Falling Sphere Viscometers

A ball-and-bucket type of viscometer in which the ball is fixed and the bucket falls was used by Beal and Docksey.i A falling sphere viscometer for opaque liquids was described by McDowell and Walker, Michell s viscometer ... 

The falling sphere viscometer is employed to estimate the viscosity of a liquid by measuring the stationary falling velocity of a sphere in the liquid. The falling velocity is determined by measuring the time required for the sphere to pass between the upper and lower lines in the container shown in Figure 12-6. 

Figure 12-6. Falling sphere viscometer. The cylinder is immersed in a thermostat to control the temperature of the liquid.

Thereafter, using Eqs. (6.4) and (6.5) and knowing the densitjr of the ball and of the hquid allows the determination of the viscosity of the viscous liquid. Falling sphere viscometer can be used for high-pressure measurement, as those carried out in a superpress. Pressure indeed appears to change viscosity. Free volume theory refinements (see Section 6.1.3.4) incorporate pressure dependence. Viscosities of sihcates and aluminosilicates are reported to decrease with increasing pressure. 

Appendix D Falling Sphere Viscometer and Fining of Glass... 

When a falling sphere viscometer is used, one supposes that the asymptotic regime is reached or the transient regime (from velocity v = 0 to Vi) is achieved. This regime is obtained solving... 

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