ABSOLUTE MEASUREMENT OF THE DENSITY OF WATER IN THE RANGE 0-85°C AND 0.101325 MPA

The absolute density of water was redetermined in a temperature range of 0-85 °C and at a pressure of 0.101325 MPa for pure water having an isotopic composition of Standard Mean Ocean Water (SMOW). The measurement is independent of any density measurements made in the past. The absolute density of SMOW was measured at 16 °C by hydrostatic weighing of three fused quartz spheres in 18 water samples, and found to be 998.9468 kg/m³ with a combined standard uncertainty of 0.0007 kg/m³. The thermal expansion in an extended range 0-85 °C was measured separately by a dilatometric method. The results of the measurements were used to produce the following equation for the absolute density of water as a function of temperature.