Reaction of Sulphur Dioxide with Image Transfer Azo-Naphthol Dyes

Abstract

Mordanted azo-naphthol cyan dyes have been shown to be susceptible to attack by atmospheric sulphur dioxide to yield a magenta product. The reaction is catalysed by the presence of water. It is also reversible. The rates of the forward and back reactions are strongly influenced by the structure of the dyes. The reaction involves the addition of HS0₃- to the naphthalene ring, yielding a 3-sulphonated tetrahydroxynaphtllalene.