
IMPROVEMENTS IN THE APPLICATION OF CHLORIDE OF LIME FOR BLEACHING AND
OTHER PURPOSES and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
Many proposals have been made for increasing the action of solutions of cbloride
of lime, commonly called bleaching powder, by the addition of agents which
liberate from it chlorine or hypochlorous acid. Hydrochloric, sulphuric or oxalic
acid, when employed for this purpose, cause the evolution of free chlorine, which
acts too strongly upon the fibres and is injurious both to the health of the workmen
and the machinery. Carbonic acid does not liberate chlorine, but hypochlorous
acid; but its gaseous state is inconvenient for its practical application, and it
causes the precipitation of calcium carbonate within the fibres, which is also tho
case with the action of bleaching powder in the ordinary way, and which compels
finishing the operation by "souring," that is, steeping in weak bydrochloric or
sulphuric acid.
I have discovered that an agent, hitherto not employed for this purpose, combines
all the advantages of the materials formerly employed, without any of their draw-
backs. This is acetic acid, or any other weak organic acid of analogous nature.
Its price is no impediment, for a minimal quantity is sufficient, the same being
regenerated over and over again. At first acetic acid and chloride of lime
decompose into calcium acetate and free hypochlorous acid. In the bleaching
process the latter yields its oxygen, hydrochloric acid being formed. The latter
instantly acts upon the calcium acetate; calcium chloride is formed and acetic acid
is regenerated, which decomposes a fresh quantity of chloride of lime and so forth.
Consequently the smallest quantity of acetic acid suffices for splitting up any
amount of chloride of lime into calcium chloride and active oxygen. These
reactions are shown by the following equations:
2.) 2 HO CI = 2 H Cl + 0.
3.) Ca (C₂ H, O₂)2 + 2 H Cl = Ca Cl₂ + 2 C, H, O..
The hydrochloric acid formed according to equation (2) is never present in the
free state, as it instantly acts upon calcium acetate, according to equation (3).
This is very important, since hydrochloric acid weakens the fibre by prolonged
contact, whilst acetic acid is quite harmless. Since there are no insoluble calcium
salts present, the operation of "souring" after the bleaching is quite unnecessary;
this not merely saves the expense of the acid and of the subsequent washing of the
fabrics, but it also avoids the danger, especially present in the case of stout fabrics,
of leaving some of the acid in the stuff, which concentrates on drying and weakens
the fibre; it may also prove injurious for subsequent dyeing processes. But in the
new process no free acid is present except acetic acid, which has no action upon the
fibre, even in the concentrated state and at a high temperature.

page_text: The acetic acid. may be employed in various ways of which the following are
only specimens. A small quantity of it may be added from the first to a solution
of bleaching powder; or the fabric, after being treated in the ordinary way with a
solution of bleaching powder, may be steeped, without previous washing, in water
containing a little acetic acid; or the fabric may be steeped in water containing a
little acetic acid, and a solution of bleaching powder subsequently run in slowly
and gradually, with continuous agitation; or any other suitable means of using it
may be employed, according to the various nature of the materials to be treated.
In the case of hard water or of impure solutions of bleaching powder a good deal
of acetic acid would be consumed for neutralizing the lime; in this case some.
hydrochloric or sulphuric acid may be added in order to effect this neutralization;
but the quantity of mineral acids should never exceed that required for this object,
so that never any acid except hypochlorous or acetic acid exists in the free state.
If the proper precautions are taken, there is a considerable saving of bleaching
powder in comparison with the ordinary process, and the water courses are less
fouled.
My process is applicable to the bleaching of vegetable fibres in the unspun state,
or spun, or woven; for locally discharging many colours, such as alizarinė red; for
bleaching paper pulp made of rags, wood, straw, esparto and the like, and for other
Whenever in this description-the-words "acetic acid are used, there should_be_
understood: "or any other weak organic acid of analogous nature, for-instance-
formic acid."
Having now particularly described and ascertained the nature of my said
Invention, and in-what-manner-the-same is to be performed, I declare that what
I.clnim is
Employing acetic acid, or other weak organic acids-of-analogous nature, in order
to increase-and-hasten the action of chloride of lime, and to save the usual operation
of "souring" after the bleaching, without injuring the fibre-in-any-way..