IMPROVEMENTS IN DYEING WOOL AND SILK FABRICS OR MATERIALS
Year: 1874

page_text: PROVISIONAL SPECIFICATION left by John Garrett Tongue at the
Office of the Commissioners of Patents, with his Petition, on the
25th April 1874.-A communication from abroad by Ivar Bang,
Chemist, of Paris, France.
:
I, JOHN GARRETT TONGUE, of the Firm of Tongue & Birkbeck,
Patent Agents and Engineers, of 34, Southampton Buildings, Chancery
Lane, in the County of Middlesex, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN DYEING WOOL AND SILK FABRICS OR
MATERIALS," (communicated to me from abroad by Ivar Bang, Chemist,
of Paris, France,) to be as follows:-
This Invention relates to a new method of obtaining a dye upon
stuffs or yarns of woollen material and silk the color being known as
French blue and cyanide of blue, the object of the Invention being the
application of a mixture of red cyanide and a salt of iron at the
maximum to obtain in dyeing a much larger deposit of blue upon
the fabric, fibres, or threads of wool or silk, and to prevent the disengage-
ment of prussic acid. Hitherto in order to obtain these colors the wool
or silk is usually dyed in a bath containing ferrocyanide of potassium,

page_text: sulphuric acid, and an alum or other mordant, according to the usual
practice of different dye works, but the true coloring matter is the
ferrocyanide which under the influence of sulphuric acid is resolved into
sulphate of potash and into ferrocyanhydric acid, which latter gradually
subsides upon the woollen fabric or material being destroyed by heat,
thereby forming a blue which remains fixed upon the wool, the
cyanhydric acid being disengaged. The quantity of cyanogen thus used
for the production of the blue is not the half of that which is contained
in the ferrocyanide, the other half being lost in the form of prussic
acid which is injurious to the health of the workpeople employed.
The object of this Invention is to employ nearly if not all the
cyanogen contained in the ferrocyanide in the formation or production
of the blue and consequently preventing all dangerous emanations. For
this purpose red cyanide mixed with a salt of iron is used at a maximum
in equal parts, but sometimes the proportions are varied according to
the shade or tint required. It is thus in reality the ferrocyanide of
peroxide of iron, which is employed. This salt is perfectly soluble, it
subsides gradually on the wool or silk, and is transformed by heat into
a blue which remains permanent. There is thus obtained nearly double
the gain in color as compared with pure cyanide.
In order to obtain a shade or tint upon wool or silk half less of the
red cyanide is taken than in the ordinary mode of working. The same
mordants are used and acids, according to the custom of particular
works, and a quantity of the salt of iron is added to the maximum
judged necessary, according to the calculation of the equivalents or from
the shade it is desired to obtain.
The operation of dyeing is conducted absolutely as if with the cyanide
alone. The wool can also be previously mordanted with peroxide of
iron and then dyed in a bath of acidified ferrocyanide, but this process
is more complicated.