More important are Kekule's observations that nitrous acid oxidizes pyrocatechol or [I.2]-dioxybenzene, and protocatechuic acid or [3.4]- dioxybenzoic acid to dioxytartaric acid, (C(OH) 2 COOH) 2 (Ann., 1883, 221, p. 230); and 0.
Meyer, which are formed when nitrous acid acts on primary aliphatic nitro compounds.
In acid solution, potassium permanganate oxidizes it to nitric acid, but in alkaline solution only to nitrous acid.
It may be prepared by the fusion of para-toluene sulphonic acid with potash; by the action of nitrous acid on para-toluidine; or by heating para-oxyphenyl acetic acid with lime.
Both classes readily exchange the imide hydrogen for acid radicals, and give nitrosamines with nitrous acid.
