Production of Blue Dyestuffs.
Year: 1891

page_text: Date of Application, 15th May, 1891
Complete Specification Left, 12th Feb., 1892-Accepted, 26th Mar., 1892
PROVISIONAL SPECIFICATION.
Production of Blue Dyestuffs.
I, SYDNEY PITT, of Sutton, in the County of Surrey, Gentleman, (a communi-
cation to me from abroad by Leopold Cassella & Co., of Frankfort-on-Main, in
the Empire of Germany, Manufacturing Chemists,) do hereby declare the nature
of this invention to be as follows:--
This invention has for its object the production of blue dyestuffs.
The known methods of producing thionine dyestuffs from dimethylaniline cannot
be used for the production of analogous derivatives of dimethyl o. toluidine, because
the latter cannot he transformed into a nitroso compound. The present Specifi-
cation relates to a process for obtaining the toluthionines of which the following
is an example. The new dyestuffs are distinguished by their great intensity.
Example: 165 kilos. of the nitrosamine of monomethyl (or ethyl) o. toluidine
are dissolved at about 5° C. in 150 kilos. of strong muriatic acid. After standing
some hours the clear solution which then contains the hydrochlorate of paranitroso-
monomethyltoluidine (NOC,H,NHC,H,) is diluted with water and cooled with
ice. It is reduced by means of 13 kilos. of zinc dust. As soon as the liquid has
become colorless, the free mineral acid is neutralised and 24.8 kilos. of thiosulphate
of soda and shortly afterwards 10 kilos. of bichromate of potash are added. Then
the solution of 17-2 kilos. of hydrochlorate of monomethylorthotoluidine is intro-
duced. The oxidation is performed by adding first 120 kilos. of chloride of zinc
and then 30 kilos. of bichromate of potash. The liquid is heated to the boil.
The coloring matter is separated from the residue which contains the chrome.
It forms small green crystals. It dyes on cotton mordanted with tannic acid a
pure blue.
In this example instead of monomethyl o. toluidine being used as the second
component other amines may be employed such as o. toluidine, dimethylaniline,
diethylaniline.
Dated thi
1
CARPMAEL & Co.,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Production of Blue Dyestuffs.
I, SYDNEY PITT, of Sutton, in the County of Surrey, "Gentleman, (a communi-
cation to me from abroad by Leopold Cassella & Co., of Frankfort-on-Main, in
the Empire of Germany, Manufacturing Chemists,) 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 :----
This invention has for its object the production of blue dye-stuffs.
The known methods of producing thionine dyestuffs from dimethylaniline cannot
be used for the production of analogous derivatives of dimethyl o. toluidine, because
the latter cannot be transformed into a nitroso compound. The present Specifi-
cation relates to a process for obtaining substituted toluthionines which are
distinguished by great intensity & pure shades. The general process is the
following. P. amido-monoalkyl o. toluidine (which can easily be prepared from
monoalkyl o. toluidine) is oxydized in presence of thiosulphuric acid & the
p. amido-monoalkyl o. toluidinethiosulphonic acid thus obtained is condensed with
[Price 8d.]

page_text: monoalkyl o. toluidine (or o. toluidine, dimethylaniline, diethylaniline) by simul-
taneous oxydation. The product of condensation is transformed into the dyestuff
by heating it to about 100 deg. C. with water which contains condensing salts
(chloride of zinc) & a sufficient quantity of an oxydizing agent (bichromate).
Example: 165 kilos. of the nitrosamine of monoethyl (or methyl) o. toluidine
are dissolved at about 5 deg. C. in 150 kilos. strong muriatic acid. After standing
for some hours, the clear solution, which then contains the hydrochlorate of para
nitroso monocthyltoluidine (NOC,H,NHC₂H) is diluted with water & cooled with
ice. It is reduced by means of 15 kilos. of zinc dust. As soon as the liquid has
become colorless, the free mineral acid is neutralised & 24-8 kilos. of thiosulphate
of soda & shortly afterwards 10 kilos. of bichromate of potash are added. Then
the solution of 17-2 kilos. of hydrochlorate of monoethyl o. toluidine is introduced.
After addition of a concentrated solution of 120 kilos. of chloride of zinc the
oxydation is performed by means of 30 kilos. of bichromate of potash. The liquid
is heated to the boil & is kept boiling for about one hour. The dyestuff separates
from the liquid, mixed with oxide of chrome. The precipitate is filtered off &
the coloring matter is isolated by extracting the residue with hot water. It is
obtained from the solution by addition of common salt, in the shape of small green
crystals. It dyes cotton, mordanted with tannic acid, a pure blue.
Having now particularly described & ascertained the nature of my said inven-
tion & in what manner the same is to be performed, I declare that what I
claim is:
1.) The process of preparing thionine dyestuffs from p. amidomonoalkyl o. tolui-
dine substantially as described.
2.) The new coloring matters hereinbefore described.
Dated this 30th dore of Lana 1809
CARPMAEL & Co.,
Agents for the Applicant.