IMPROVE- MENTS I BLEACHING HEMP, FLAX, AND OTHER FIBROUS SUBSTANCES
Year: 1854

page_text: LETTERS PATENT to Charles Watt, of 17, Gloucester Gardens, Gloucester
Place, Kentish Town, Practical Chemist, for the Invention of "IMPROVE-
MENTS I
BLEACHING HEMP, FLAX, AND OTHER FIBROUS SUBSTANCES.
PROVISIONAL SPECIFICATION left by the said Charles Watt at the Office
of the Commissioners of Patents, with his Petition, on the 18th April
1854.
I, CHARLES WATT, of 17, Gloucester Gardens, Gloucester Place; Kentish
Town, Practical Chemist, do hereby declare the nature of the Invention for
"IMPROVEMENTS IN BLEACHING. HEMP, FLAX, AND OTHER FIBROUS SUBSTANCES" to
be as follows:-
The fibrous substance to be, operated on is to be. first heated for three or
four hours in a weak solution of caustic alkali- (I prefer caustic soda), at the
temperature of 190° Fahrenheit. The strength of, the alkali greatly depends
on the quality and condition of the fibrous substance. The. fibrous substance
is now to be removed from the alkali and placed in a cold and weak solution
of a chlorite or hypochlorite (I prefer those of soda). The strength of this
solution must also depend on the quality of the fibrous, substance. In some
cases it is necessary to place the fibrous substance a second time in the caustic
alkali after the immersion in the solution of the chlorite or hypochlorite.
The fibrous substance is now ready for bleaching. This may be effected by
exposing it to the action of hypochlorous acid, chlorous acid, or chlorine; but I
greatly prefer the first-named acid.

page_text: The most convenient method of bleaching by hypochlorous acid is to place
the fibrous substance in a weak solution of a hypochorite (I prefer the hypo-
chlorite of soda), and to liberate the hypochlorous acid by means of hydrochloric
or any other acid. I prefer the following modus operandi:-
The fibrous substance is placed in an open crate or basket, made of any
suitable material. This crate or basket should be made of sufficient length to
hold the hanks of flax, hemp, or other fibrous substance without doubling them.
The fibrous substance should be placed about six inches in depth on the bottom
of the basket. A frame is then made to fit on stops in the crate or basket, at
about two inches from the top of the fibrous substance; and on this frame another
layer of fibrous substance of the same thickness is to be placed, and so on, until
the basket is full. The basket thus charged is then let down by means of a
small travelling crane into the alkali, and afterwards transferred to the other
solutions. This is a convenient method of immersing the fibrous substances to
be operated on in the various solutions, as it saves the necessity of removing
them in small quantities from the different vats, and preserves them from
becoming entangled.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Charles Watt in the Great Seal Patent Office on the 18th
October 1854. -
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
WATT, of 17, Gloucester Gardens, Gloucester Place, Kentish Town, Practical
Chemist, send greeting.
WHEREAS. Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Eighteenth day of April, in the year of our Lord One
thousand eight hundred and fifty-four, in the seventeenth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Charles Watt, Her special licence that I, the said Charles Watt, my executors,
administrators, and assigns, or such others as I, the said Charles Watt, 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 BLEACHING HEMP, FLAX, AND
OTHER FIBROUS SUBSTANCES," upon the condition (amongst others) that I, the
said Charles Watt, by an instrument in writing under my hand and seal,

page_text: 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.
NOW KNOW YE, that I, the said Charles Watt, 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 following statement
thereof (that is to say) :-
My Invention consists in bleaching hemp, flax, and other fibrous substances
of a similar nature, such as jute and others, by subjecting them to the action of
an alkali, and afterwards to the action of chlorite or hypochlorite of soda, or
other base; and I prefer to repeat the action of these substances two, three, or
more times alternately, until the fibre is sufficiently acted upon; and I then
complete the bleaching by the action of hypochlorous acid or other suitable
bleaching agent. And in order that my said Invention may be most fully
understood and readily carried into effect, I will proceed to describe the manner
in which I prefer to operate in practice. I take the raw fibre in the hanks in
which it is found in commerce, and I place these hanks in a wicker-work
basket of sufficient length to hold the hanks without doubling them, until a
layer of about six inches in depth has been formed on the bottom of the basket.
I then place in the basket a frame of wicker-work, which rests on stops in the
basket at about two inches from the top of the layer of fibre; on this frame I
place another layer of fibre, and then another frame, and so on, until the
basket is filled. I then, by means of a crane, lift the basket and deposit it with
its contents in a copper of suitable size and form, which copper contains a
solution of caustic soda at a temperature of about 190° and of a density of 7°
Beamé, or thereabout. In this solution I keep the fibre for about four hours,
and maintain the temperature all the time at the degree above named, except
when I am treating the coarser kinds of fibres, and then I have found it to be
advantageous to allow the temperature to rise to the boiling point. When the
fibre has remained for a sufficient time in this solution I lift the basket out of
the copper by means of the crane. When the fibre has drained, the basket is
lowered into a vessel containing water (by preference warm), and I change the
water in this vessel until the alkali is well washed out of the fibre. When this
is accomplished, the basket with its contents is removed into a wooden vessel
containing a solution of chlorite or hypochlorite of soda; but I employ the
hypochlorite by preference. The specific gravity of this solution should
generally be about 1.100; but this I fix by experiment for each different
quality of fibre, that is to say: I subject several small samples of the fibre in

page_text: question to the action of different proportions of hypochlorite, and thus I find
the proportion which is most suitable; but I would remark, that this solution
should not be employed of a greater strength than is necessary, otherwise the
fibre is liable to be injured by it.
After the fibre has remained for about three quarters of an hour in this
solution, I remove it therefrom and again wash it with water,
These processes, viz, immersion in alkali, washing and immersion in hypo-
chlorite of soda, and washing, I repeat until the alkali ceases to remove any-
thing from the fibre. When this point is arrived at, the fibre is again washed,
and in place of being immersed in the solution of hypochlorite, which has been
employed up to this point, it is immersed in a much weaker, solution of the
same salt, (say, of 1-033 specific gravity, to which is then added hydrochloric
acid to liberate the hypochlorous acid, by which the bleaching is completed.
When this action has been carried sufficiently far, the fibre is again washed,
and the process is complete.
Having this described the nature of my Invention, and the manner of per-
forming the same, I would have it understood that I do not confine myself to
the exact details described; but what I claim is, the subjecting fibrous materials
to the combined action of an alkali, and of the chlorite or hypochlorite of soda
or other base, as before described.
In witness whereof, I, the said Charles Watt, have hereunto set my hand
and seal, this Eighteenth day of October, in the year of our Lord One
thousand eight hundred and fifty-four.
CHARLES WATT. (L.S.)
Witness