Abstract
A falling co-axial cylinder viscometer has been developed for the rapid measurement of absolute viscosities over the range 5 × 104 to 1010 poises under known constant shearing stresses. The apparatus consists essentially of an inner hollow brass composite cylinder encircled by a brass cylindrical ring with a space between to contain the test material. Details in design that facilitate measurement and manipulation include devices for centering the inner cylinder during filling and during test; direct application of load to a lower extension from the inner cylinder, which provides stability to the falling system by ensuring that it remains vertical; and ability of the inner cylinder to travel an equal distance on either side of the mean position. The main advantages of this instrument are: (1) It can be filled easily and brought to test temperature in about half an hour. (2) Manipulation is simple. (3) Only about 12 c.c. of material are required for test. (4) A reasonably wide range of viscosities can be measured by the same apparatus. Although the instrument is satisfactory for purely viscous materials it is not suitable for measuring the viscosities of materials having pronounced plastic (non-Newtonian) or elastic properties.