Accession Number : ADD095122

Title :   Viscosity of Liquid Water in the Range - 8 C to 150 C,

Corporate Author : NATIONAL STANDARD REFERENCE DATA SYSTEM

Personal Author(s) : Kestin, Joseph ; Sokolov, Mordechai ; Wakeham, William A

Report Date : Jan 1978

Pagination or Media Count : 13

Abstract : This paper re-analyzes the results of earlier, very precise measurements of the viscosity of water at essentially atmospheric pressure. This is done in terms of a new, theoretically-based equation for the operation of a capillary viscometer rather than in terms of semi-empirical equations used by the original authors. The new analysis eliminates possible systematic errors and permits the establishment of realistic error bounds for water in its role as a standard reference substance for viscosity. The latter are smaller than those embodied in the most recent International Formulation. Standard values of the ratio of viscosity at a temperature T to its value of 20 deg C have been derived from the re-analyzed data because the uncertainty of this ratio is an order of magnitude smaller than that of the absolute values. The ratios are used to generate absolute values with the aid of the standard NBS datum microns = 1002.0 microns Pa s at 20 C. The viscosity ratios have been correlated with the aid of two empirical equations. The more accurate equation covers the range 0 deg C less than or equal to tau less than or equal to 40 deg C with an uncertainty of plus or minus 0.05%. The less accurate equation covers the wider range -8 deg C less than or equal to tau less than or equal 150 deg C with the more limited accuracy of plus or minus 0.2%. The two empirical equations are compatible with each other to 0.09%. (Author)

Descriptors :   *WATER, *VISCOSITY, LIQUIDS, VISCOSIMETERS, MEASUREMENT, STANDARDS, VALUE, RATIOS, TEMPERATURE, PRESSURE, EQUATIONS, EXPERIMENTAL DATA

Subject Categories : Physical Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE