| Popis: |
The Stokes formula for calculation of viscosity of a fluid fails badly when applied over the range 10 to 10,000 poises under ordinary conditions. Many viscosity data based on this relation which is valid only for a medium infinite in extent appear seriously in error. Several published corrections also fail but the Faxen relation, based on strict hydrodynamic theory, gives results in good agreement with values obtained by the improved capillary tube technique. Viscosity measurements on glycerol and “Viscous Oil” by the falling sphere method agree with values reported by Armour & Co., and by the Bureau of Standards over the range 7 to 3660 poises with maximum differences of less than 1%. Considerable practical as well as scientific interest attaches to the findings above since the requirements of apparatus and technique for measurement of absolute viscosities over a wide range with high accuracy are simple, inexpensive and generally available. The method is especially well suited for the range 10 poises and upwards and has been used in commercial research. |
