99—THE ADSORPTION OF NON-IONIC DYES BY WOOL

Abstract

Linear isotherms have been obtained on wool, at 40°, 60° and 80°C, with derivatives of azobenzene. In most cases with truly non-ionic dyes, the plot of –δμ°/RT against 1/T also appears to be linear, indicating a constant heat of dyeing. With the weakly acidic 4-carboxy- and 4-sulphonamido-azobenzene, and the weakly basic 2,4-diaminoazobenzene, the heat of dyeing is not constant, probably owing to variation in the extent of ionization at different temperatures. The most soluble of the truly non-ionic dyes examined also showed a variable heat of dyeing. Non-ionic dyes have low affinity for wool and, consequently, low fibre saturation values.