Improvements in the Treatment of Bleaching Powder to Preserve it from Loss of Active Chlorine.
Year: 1896

page_text: Date of Application, 31st Aug., 1896.
Complete Specification Left, 31st May, 1897-Accepted, 17th July, 1897.
PROVISIONAL SPECIFICATION.
Improvements in the Treatment of Bleaching Powder to Preserve it
from Loss of Active Chlorine.
I, JAMES YATE JOHNSON of 47 Lincoln's Inn Fields in the County of London
Gentleman do hereby declare the nature of this Invention (which has been
communicated to me from abroad by Chemische Fabrik Electron "Actien Gesellschaft"
of Frankfort-on-Main in the Empire of Germany) to be as follows:-
Bleaching powder in time gradually loses its active chlorine more particularly in
transport and at raised temperatures, all precautions in packing, and in choice of
packing material having hitherto failed to prevent decomposition. In consequence
it is almost impossible to import into hot climates or remote districts bleaching powder
of high chlorine value.
In addition to the influence of light, it is well known that the decomposition of
bleaching powder is attributable to the action of carbonic acid and moisture in
atmospheric air, inasmuch as the carbonic acid completely drives out the chlorine,
whilst the presence of moisture enables the metallic salts to behave as oxygen carriers.
On exposure to air, therefore, bleaching powder rapidly loses the whole of its active
chlorine.
In view of this fact it is desirable to pack bleaching powder in closed vessels, perfectly
air-tight and light-tight, as for instance, sealed cases of metal. But in order to ensure
protection, it would be necessary to employ thick cases, which would not only be
expensive themselves, but would also increase the cost of transport. With a loose material
of the consistence of bleaching powder, thin cases cannot be employed, since external
pressure or blows would dent the sides so much as to render it impossible to preserve
the case intact. The occurrence of even a single perforation, moreover, is sufficient
to cause decomposition of the material, consequent on the admission of air, when all
the iron cases of a whole shipment rapidly become eaten through (vide Lunge, Soda
Industry III, p. 418; 1890).
Since the injurious influence of the atmosphere cannot be counteracted in the
manner indicated, there remains only the alternative of converting the bleaching
powder into a solid, cohesive, inass by pressure, the moisture set free from the slaked
lime on conversion into hypochlorite acting as the binding agent. It is an important
and noteworthy fact that under the influence of pressure the density inay be raised
froin 0.7 or 0.75 to 1.6, without any rise of temperature, or exhibition of elastic action.
Compressed bleaching powder of this density is quite odourless and as hard as
limestone, resisting successfully the decomposing influence of air, even when freely
exposed to it. Whilst air is free to circulate through ordinary bleaching-powder,
penetrating the loose mass, and giving up to it carbonic acid and moisture, compressed
bleaching powder offers for attack only the infinitely smaller surface which the
outside of the block or cake presents. This becomes covered with a thin, damp film
of calcium carbonate, which effectually prevents an entrance of external air.
Such powerful compression, however, is not exerted without some difficulty, and as,
moreover, bleaching powder in this hardened form dissolves rather slowly, experiments

page_text: were made with the substance less highly condensed, when it was found possible to
produce bleaching power of specific gravity 1.0 or 1.1, exhibiting the useful properties
already mentioned, at the same time possessing the advantage of being readily
convertible, even after storage or transport, into a sandy powder almost free-from
lumps.
Investigation of the keeping qualities of this bleaching powder in warm chambers,
has justified the opinion that the compressed substance, even of high chlorine
value, is quite fit for export to warm climates. Bleaching powder compressed direct
in iron drums 05-07 millimetres in thickness, was found to have lost none of its
active chlorine after exposure to a temperature of 35° Centigrade during a period of
five weeks, and in the same condition it withstood a trial journey from Germany to
the United States. The technical outcome of the compression of bleaching powder is
one which has been sought for since the production of bleaching powder becaine an
industry, and is in consequence of great importance; the essential points in the
process may be summed up as follows.
The iron cases required for the perfect preservation of ordinary bleaching powder are
much too costly to fiud general application in the industry, but for compressed
bleaching powder they are highly suitable, becoming even cheaper and considerably
lighter than wood, as in contrast to the uncompressed substance, it may be packed in
drums made of very thin sheeting, the compressed material imparting strength and
rigidity to the drums, so that change of shape or perforation of the walls becomes
almost impossible. If, however, the drums suffer damage through careless handling
in transport, experience has shown that decomposition does not spread to the interior
of the mass.
Apart from other advantages, the increased specific gravity, by reducing the bulk
of the material, plays an important part in minimising the cost of transport by
lowering the freight charges.
The lumps occurring in ordinary blenching powder are disintegrated, after pressure,
into a sandy powder, in this way facilitating the process of solution.
The sandy powder obtained on breaking up the compressed substance does not give
rise to the dust and offensive odour of the ordinary material, thus obviating any
injurious results from its manipulation.
Dated this 31st day of August 1896.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.
Improvements in the Treatment of Bleaching Powder to Preserve it
from Loss of Active Ohlorine.
I, JAMES YATE JOHNSON, of 47 Lincoln's Inn Fields, in the County of London,
Gentleman, do hereby declare the nature of this invention (which has been com-
municated to me from abroad by Chemishe Fabrik Electron Actien-Gesellschaft,
of Frankfort-on-Main, in the Empire of Germany) and in what manner the same is
to be performed to be particularly described and ascertained in and by the following
statement:-
Bleaching powder in time gradually loses its active chlorine, more particularly in
transport and at raised temperatures, all precautions in packing, and in choice of
packing material, having hitherto failed to prevent decomposition. In consequence,
it is almost impossible to import into hot climates, or remote districts, bleaching
powder of high chlorine value."

