Physicochemical investigation of a cation exchange resin (amberlite IR100) II. Resin conductance

Abstract

1. 1. The electric conductivity of swollen resin plugs packed between perforated platinum electrodes, and containing various bound cations, is investigated in a special streaming cell, which allows of replacement of one ionic species by another in the same plug. This method proves to be a useful tool in the investigation of the strength of binding of cations in the resin. 2. 2. The hydrogen resin is a fairly good conductor; the conductance of alkali metal resins is about 6–12 times smaller, while resins in which hydrogen is replaced by ions of higher valency, or silver, are poor conductors. For hydrogen and alkali metal resins, the resin conductance is roughly proportional to the mobility of the respective cations in water, but no such proportionality exists for resins containing silver or ions of higher valency. It is concluded that the latter are much more tightly bound than the former, the order being Th 4+>La 3+>>Ba ++>Ag +>Ca ++>>Mg ++>>alkali metal ions > H + 3. 3. The variation of the resistance of plugs of alkali metal resins with the pH of the salt solution used in the exchange reaction is studied. The resistance has a maximum at pH ⋍ 3.5 but falls when the pH of the salt solution is higher. It is suggested that up to pH ⋍ 3.5 the -SO 3H groups are involved, but that groups of a more weakly acid nature come into action at higher pH. There is evidence of hydrolysis of alkali metal salts of the latter groups on streaming water through the resin plug.