Summary of Requirements for Data Tables
1) Uncertainties[1], [2] must be included for all variables, constraints, and properties
a. The standard uncertainty u must be included for all variables and constraints
i. For all phase equilibrium results (VLE, LLE, SLE, etc.), only standard uncertainties are reported for all state variables
ii. The relative standard uncertainty ur can also be used.
1. ur(x) = u(x)/|x| for x ≠ 0
b. The combined expanded uncertainty U with level of confidence 0.95 (k = 2) for all properties, such as densities, viscosities, heat capacities, speeds of sound, triple point temperatures, excess enthalpies, etc.
c. The symbol % should not be used in the expression of uncertainty.
i. Use “u(p) = 0.01∙p” or “ur(p) = 0.01”, rather than “The uncertainty for the pressure p was 1 %.”
ii. Use of % in the specification of uncertainties for compositions has led to much ambiguity in the literature. For example, the phrase “the gas phase compositions y were determined to 2 %” can have multiple interpretations (i.e., Does 2 % uncertainty mean u(y) = 0.02 or 0.02∙y?).
2) Phases present must be identified clearly
a. The phase of all property values must be identified.
b. Notation for phase equilibrium results should be in accord with IUPAC recommendations. [3], [4]
3) Compositions must be defined completely
a. All molalities m must include the definition of the solvent.
b. Molarity should not be used for composition specification.
4) Mixing of experimental and derived data in the same table is discouraged
a. If they are mixed, footnotes should be used to clearly specify the derived values.
[1] Guide to the Expression of Uncertainty in Measurement, ISO, October, 1993. This guide (commonly called GUM) was published by ISO in the name of BIPM, IEC, IFCC, ISO, IUPAC, IUPAP, and OIML.
[2] The recommendations have been succinctly presented in Chirico et al. J. Chem. Eng. Data 2003, 48, 1344-1359 and Guidelines for the Evaluation and Expression of Uncertainty in NIST Measurement Results, NIST Technical Note 1297; Taylor, B. N.; Kuyatt, C. E.; NIST: 1994 (http://physics.nist.gov/cuu/).
[3] IUPAC Physical and Biophysical Chemistry Division. Quantities, Units, and Symbols in Physical Chemistry, 3rd ed. (The Green Book). Prepared for publication by Cohen, E.R.; Cvitaš, T.; Frey, J.G.; Holmström, B.; Kuchitsu, K.; Marquardt, R.; Mills, I.; Pavese, F.; Quack, M.; Stohner, J.; Strauss, H.L.; Takami, M.; Thor, A.J. The Royal Society of Chemistry: Cambridge, U.K., 2007.
[4] Bolz, A.; Deiters, U. K.; Peters, C. J.; de Loos, T. W., Nomenclature for phase diagrams with particular reference to vapor-liquid and liquid-liquid equilibria. Pure Appl. Chem. 1998, 70(11), 2233-2257.