The conductances of solutions of picric acid in various ketones and nitriles have been measured over a concentration range from 0.04 x 10-3 to 100 x 10-3 g-equiv./l., the temperatures employed being 15", 25", and 40°C. A new conductance equation is developed on the assumption that triple ions of one type only are formed. The experimental results of the present investigation are examined on the basis of ion pair, triple ion, and modified (unilateral) triple ion formation. It is shown that the preferential formation of one type of triple ion can best explain the variation of conductance with concentration in these systems.

The conductance of picric acid in chlorbenzene, a-chlor-and a-bromnaphthalene has been investigated at 25" C over a concentration range of 14-06 to 0.04 X 10-3 g equiv./l. by a d.c. method, and the results are presented. A variation of conductance with time has been observed for solutions of picric acid in various ketones and nitriles, but is absent from solutions in halogenated hydrocarbons and in water. An explanation, supported by spectrophotometric measurements, is offered on the basis of a slow ionization process which may be associated with the proton acceptor properties of the solvent. E X P E R I M E N T A LAll solutes, and the ketones and nitriles used as solvents, were purified, and all solutions prepared as described in the earlier part of this work.9 Conductance cells and electrodes, determination of cell constants, and temperature control were also as previously described. The halogenated hydrocarbons were purified by first drying over anhydrous CaC12. The chlorbenzene was then subjected to repeated fractional distillation at atmospheric pressure, the first and last fractions being rejected each time. The two halogenated naphthalenes were repeatedly fractionally distilled at reduced pressure, and again only the middle fractions were collected The physical constants obtained for these solvents were as follows :