The density fluctuations contributing to light scattering in a glass are governed by the fictive temperature of the glass and the equilibrium compressibility of the melt. Using ultrasonic velocity data for KzO-Si02 melts, these compressibilities were evaluated, and the magnitude of the density fluctuations were calculated. In this system, the mean-square amplitude of the fluctuations ,reaches a minimum value (about half that of pure SiO,) for a composition of ~2 0 mol% KzO. By extrapolating the equilibrium compressibilities to zero K20 content, the density fluctuations can be calculated for pure SiOz glass; this calculation agrees well with the result obtained from lightscattering measurements.

The viscosity of a 0.60KNQ ,-0.40Ca(NQ melt was measured from 10 " to 10" P by a beam-bending method. In this range, the viscosity exhibited Arrhenius behavior, with an activation enthalpy of 138 kcal/mol. These data joined smoothly with capillary and rotational viscometer data from to 10" P previously reported for this system. The temperature dependence of shear sound wave velocities at 75.2 MHz was measured, and the temperature dependence of the shear modulus from 60" to 120°C was calculated for this melt. The Fulcher equation, In g = A + B / ( T -T O ) , described the temperature dependence of the viscosity of this melt poorly, indicating severe deficiencies in the viscosity theories which predict an equation of this form.

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