Mass fraction ( $w_{i} = m_{i} / \sum_{j} m_{j}$ )

The mass fraction of component

i

in a mixture is

w_{i} = m_{i} / \sum_{j} m_{j}

. It is dimensionless, lies between zero and one, and the component mass fractions sum to one when all material is included.

For example, a mixture containing

5

grams of solute and

95

grams of solvent has solute mass fraction

0.05

, or five percent by mass. This differs from a mole fraction, which counts amounts of substance, and from a mass-per-volume concentration. A temperature-dependent volume change does not by itself change the mass fraction of a closed sample.

Table of contents
- Mass percentage Mass fraction
- Mass mixing ratio Mass fraction

Mass percentage ( $100 w_{i} %$ )

 0  0

The mass fraction multiplied by 100%.

Mass mixing ratio ( $q = ρ_{a} / ρ$ )

 0  0

The mass mixing ratio used in a dilute radiative transfer model is absorber mass density divided by total atmospheric mass density. A hydrostatic pressure interval contributes absorber mass path

q d p / g

. Some meteorological conventions divide by dry-air mass instead; the convention must be stated. A volume or mole mixing ratio instead contributes absorber moles