2. Mercury density

The density of mercury depends primarily on its purity and isotopic composition. However, if we use mercury of sufficient purity, obtained by distillation and stored in airtight conditions, the resulting variations in density can be as little as 10 ^–6 in relative terms. Similarly, mercury is slightly compressible and its density therefore depends on the pressure to which it is subjected. However, this effect is only noticeable at high pressures, and can be completely neglected for the pressures considered (1 bar) with the degree of accuracy required.

On the other hand, variations in the density of mercury as a function of temperature are significant (of the order of 2 · 10 ^–4 per degree in relative terms) and therefore cannot be neglected. Measurements of mercury's density...