Amagat

The amg unit for number density can be converted to the SI unit mol/m³ by the formula

${\displaystyle 1\ {\text{amg}}\ {\overset {\frown }{=}}\ 44.615\ {\text{mol}}/{\text{m}}^{3},}$

where ≘ indicates correspondence, since the SI unit is of molar concentration and not number density. The conversion factor (44.615...) is called the Loschmidt number.

The number density of an ideal gas at pressure p and temperature T can be calculated as[3]

${\displaystyle \eta =\left({\frac {p}{p_{0}}}\right)\left({\frac {T_{0}}{T}}\right)\ {\text{amg}},}$

where T₀ = 273.15 K, and p₀ = 101.325 kPa (STP before 1982).

Number density of an ideal gas (such as air) at room temperature (20 °C) and 1 atm (101.325 kPa) is

${\displaystyle \eta =\left({\frac {1\ {\text{atm}}}{p_{0}}}\right)\left({\frac {273.15\ {\text{K}}}{(273.15+20)\ {\text{K}}}}\right)\ {\text{amg}}=0.932\ {\text{amg}}.}$