IMPROVEMENTS IN THE TREATMENT OF OAK AND OTHER WILD SILKS FOR BLEACHING AND DYEING
Year: 1875

page_text: PROVISIONAL SPECIFICATION left by Charles Denton Abel at the
Office of the Commissioners of Patents, with his Petition, on the
10th April 1875.—A communication from abroad by Cyprien Marie
Tessié du Motay, of Paris, France, Chemist.
I, CHARLES DENTON ABEL, of No. 20, Southampton Buildings,
Chancery Lane, in the County of Middlesex, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN THE TREATMENT OF OAK
AND OTHER WILD SILKS FOR BLEACHING AND DYEING," to be as follows:-
Grey silks such as are produced from oak and other vegetable matters
commonly known as wild silks, cannot be bleached by alkalies, nor by
soaps, nor by these combined with sulphurous or other acids. When
they are subjected to the action of nascent oxygen alone, or with
sulphurous or arsenious acid, they become partially bleached, under-
going a kind of slow combustion, which destroys the fibre before com-
pletely removing the colour, and thus permanganates and chromates
of alkalics or alkaline earths and oxygenated water supplying nascent
oxygen bleach wild silks very slowly, at the same time injuring their
fibre Again, when subjected to the alternate action of nascent oxygen
and sulphurous acid on the one hand, and of sulphuretted hydrogen and

page_text: sulphurous acid on the other, wild silks do not become completely
bleached without serious weakening of their fibre.
To overcome these difficulties the following process, which forms the
subject of the present Invention, is applied:-The wild silks aro
immersed for about a quarter of an hour in a weak bath containing
about 2 per cent. of permanganate of an alkali or alkaline earth, and
then the pellicule of sesqui-oxide of manganesc formed on their fibres is
dissolved by sulphurous or arsenious acid. This operation is repeated
several times till the colour of the fibres has become changed from the
deep yellow to a clear grey, when they are subjected to the action of
sulphuretted hydrogen, either in the gascous or liquid form, or as
alkaline hydrosulphates or sulphides. The fibres are then carefully
washed in pure water containing no metallic salts, and are subjected to
the action of sulphurous acid. After this they are treated several times
as first described with permanganates and sulphurous acid, then with
sulphuretted hydrogen or hydrosulphates and sulphurous acids until the
grey tint is quite removed.
The method above described is particularly applicable to grey silks for
preparing them for dyeing in clear tints. When such silks are to be
dyed in deep colours that can be developed without boiling with alkali
or soap, the treatment with nascent oxygen and sulphurous or arsenious
acid suffices. It must be understood however that all wild silks when
thus only partly bleached are damaged by boiling with alkalies; but if
they have been treated with the alkaline permaganates without the
sulphurous acid they are not attacked by boiling alkali or soap. For
dying them in dark colours they may be several times immersed in the
permanganate bath, and allowed to retain the pellicule of sesqui-oxide of
manganese which becomes alternately dissolved by cyanides, giving a
fine black dyc.