Viscosity Determination by the Oscillating Vessel Method I: Theoretical Considerations

When a liquid is placed in a vessel held by a torsional suspension and the whole is set in rotation about a vertical axis, the viscosity of the liquid may be deduced from observations of the time period and decrement of the oscillations. This method of measuring viscosity has many practical advantages, but there are mathematical difficulties in making the calculations. The cases of spherical and cylindrical vessels are considered in detail and formulae are obtained for the calculation of the viscosity which are very accurate and easier to use than those previously proposed. The case of an axially symmetrical vessel which departs slightly from the spherical form is also considered, and formulae (valid only when the frequency of oscillation is high) are obtained for an axially symmetrical vessel of any shape. Corrections for the effect of external air resistance are also discussed.