Amagat Explained

An amagat (denoted amg or Am^[1]) is a practical unit of volumetric number density. Although it can be applied to any substance at any conditions, it is defined as the number of ideal gas molecules per unit volume at 1 atm (101.325 kPa) and 0 °C (273.15 K). It is named after Émile Amagat, who also has Amagat's law named after him.

SI conversion

The amg unit for number density can be converted to the SI unit of moles per cubic meter (mol/m³) by the formula$$1\backslash \; \backslash text\; \backslash overset\; \backslash \; \backslash frac\; \backslash text^3\; \backslash approx\; 44.615\; \backslash text^3,$$where

≘ indicates correspondence, since the SI unit is of molar concentration and not number density;

is the Loschmidt number;

is the Avogadro constant.

The number density of an ideal gas at absolute pressure and absolute temperature can be calculated as$$\backslash eta\; =\; \backslash frac\; \backslash \; \backslash frac\; \backslash \; \backslash text,$$where  = 273.15 K, and  = 101.325 kPa (STP before 1982).

Example

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

Notes and References

1. Methane and ammonia abundance in the atmosphere of Saturn. V. G. Teifel. 1976. Sov. Astron. Lett.. 2. 6. 232. 1976SvAL....2..232T.