The Chemistry of Dyestuff. Dyestuffs. XV. Nitroso and Nitro Dyestuffs.

A Manual for Students of Chemistry and Dyeing
By
M. Fort, M.Sc. (Leeds) Late Lecturer in Dyeing in the Bradford Technical College and L. L. Lloyd, Ph.D. (Bern) Lecturer in Organic and Technical Chemistry in the Bradford Technical College
Cambridge: at the University Press 1919
(First edition 1917, reprinted 1919)Nitroso Dyestuffs. - A small group obtained by the action of nitrous acid (NaNO 2 + HCl) on phenols. The introduction of the chroinophore group NO gives colour, and when orthoto the hydroxy group also gives mordant dyeing properties. These dyes are usually applied in conjunction with iron, giving dull green shades of good fastness to light and washing, being much used in printing of fabrics.

Fast Green O (paste) (M.),
Dark Green (paste) (0.), Resorcine Green, etc.
[-]
Gambine R (R.H.), l-oxy-2-nitrosonaphthalene.
Gambine Y (R.H.), 2-oxy-l-nitrosonaphthalene.
Gambine B (R.H.), l-nitroso-2.7-dioxynaphthalene.
Naphthol Green B (C.) is obtained by use of a phenol sulphonic acid from which [-] is obtained by the usual method. It is marketed as an iron salt, having one atom of iron (Fe") united with two of the above molecules and is used mainly for wool.

Nitro Dyestuffs. - A few acid products coloured yellow in virtue of possessing the chromophore groupNO₂ are used as dyes.

Picric Acid or symmetrical trinitro -phenol, described previously among the intermediate products, finds a limited use as an acid dye.

Martins Yellow, Naphthalene Yellow, etc., is prepared similarly to picric acid, i.e., from the 2.4-disulphonic acid of α-naphthol.

[-]

It appears on the market as ammonium, sodium or calcium salt.

Naphthol Yellow S. - Obtained by nitration of l-naphthol-2.4.7-trisulphonic acid or of the 1.2.7or 1.4. 7-disulphonic acids. It is obtained as potassium or sodium salt.

[-]

It is very extensively used as an acid dye, and has almost entirely replaced Martius Yellow.

The standard of fastness in the nitro dyes is only fair.

The nitro dyestuffs, like the nitroso dyestuffs, are destroyed on reduction, forming colourless amido compounds.