An amagat is a practical unit of volumetric
number density
The number density (symbol: ''n'' or ''ρ''N) is an intensive quantity used to describe the degree of concentration of countable objects (particles, molecules, phonons, cells, galaxies, etc.) in physical space: three-dimensional volumetric number ...
. Although it can be applied to any substance at any conditions, it is defined as the number of
ideal gas molecule
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioch ...
s per unit volume at 1
atm (101.325
kPa
KPA may refer to:
* Keele Postgraduate Association, Keele University, UK, formerly Keele Research Association (KRA)
* Kensington (Olympia) station, London, England, National Rail station code
* Kenya Ports Authority
* ''Kiln phosphoric acid'', a d ...
) and 0
°C
The degree Celsius is the unit of temperature on the Celsius scale (originally known as the centigrade scale outside Sweden), one of two temperature scales used in the International System of Units (SI), the other being the Kelvin scale. The ...
(273.15 K).
[
] It is named after
Émile Amagat, who also has
Amagat's law
Amagat's law or the Law of Partial Volumes describes the behaviour and properties of mixtures of ideal (as well as some cases of non-ideal) gases. It is of use in chemistry and thermodynamics. It is named after Emile Amagat.
Overview
Amagat's la ...
named after him. The abbreviated form of amagat is "amg". The abbreviation "Am" has also been used.
SI Conversion
The amg unit for number density can be converted to the SI unit mol/m
3 by the formula:
:
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
[In this formula, absolute units of pressure and temperature, relative to ]vacuum
A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often dis ...
and absolute zero
Absolute zero is the lowest limit of the thermodynamic temperature scale, a state at which the enthalpy and entropy of a cooled ideal gas reach their minimum value, taken as zero kelvin. The fundamental particles of nature have minimum vibration ...
, must be used.
:
,
where ''T''
0 = 273.15
K and ''p''
0 = 101.325
kPa
KPA may refer to:
* Keele Postgraduate Association, Keele University, UK, formerly Keele Research Association (KRA)
* Kensington (Olympia) station, London, England, National Rail station code
* Kenya Ports Authority
* ''Kiln phosphoric acid'', a d ...
(
STP before 1982).
Example
Number density of an ideal gas (such as air) at
room temperature
Colloquially, "room temperature" is a range of air temperatures that most people prefer for indoor settings. It feels comfortable to a person when they are wearing typical indoor clothing. Human comfort can extend beyond this range depending on ...
(20
°C
The degree Celsius is the unit of temperature on the Celsius scale (originally known as the centigrade scale outside Sweden), one of two temperature scales used in the International System of Units (SI), the other being the Kelvin scale. The ...
) and 1 atm (101.325 kPa) is
:
References
{{reflist
Amount of substance
Units of density
Physical chemistry