Etude des propriétés diélectriques de solutions aqueuses diluées d'électrolytes forts I. La constante diélectrique

A new bridge method has been used for measuring dielectric constants of dilute aqueous electrolytic solutions. Sodium, potassium and barium chloride, and potassium iodide have been used at molalities ranging from 10−4 to 5.10−3 mole per 1000 gr water. Measurements have been carried out at frequencies varying between 10 and 400 kilocycles per second. Electrode effects were observed in all cases, and corrections according to Oncley's formula were applied. Final results are claimed to be accurate to 0,5%. Dielectric constants for extremely dilute solutions were very close to that of pure water. For molalities lower than one millimole per 1000 grs water, dielectric increments were compatible with the theory of Debye and Falkenhagen. At higher concentrations dielectric constants showed a sharp decrease. This may be due to a saturation effect, but this hypothesis should be confirmed by measurements at still higher concentrations.