Cryogenic fluids, density reference system : provisional accuracy statement /

The density reference system of the Cryogenics Division of the National Bureau of Standards is described. This system is used in making density measurements of cryogenic liquids. The methods of computation and the accuracy to which the density of the liquid can be measured are discussed in detail. At this time the estimate of sample standard deviation for a single density measurement made using this system is 0.016% (at 422.63 kg/cu m). Using three times this standard deviation as a limit for random error and using 0.028% as the bound for known sources of possible systematic error, the uncertainty of a single determination with this system is + or - 0.076%. This statement of accuracy applies for the density range 400 to 480 kg/cu m, pressures from 0 to 3 bar, and temperatures from 110 K to 125 K. Because of the densimeter design, this accuracy statement is expected to apply to the density range from 400 to 1000 kg/cu m and to the temperature range of 77 to 300 K at least, and to pressures of 7 bar, though these ranges of application have yet to be verified.Issued November 1977.Prepared for the American Gas Association, Inc., by Cryogenic Division, and Applied Mathematics Division, of Institute for Basic Standards of NBS.Includes bibliographical references.The density reference system of the Cryogenics Division of the National Bureau of Standards is described. This system is used in making density measurements of cryogenic liquids. The methods of computation and the accuracy to which the density of the liquid can be measured are discussed in detail. At this time the estimate of sample standard deviation for a single density measurement made using this system is 0.016% (at 422.63 kg/cu m). Using three times this standard deviation as a limit for random error and using 0.028% as the bound for known sources of possible systematic error, the uncertainty of a single determination with this system is + or - 0.076%. This statement of accuracy applies for the density range 400 to 480 kg/cu m, pressures from 0 to 3 bar, and temperatures from 110 K to 125 K. Because of the densimeter design, this accuracy statement is expected to apply to the density range from 400 to 1000 kg/cu m and to the temperature range of 77 to 300 K at least, and to pressures of 7 bar, though these ranges of application have yet to be verified.Mode of access: Internet