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Many of the viscometers described in 19911 have remained in common use and have neither seen nor needed very much development. However, this chapter reviews the most significant developments in the field of viscometry in the last twenty years. First, the vibrating-wire viscometer is described. It has been significantly developed as an absolute instrument by virtue of new technologies and it is now a primary absolute instrument in some forms and an industrial tool for in situ measurment in other forms. Falling body viscometry is one of the oldest forms of measurement and the development of an instrument that satisfies the requisite constrainst of theory is set out in Section 4.2 and enables very accurate measurments for the first time. In Section 4.3 the adapatation of the rolling ball viscometer to operation in a diamond anvil cell allows viscometry up to pressures of 10 GPa for the first time. The chapter then concludes with two examples of improvements to capillary viscometry. In Section 4.4 the very careful use of capillary viscometry leads to the most precise measrements of the ratio of viscosities of gases. In Section 4.5 the use of sealed gravitational viscometers for the meassurment of the viscosity of volatile liquids is reviewed so as to explain past discrepancies in viscometric work on such fluids and provide a guide to correct operation.

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19 May 2014
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