Low Shear Capillary Viscometer with Continuously Varying Pressure Head

A capillary viscometer is described for the study of the flow behavior of non-Newtonian fluids at shear stresses of 0.06–20 dynes/cm2. The all-glass instrument consists of two units connected by a ball joint, one unit of which contains the capillary while the second is essentially a manometer. As the test fluid moves through the capillary, the rate of rise of the fluid in the manometer is observed. This measurement of the column height as a function of time allows calculation of both pressure drop and rate of flow. Different combinations of capillary and manometer units can be employed interchangeably to study liquids of widely varying viscosities. Data and methods are presented which show that the instrument can be used to determine the absolute viscosities of Newtonian liquids and the flow curves of non-Newtonian fluids over the indicated shear stress region.