Capillary viscometers

Abstract

Glass capillary viscometers may be categorised in three groups. These are: (1) Oswald type in its various modified forms for transparent liquids; (2) Suspended level type in which capillary is always full, which ensures a uniform pressure head independent of the volume of the liquid charged into the viscometer and (3) Reverse flow type in which liquid moves from capillary to measuring bulb and therefore suitable for use for opaque liquids. Each category has number of sets of viscometers named after the names of inventors. Modified Ostwald and Suspended Level categories, each has seven types of viscometers covering a range 0.2–20,000 mm2/s and 0.3–100,000 mm2/s respectively. Reverse flow type have 4 sets of viscometers. The covering range goes up to 300,000 m2/s. Importance of capillary viscometers is a very good repeatability. Hence are used to measure the viscosity of reference standard oils. Details of each type of viscometers have been discussed in this chapter.