Abstract
A measurement of the thermal dilatation of pure water has been made by detecting the change of buoyancy acting on a cylindrical hollow artifact made of fused quartz immersed in water between the temperatures of 0 °C and 44 °C. The formula for the thermal dilatation of water, free from air, is obtained in terms of the relative density ρ/ρ0 at the pressure of 101 325 Pa with an uncertainty of less than 1 ppm is as follows:
ρ/ρ0 = 0,999 867 75 + 6,786 687 54 × 10-5(t/°C) - 9,090 991 73 × 10-6(t/°C)2 + 1,025 981 51 × 10-7(t/°C)3 - 1,350 290 42 × 10-9(t/°C)4 + 1,326 743 92 × 10-11(t/°C)5 - 6,461 418 × 10-14(t/°C)6
where the temperature of the maximum density ρ0 is 3,983 4 °C in terms of the ITS-90. The uncertainty of the measurement and the derived formula is evaluated to be 0,2 to 0,5 ppm in standard deviation for the same temperature range.