CannonFenskeViskometer

The Cannon-Fenske viskometer is a type of glass capillary viskometer used for measuring the kinematic viscosity of transparent Newtonian liquids. It is a suspended-level type viskometer, meaning the liquid level in the lower reservoir is not fixed. This design helps to minimize errors caused by surface tension effects. The viskometer consists of a U-shaped glass tube with two bulbs connected by a capillary. The liquid's flow time through a precisely calibrated capillary tube under gravity is measured. This flow time, when multiplied by a viskometer constant specific to the instrument, yields the kinematic viscosity.

To use a Cannon-Fenske viskometer, a sample of the liquid is placed in the larger bulb. The viskometer is then inverted and immersed in a constant temperature bath. After thermal equilibrium is reached, air is blown into the lower tube to draw the liquid up into the upper bulb until it is above the upper timing mark. The air pressure is then released, and the time it takes for the liquid meniscus to fall from the upper timing mark to the lower timing mark is measured using a stopwatch. Repeat measurements are typically taken and averaged to ensure accuracy. The viskometer constant is determined by calibrating the viskometer with liquids of known viscosity at specific temperatures. This instrument is widely used in various industries, including petroleum, chemical, and food processing.