# What is a unit of pressure exactly equivalent to one mmHg?

Jul 20, 2017

This would be the color(blue)("torr".

#### Explanation:

It is conventional to know the basic units of pressure and be able to interconvert between them. The "$\text{torr}$" is named after the Italian physicist sfcolor(red)("Evangelista Torricelli", who invented the barometer in 1643.

Here are the pressure conversions worth knowing:

$1$ $\text{atm}$ $= 760$ $\text{mm Hg}$ $= 760$ $\text{torr}$ $= 1.01325$ $\text{bar}$ $= 101.325$ $\text{kPa}$ $= 101325$ $\text{Pa}$ $= 14.7$ $\text{psi}$

Jul 21, 2017

How about $\frac{1}{760} \cdot a t m$?

#### Explanation:

We know that $1 \cdot a t m$ will support a column of mercury that is $760 \cdot m m$ high. A mercury column is thus a good visual gauge for pressures at $1 \cdot a t m$, or pressures below $1 \cdot a t m$.

You raise or try to raise the mercury column over $760 \cdot m m$ you will probably get mercury all over the laboratory or the classroom. You can convert this to (preferably for chemists) $\text{atmospheres}$, or $\text{kilopascals}$, or even $\text{pounds per square inch}$, knowing the relationship between $\text{atmospheres}$ and the other units. You do not use $m m \cdot H g$ for pressure OVER atmospheric.