IMPROVE- MENTS IN DYEING BLACK AND GREY AND IN PREPARING MATERIALS THEREFOR
Year: 1867

page_text: PROVISIONAL SPECIFICATION left by Edouard George Peter Thomas at
the Office of the Commissioners of Patents, with his Petition, on the
9th October 1867.-A communication from abroad by Jules Persoz,
residing at Rue Madame, Paris, Chemist.
I, EDOUARD GEORGE PETER THOMAS, of the Butts, Brentford, in the County
of Middlesex, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN DYEING BLACK AND GREY AND IN PREPARING MATERIALS THEREFOR,"
to be as follows:-
At the present time there are well known processes by which an aniline
black color may be printed upon cotton, but there is no known process by which
either wool or cotton can be successfully dyed with aniline black. These
results may however be attained by the following processes :-
To Dye Wool. The wool is first mordanted by maintaining it for about an
hour in a boiling bath composed in the following manner :—
Water
Bichromate of potash
Sulphate of copper
Sulphuric acid
- 1 litre
10 grammes
-
6
1
"
The wool is then washed and introduced into a bath of oxalate of aniline
containing a slight excess of oxalic acid. This bath, which should contain
about 40 grammes of oxalate per litre of water will enable the dyer to obtain
in a few moments a most intense black. The wool should not be dipped
into the bath until the latter has acquired a temperature of about 40°
centigrade; the heat must then be continued, but it should not be raised to
the boiling point.

page_text: The process just described may be modified both as to mordanting and
dyeing. Thus it is not necessary to adhere strictly to the relative proportions of
the substances employed in mordanting, some of them may even be replaced
by analogous reagents; as, for example, instead of the sulphate of copper the
perchlorides of copper and iron, the sulphates of alumina and zinc, and the per-
sulphate of iron may be used. In dyeing the mordanted wool a somewhat
smaller or somewhat larger quantity of oxalate of aniline may be employed and
a black dye nevertheless obtained; it is even possible to substitute for oxalate
of aniline some other salt of aniline such as the hydrochlorate, the nitrate, the
sulphate, the arseniate, but in that case a quantity of oxalic acid must be
added to the bath equal or nearly equal to the quantity which it would have con-
tained bad the oxalate of aniline itself been used. The order of the operations
may also be reversed by first charging the wool with a salt of aniline and then
passing it through a hot bath of bichromate of potash; lastly, the wool may be
plunged into a cold bath containing both bichromate of potash and oxalate of
aniline, but these different modifications possess no advantages over the process
first described.
To Dye Cotton. The cotton is mordanted in a bath well known to calico
printers containing a mixture of oxide of lead, or of a salt of lead and of milk
of lime, and then passed into a hot bath of bichromate of potash so as to form
chromate of lead upon the fibre. The dyeing is then performed in the same
manner and under the same conditions as already described for wool. The
black product which fixes itseif upon textile fibres when the process is con-
ducted in the, manner above described may be obtained in an isolated form by
mixing the solutions of bichromate of potash and of oxalate of aniline or of
any aniline salt to which oxalic acid has been added. In a short time, if in
the cold, and immediately if under the influence of heat, a black precipitate is
formed which should be collected and washed. This substance is soluble in
alcohol and methylated spirit to which a littlo sulphuric acid has been added.
This solution when poured into a large quantity of water forms a bath which
communicates to silk and wool a more or less dark shade of grey.
I mean by aniline the commercial product sold under that name which often
contains besides aniline the homologues of aniline, toluidine, cumidine, and
others in variable proportions.