Uncertainty Reporting for Experimental Thermodynamic Properties

Abstract

This paper reviews practices in the expression of uncertainty in the experimental literature for thermodynamic property measurements with determinations of critical temperature for pure compounds used as a case study. The time period considered is from 1940 to the present, with an emphasis on results published since 1990. One hundred ninety-four articles were considered involving hundreds of compounds. The goals of this paper are to show how the nature and extent of estimations of uncertainty have changed in this time period and to document the extent to which the information provided in the articles corresponds to the recommendations of the GUM. (The GUM is the Guide to the Expression of Uncertainty in Measurement published in 1993 by the International Organization for Standardization, ISO. This document describes current recommended practices in this area.) It is shown that although gradual and continuous progress has been made in the reporting of uncertainty information, comprehensive uncertainty analyses remain rare, particularly with regard to the consideration of contributions arising from sample impurities. Problems in the application of experimental property results to technological challenges are discussed within the broad context of inconsistencies in the expression of uncertainty. Widespread acceptance and application of the standard methods and terminologies established within the GUM are encouraged for the benefit of experimentalists, data evaluators, and data users alike.