IMPROVEMENTS IN THE PRE- PARATION OF BLEACHING MATERIALS OR COMPOUNDS
Year: 1866

page_text: LETTERS PATENT to Thomas Gray, of Wandsworth, in the County of
Surrey, Bleacher, for the Invention of "IMPROVEMENTS IN THE PRE-
PARATION OF BLEACHING MATERIALS OR COMPOUNDS."
Sealed the 24th April 1867, and dated the 7th December 1866.
PROVISIONAL SPECIFICATION left by the said Thomas Gray at the
Office of the Commissioners of Patents, with his Petition, on the 7th
December 1866.
I, THOMAS GRAY, of Wandsworth, in the County of Surrey, Bleacher, do
hereby declare the nature of the said Invention for "IMPROVEMENTS IN THE
PREPARATION OF BLEACHING MATERIALS OR COMPOUNDS," to be as follows:-
It is well known that chloride of lime is the substance or compound usually
employed for bleaching fabrics and fibres, and that unless the process be
carefully conducted there is risk of injuring or weakening the fabric or fibres
under operation. It is believed that this arises from the presence of free acid
in the bleaching compound, and that this acid not only injures or weakens the
fibres but also retards the bleaching operation.
The object of the present Invention is to eliminate this acid from the
bleaching compound, or at any rate to neutralize it, so that even if the acid
be present it will be inert.

page_text: I have discovered various ways of effecting this object, but the particular
process to be employed must depend upon the circumstances of the case to
be treated.
The ordinary method of manufacturing bleaching powder consists in
impregnating ground lime with chlorine gas, but as this nearly always contains
free acid one of my processes consists in passing the chlorine gas through a
solution of caustic soda or other alkali in water before allowing it to enter the
chamber or vessel in which it is brought in contact with the lime.
Sometimes it will be found more convenient to mix soda ash, caustic
soda, or other alkali with the ground lime, so that when the chlorine gas is
brought to the lime the free acid may combine with the soda ash or caustic
soda or other alkali, and thus remain inert in the compound.
As a modification of this latter process the soda ash or other caustic alkali
may be intimately mixed in a pulverized state with bleaching powder or
chloride of lime made in the ordinary manner.
I have described above three modes of bringing the alkali into the presence
of free acid for the purpose of neutralizing the same, but I do not intend to
confine myself thereto, although I believe the modes described will in practice
be found the most convenient.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Thomas Gray in the Great Seal Patent Office on the 6th
June 1867.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
GRAY, of Wandsworth, in the County of Surrey, Bleacher, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Seventh day of December, in the year of our Lord
One thousand eight hundred and sixty-six, in the thirtieth year of Her reign,
did, for Herself, Iler heirs and successors, give and grant unto me, the said
Thomas Gray, Her special licence that I, the said Thomas Gray, my executors,
administrators, and assigns, or such others as I, the said Thomas Gray, 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 THE PRE-
PARATION OF BLEACHING MATERIALS OR COMPOUNDS," upon the condition (amongst

page_text: others) that I, the said Thomas Gray, 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 Seal Patent Office within six calendar months next and
immediately after the date of the said Letters Patent.
1
NOW KNOW YE, that I, the said Thomas Gray, do hereby declaro
the nature of my said Invention, and in what manner the same is to bo
performed, to be particularly described and ascertained in and by the following
statement (that is to say):-
'
It is well known that chloride of lime is the substance or compound usually
employed for bleaching fabrics and fibres, and that unless the process bo
carefully conducted there is risk of injuring or weakening the fabric or fibres
submitted to the action of the chlorine. It is believed that this arises from.
the presence of free acid in the bleaching compound, and that this acid not
only injures or weakens the fibres, but also retards the bleaching operation.
י
The object of the present Invention is to eliminate this acid from the-
bleaching compound, or at any rate to neutralize it, so that even, if. the acid
be present it will be inert.
I have discovered various ways of effecting this object, but the particular
process to be employed must depend upon the circumstances of the case to
be treated.
The ordinary method of manufacturing bleaching powder consists in
impregnating ground lime with chlorine gas, but as this gas nearly always
contains free acid, one of my processes consists in conducting, the chlorine gas
direct from the retort to a vessel containing a solution of caustic soda or other
alkali dissolved in water in the proportion of from one to two ounces to the
gallon of water, and causing the chlorine gas to pass through such alkaline
solution, so as to neutralise the free hydrochloric acid mixed therewith before
allowing it to enter the chamber or vessel in which it is brought in contact
with the lime. Instead of neutralising the free acid by passing the gas through
an alkaline solution before bringing it into contact with the lime, it will some-
times be found more convenient to mix the soda ash, caustic soda, or other alkali
in a solid but pulverized state with the ground lime, so that when the chlorine
gas is brought into contact with the lime the free acid may be caused to combine
with the soda ash or caustic alkali, and thus remain inert in the compound.
When this process is adopted I mix the soda ash with the line in the pro-
portion of two ounces of soda ash to one pound of lime, but I do not confine
myself to these exact proportions.

page_text: As a modification of this latter process the soda ash or other caustic alkali
may be intimately mixed in a pulverized state, in the proportions already
stated, with bleaching powder or chloride of lime made in the ordinary
manner..
I have described above three modes of bringing the alkali into the presence
of the free acid for the purpose of neutralizing the same, but I do not intend to
confine myself 'thereto, although I believe the modes described will in practice
be found the most convenient.
Having now described my Invention of "Improvements in the Preparation
of Bleaching Materials or Compounds," and having explained the manner of
earrying the same into effect, I claim as the Invention secured to me by
Letters Patent as aforesaid, neutralizing the free acid contained in bleaching
compounds or chlorine gas by passing the gas through an alkaline solution
previous to bringing it into contact with the lime with which it is to be com-
bined, or mixing some suitable alkali with the ground lime or with the
bleaching powder previous to using the same for bleaching purposes, as herein
set forth.
;
In witness whereof, I, the said Thomas, Gray, have hereunto set my
hand and seal, the Thirty-first day of May, in the year of our Lord
One thousand eight hundred and sixty-seven.
THOMAS GRAY.
L.S.)