Density of water by M. Tanaka
The density of water is very important due to its use in various fields of science and industry, including equipment calibration. This calculator is based on the method published by M. Tanaka in 2001, and is described for temperatures from (0 to 40) °C, the work was approved by the CIPM (International Committee of Weights and Measures) the relative standard uncertainty used for the formula is of the order of 1x10-5.
M. Tanaka's formula is modified to omit corrections for dissolved air and liquid compressibility, likewise the constant a5 is given for tap water, if another type of water is required the isotopic abundance must be calculated, this is the proportion or percentage in which the different isotopes of a chemical element are found in nature, in this case water, which can vary for different types of water, such as seawater, drinking water, distilled water, etc.
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Water density table by temperature
4 °C = 999.9749 kg/m³
10 °C = 999.7027 kg/m³
15 °C = 999.1026 kg/m³
20 °C = 998.2067 kg/m³
25 °C = 997.0470 kg/m³
30 °C = 995.6488 kg/m³
40 °C = 992.2152 kg/m³
How is it used in metrology?
It is the basis of gravimetric calibration of volumetric equipment (pipettes, burettes, flasks and gravimetric flow meters): volume is obtained by dividing the mass of water by its density at the measured temperature. A 1 °C temperature error is about 0.02 % in volume at 20 °C.
Frequently asked questions
Should I correct for dissolved air?
Yes, for high-accuracy work: air-saturated water is about 0.0025 kg/m³ less dense between 0 and 25 °C.
And for pressure?
Water compresses about 0.046 kg/m³ for every 100 kPa above standard atmospheric pressure.
Why is maximum density near 4 °C?
Because of hydrogen bonding: below 3.98 °C water starts arranging into a more open structure and its density drops.