Determination of the molar volumes and the estimation of electrostriction of electrolytes from an investigation of the density dependence of very dilute solution of electrolytes on their concentrations

A magnetically controlled total immersion hydrometer is described. Changes in upthrust due to changes in density of the solution are balanced by adjusting the current in a suitably placed coil. A simple relationship between the coil current and the density increment permits the density of the solution as a function of concentration of solute to be investigated to a high degree of accuracy. The electrolytes of 1:1, 2:1, 1:2 valence types and four tetra-alkyl ammonium salts are investigated. In all these cases the density shows a linear function of concentration over the concentration range of 5.53 x 10N to 3.32 x 10NThe molar volumes at infinite dilution calculated from our experimental results show slightly higher values in most of the electrolytes investigated. However, in cases of KF, Na2CO3, Mgcl2, Sncl2 and KOH the values of the molar volumes deviate considerably from the presently available values.The electrostriction estimated on the basis of the densities of the molten state of the electrolytes is comparable to that estimated by Mukherjee. In cases of 1:1 electrolytes the electrostriction varies from 3 ml/moleto 11 ml/mole and in cases of 1:2 electrolytes from 44 ml/moleto 53 ml/mole with an exception of Na2CO3. The electrolytesof 2:1 valence type show electrostriction around 30 ml/mole with a number of exceptions. In cases of all the four tetra-alkyl ammonium salts the electrostriction is found negative around - 20 ml/mole.