Experimental results from four recent research reports on the determination of the density/temperature relationship of Standard Mean Ocean Water (SMOW) under a pressure of 101 325 Pa are analysed and a new formula is recommended for metrological applications. This paper determines the formulae of density and relative density, with their uncertainties, in the temperature range 0 °C to 40 °C. The uncertainty estimation of one of the reports included in the analysis has been re-evaluated. Effects on water density due to isotopic mixtures other than SMOW, ambient pressures different from 101 325 Pa, and the presence of dissolved air, are also reviewed.
Attention is drawn on the fact that several tables of the thermal expansion of water are available between 0 and 40 °C. For a given temperature, the values they give are somewhat different. No criterion helps to select between them the table that gives the most reliable values. The drawbacks of such a situation are reviewed and recommendations made to lessen their effects.Tables and graphs show the existing deviations, according to temperature, between the values of the various tables.New observations are needed to obtain values of the thermal expansion of water between 0 and 40 °C, having a relative accuracy of at least 1 × 10-6.
Variation of the Water Denaity as a Function of its IsotopicCmposition In an article published in 1967 in this journal [l], an initial theoretical formula has been proposed to represent the variation of the water density as a function of the variations of its isotopic composition. Following this article, an experimental programme has been undertaken with the purpose of checking the validity of the formula. Limited a t first to a density interval of 2.10-3 kg.m-8, this study was then enlarged to a ten times greater interval. As a consequence, the formula has been revised, so that it is more suitable for this new interval of density.Experimental observations have been made on the density and the isotopic composition of various water samples. The variations of density have been determined by observing the buoyant force exerted by each sample of water on a stainless steel cylinder. The isotopic composition has been determined by mass spectrometry.The law of variation of the water density as a function of its isotopic composition, deduced from our observations, is slightly different from that obtained by the theoretical formula.
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