Measurements of the Self-diffusion of Water in Pure Water, H2O-D2O Mixtures and Solutions of Electrolytes.

The self-diffusion of water was measured at 25.0 deg in pure water, H/ sub 2/O-D/sub 2/O mixtures, and solutions of NaCl, LiBr, and MgSO/sub 4/. The diffusion cells used were of the shearing boundary type and are described. Deuterium and performed by means of a mass spectrometer. Tritium was detected by means of liquid scintillation technique, or by an improved version of the bremsstrahlung method. Comparative measurements in pure water at 25.0 deg C with deuterium and tritium is tracers gave identical results (2.25 plus or minus 0.02) X 10/sup -5/ cm/sup 2//sec) with those obtained from measurements on H/sub 2/O-D/sub 2/O mixtures using a precision optical method. The result thus indicates that the isotope effect is within experimental error. The self- diffusion of water in H/sub 2/O-D/sub 2/O mixtures, having tritium as tracer. seems to decrease linearly with the increase in deuterium content. The self- diffusion coefficient in dilute salt solutions was very moderately affected. In concentrated solutions decreasing effects were most pronounced in solutions of MgSO/sub 4/. A comparison of the inverse viscosity versus solute concentration with the self-diffusion shows a similar course for the two functions. The results in the case of salt solutions are discussed brieflymore » in terms of the theory of Wang. Data of others are included for comparison. (auth)« less