SUMMARYFor the interpretation of kinetic measurements involving m-chloroaniline hydrochloride, the dissociation constant of the latter was determined at 5, 15, 25 and 35OC, in sodium chloride solutions of 0 to 3 mole/], using a modified distribution method (l). The distribution of m-chloroaniline between petroleum ether and aqueous sodium chloride solutions, was studied under the same conditions. The activity coefficients of the amine in aqueous solution, were determined at these conditions. The thermodynamic dissociation constant of the amine hydrochloride,at zero molality, was estimated at the different temperatures. AH, AF and AS were calculated.