Question

Why do we use a column of mercury rather than a column of water to measure pressure?

Answer 1

Consider the density of mercury versus that of water.

Explanation:

`rho_(Hg) = 13.55*g*mL^-1; rho_("water") = 1.00*g*mL^-1;`

One atmosphere will support a column of mercury `760` `mm` high. It would support a column of water approx. `10` `m` high. Sometimes, columns of water are used to measure osmotic pressures, which are much smaller than atmospheric pressures.