Lignin was isolated from Cajanus cajan (Pigeon pea; Bengali : arhar).
Lignosulphonic acid resin was prepared from this lignin and characterised by
pH titration. This lignosulphonic acid showed titration characteristics
resembling those of soluble strong acids. Addition of electrolytes to water
increased the ion-exchange capacity. Sorption of moisture by lignosulphonic
acid showed a gradual moisture gain upto about 80% relative humiduty which
was followed by a sharp increase of moisturegam upto 100% relative
humidity.