THE MEASUREMENT OF ABSOLUTE VISCOSITY BY THE USE OF CONCENTRIC CYLINDERS ¹

Abstract

ABSTRACT A method is described for the measurement of absolute viscosities of liquids, employing the torque exerted upon a stationary inner cylinder or spindle, suspended by means of a torsion member into the center of a fluid, when the cylindrical container is given a uniform angular motion. The “true” viscosity of the castor oil, used as a test fluid, is found by extrapolating values of apparent viscosity, given by spindles of various lengths but equal radii, to that value corresponding to infinite length. For the oil being used, the viscosity at 20°C is given by this method as 9.67 poises. Using this as the true value, the effective length and thereby the end effect in terms of additional length may be found for any spindle in a liquid of given finite boundaries. The end correction to length, so determined for a spindle of 0.5 cm. radius by 10 cm. length in the center of a liquid of boundaries 3.2 cm. radius by 13 cm. height, a system similar to that used in measuring glass viscosities, was found to be 0.44 cm.