page_text: In addition to the influence of light, it is well known that the decomposition of
bleaching powder is attributable to the action of carbonic acid and moisture in
atmospheric air, inasmuch as the carbonic acid completely drives out the chlorine as
sach whilst the presence of moisture enables the metallic salts present in the bleaching
powder to behave as oxygen carriers. On exposure to air, therefore, bleaching
powder rapidly loses the whole of its active chlorine.
In view of this fact it is desirable to pack bleaching powder in closed vessels,
perfectly air-tight, and light-tight, as for instance, sealed metal cases or boxes. To render
these cases or boxes absolutely secure it is necessary to make them thick which not only
makes them expensive in themselves, but also increases the cost of transport. With
a loose material of the consistence of bleaching powder, thin cases or boxes could not
hitherto be employed, since external pressure, or blows, would dent the sides so much
as to render it impossible to preserve the case or box intact. The occurrence of even a
single perforation would be sufficient to cause rapid decomposition of the material
consequent on the admission of air, when the iron cases or boxes of a whole shipment
rapidly become eaten through (vide Lunge, Soda Industry III, p. 418; 1896).
Since the injurious influence of the atmosphere cannot be counteracted in the
manner indicated, there remains only the alternative of converting the bleaching
powder into a solid, cohesive mass by pressure, the moisture set free from the slaked
lime on conversion into hydrochlorite acting as the binding agent. It is an important
and noteworthy fact that under the influence of pressure the density may be raised
from 07 or 0.75 to 1-6, without any rise of temperature, or exhibition of elastic action.
In the Specification of Letters Patent No. 5673 of 1886 mention is made of pressure
being applied to bleaching powder in casks and of compressing it into cakes or bricks
but this has not found application in practice, possibly owing to the fact that it has
not been hitherto recognised how important is the part played by the degree of
compressibility of the bleaching powder.
If for instance the bleaching powder be insufficiently compressed, the desired result
is not achieved or but incompletely achieved, whilst if the compression be too great,
there is the drawback of the substance being brought to such a condition that it.
breaks up into hard lumps requiring to be ground before it will properly dissolve, an
operation which is both tedious and injurious to health, and cannot be carried on
without loss of active chlorine, whereby the object of the process is frustrated.
This invention depends on the important discovery that at a proper degree of com-
pression as hereinafter explained bleaching powder has the property of crumbling
completely into a fine sandy powder after having been preserved for some period or
when submitted to transport with comparatively slight agitation. Bleaching powder
which previously consisted of dusty powder and lumps acquires the homogeneous
condition described.
Bleaching powder thus compressed is quite odourless and so hard as to resist
successfully the decomposing influence, of air, even when freely exposed to it. Whilst
air is free to circulate through ordinary bleaching powder, penetrating the loose
mass, and giving up to it carbonic acid and moisture, it offers for attack only the
infinitely smaller surface which the outside of the block or cake presents. This
becomes covered with a thin, damp film of calcium carbonate, which effectually
prevents an entrance of external air.
Powerful compression is not exerted without some difficulty, and as, moreover,
bleaching-powder in this hardened form dissolves rather slowly, experiments have
been made by my foreign correspondents who have found it possible to produce
bleaching-powder of specific gravity of from 10 to 09 but not over 1.0 which powder
so treated has the useful properties already mentioned, at the same time possessing
the advantage of being readily convertible, even after storage or transport, into a
sandy powder almost free from lumps.
Investigation of the keeping qualities of this bleaching powder in warm chambers,
has justified the opinion that the compressed substance, even of high chlorine value
is quite fit for export to warm climates. Bleaching powder compressed as aforesaid
in drums of iron of 0.5 to 0.7 millimètres in thickness, was found to have lost none

page_text: of its active chlorine after exposure to a temperature of 35° Centigrade during a period
of five weeks, and in the same condition it withstood a trial journey from Germany to
the United States. The technical outcome of the aforesaid compression of bleaching
powder is one which has been sought for since the production of bleaching powder
became an industry, and is in consequence of great importance; the essential points
in the process may be summed up as follows:-
The iron cases required for the perfect preservation of ordinary bleaching powder
are much too costly to find general application in the industry, but for compressed
bleaching powder they are highly suitable, becoming even cheaper and considerably
lighter than wood, as in contrast to the uncompressed substance, it may be packed in
drums made of very thin sheet metal, the compressed contents imparting strength
and rigidity to the drums, so that change of shape or perforation of the walls becomes
almost impossible. If, however, the druns should suffer damage, experience has
shwen that decomposition does not spread to the interior of the mass.
Apart from other advantages, the increased specific gravity, by reducing the bulk
of the material, plays an important part in minimising the cost of transport by
lowering the freight charges.
The lumps occurring in ordinary bleaching powder are disintegrated, after pressure,
into a sandy powder, in this way facilitating the process of solution.
The sandy powder obtained on breaking up the compressed substance does not give
rise to the dust and offensive odour of the ordinary material, thus obviating any
injurious results from its manipulation.
Having now particularly described and ascertained the nature of this
invention, and in what manner the same is to be performed, I declare that what
I claim is
The treatment of bleaching powder to preserve it from loss of active chlorine during
transit or storage and at the same time to render it capable of being readily brought
to condition for use the said treatment consisting in compressing it as hereinbefore
explained.