The "Mass Concentration" of substance B is defined as the mass of a constituent divided by the volume of the mixture .
Applicable units are those of quantitykind:MassConcentration
http://en.wikipedia.org/wiki/Mass_concentration_(chemistry)
The "Mass Concentration" of substance B is defined as the mass of a constituent divided by the volume of the mixture .
$\rho_B = \frac{m_B}{V}$, where $m_B$ is the mass of substance $B$ and $V$ is the volume.
http://www.iso.org/iso/catalogue_detail?csnumber=31894