Streaming Birefringence and Optical Relaxation Time of Vanadium Pentoxide Sols

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Abstract
Maxwell constant and optical relaxation time is studied for V2O5 sols having concentrations which range from 0.01 to 0.1 volume percent using mercury green, 5461 A, and mercury red light, 6000 to 6800 A. These quantities were measured in a device which sheared the sols between two coaxial discs, that is, in a direction which corresponds to the radial one in a Couette device. The Maxwell constant ranged from about 1.5×10−2 to about 4.5×10−6 cm2/dyne for freshly made sols and from about 8.0×10−2 to 2.9×10−5 cm2/dyne for the same sols when they were 29 days old. It is shown that the Maxwell constant for these sols was an exponential function of concentration and that the optical relaxation time and Maxwell constant could be related for them. Because the Maxwell constant is an exponential function of sol concentration, it is suggested that the expression for the rotary diffusion constant of an infinitely dilute sol of rod‐shaped particles can be made applicable to more concentrated sols by multiplying it by the term (esC−1)/sC, where C is concentration and s is the slope of the curve relating sol concentration to Maxwell constant, to account for the change in particle interaction with change in sol concentration. The viscosity and spectral transmission of these sols were also checked. It was found that the viscosity ranged from 1.0 cp for the most dilute sol to about 1.25 cp for the sol of concentration 0.1 volume percent. These sols were found to have a transmission which peaked at about 6800 A and dropped rapidly on either side of this value.