Improvements in Mordanting.
Year: 1898

page_text: Date of Application, 25th Apr., 1898-Accepted, 20th Aug., 1898
COMPLETE SPECIFICATION.
Improvements in Mordanting.
I, FRITZ HABER, of Karlsruhe, in the Grand Duchy of Baden, Germany, Doctor
of Philosophy, and Private Lecturer on Technical Chemistry in the Karlsruhe
Technical College, do hereby declare the nature of this invention, and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:―
In dyeing cotton one of the mordants used is chromium in the form of chromic
salts or combinations of chromic oxide.
Of the latter, both chromic salts, in which hydrated chromic oxide is the base,
and sodium chromite, in which hydrated chromic oxide is the acid, are used,
The processes in which salts of chromium oxides are employed are based on two
principles either the goods are first soaked in a rich solution of a chromic salt
and the absorbed salt decomposed in a bath of soda, sodium phosphate, lime, or
other similar substances, whereby the hydrated chromic oxide is separated and
deposited upon the fibre; or the cotton is treated first of all with an acid mordant
(tanning principles, or Turkey-red oil) and mordanted with a solution of chromic
salt. In the latter case the fibre, charged with acid mordant, abstracts from the
chromic salt solution a part of the metallic hydrate that it contains, which latter
becomes fixed on the fibre. A further treatment in lime, soda, or similar precipi-
tant completes the fixing of chromium on the fibre.
Now I have found that chromium is more readily taken up by cotton if the
latter first of all charged with the hydrate, carbonate, or tannate of an alkaline
earth such as lime water, calcium carbonate, or calcium tannate, and afterwards
boiled in a solution of a chromium salt such as chromic sulphate, chromic-nitrate,
or fluoride of chromium.

page_text: The best dyeing is obtained when the mordanting is effected in the manner set
forth in Example III, as chromium is then taken up so easily and to such an
extent that two skeins weighing each 20 grammes absorb the whole of the chromium
contained in a solution of 2.5 grammes of fluoride of chromium in 0.75 litre of
water, the said chromium becoming fixed on the fibre. The whole of the chromium
used can therefore be utilized successfully as a mordant, so that the fibres can be
charged with chromium by using the least possible amount of chromic salt that
theory would indicate.
In consequence of the extraordinary ease and richness with which the mordant-
ing action takes place, colours of especial fulness and fineness are obtained when
dyeing cotton so mordanted by means of mordanting dyes. The colours so ob-
tained are, moreover, unaffected by soap.
Having now particularly described and ascertained the nature of the said in-
vention and in what manner the same is to be performed, I declare that what I
claim is:-
1. A process of mordanting cotton by means of chromium which consists in
charging the cotton first with the hydrate, carbonate, or tannate of an alkaline
earth and then heating it in a solution of a chromium salt.
2. Mordanting cotton in the improved ways herein described.
F. WISE HOWORTH,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.