Equilibrium Adsorption Values of Leuco Vat Dyes on Cotton

The equilibrium adsorption of a series of leuco vat dyes on cotton has been measured in various concentrations of sodium chloride and sodium hydroxide. From the results the thermodynamic affinities have been calculated. Deviations from theory are observed in so far as the affinities are not constant, but show a regular drift as the concentration of electrolyte is changed. This drift is more apparent when the added electrolyte is sodium chloride than when it is sodium hydroxide. Two explanations for these deviations from theory are proposed and discussed— either the theory is inadequate to account for the facts, or the leuco solutions of the dyes are not true solutions but are in fact aggregated.