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In physical chemistry experiments, viscosity is measured by means of several methods and with several apparatus. However, high cost has hampered large-scale use of viscometers in undergraduate physical chemistry experiments. Commercially available viscometers are expensive and also pose a number of difficulties, such as the large volume of the solvent needed for cleaning and the need for the same volume of the liquid for each run. Further, various models of rotational viscometers are recommended for high-, medium-, and low-viscosity applications. Selecting the right model will ensure maximum sensitivity and accuracy in the range of viscosities to be measured. This refers not only to the calibration of the viscometer, but also to elucidating the raw data, knowing the limitations of the sensing geometry. Because all sensing geometries have limitations, the condition for flow measurement should be closely scrutinized.
Here we describe a simple, low-cost rotational viscometer (the figure) constructed with two dc motors, a rotor, measuring cup (usually a beaker), and millivolt recorder, which was well-suited for measuring viscosity. (figure omitted) It has potential advantages over existing viscometers because it is easily used for comparative measurement....