Nitroso Dyes

a group of dyes; aromatic compounds containing a nitroso group, NO, in the ortho- position to an OH group. The most important nitroso dyes in industry are derivatives of 1-nitroso-2-naphthol.

Nitroso dyes are produced by the action of sodium nitrite on aromatic hydroxy compounds in acid medium. Type BS green mordant dye is the product of the addition of sodium bisulfite, NaHSO₃, to 1-nitroso-2-naphthol. The complex of this dye with divalent iron is a green pigment; it is resistant to the action of light and heat and is commonly used for dyeing rubbers, in the production of wallpaper and pencils, and in the paint and varnish industry. The green pigment obtained directly on cotton fiber from BS green mordant dye gives insufficiently stable colors.

Type 4Zh acid green dye, which is a complex of iron and 1-nitroso-2-naphthol-6-sulfonic acid, is used in dyeing wool, silk, and wallpaper and for coloring soap.