The viscometer of the lifting liquid type here reported is composed of two steel balls of different diameters, which are hung on the two arms of a balance. Both the hanging fibers are of equal diameter. The balls are immersed in the liquid to be examined, and the vessel of the liquid is drawn up with a desired constant velocity.
In contrast with the viscometer of the lifting liquid type with a single ball previously reported, it is unnecessary to take into account the change of the length of fiber immersed in the liquid and the surface tension.
With a constant drawing-up velocity the difference of the viscous drags acting on the two balls (ƒ
1-ƒ
2) is determined by maintaining the equilibrium of the balance. The coefficient of viscosity η can then be obtained by ƒ
1-ƒ
2=6πη (
rl-
r2)
v, asauming Stokes' law of viscosity.
The results show that the coefficients of viscosity thus calculated depend on the lifting velocity, and the limiting values corresponding to the zero lifting velocity coincide with the true values.
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