terminology - How to distinguish mass concentration and density?

I am writing a proof where I have to mention both with density and of a material and mass concentration (mass/volume) of a material.

I am using the letter $\rho$ to represent density, and I didn't want to abuse the same symbol for concentration because it will make the whole proof much harder to follow. I would also prefer to avoid subscripts as the only distinguishable element.

What other symbol or syntax should I use to distinguish density from mass concentration of a material?

Answer

According to IUPAC's Green Book [1], both $γ$ and $ρ$ can be employed to denote mass concentration. Fragment of a table from the section 2.10 GENERAL CHEMISTRY [1, p. 48]:

$$ \begin{array}{llll} \hline \text{Name} & \text{Symbol} & \text{Definition} & \text{SI unit} \\ \hline \ldots \\ \text{mass concentration, (mass density)} & γ, ρ & γ_\ce{B} = m_\ce{B}/V & \pu{kg m-3} \\ \ldots \\ \hline \end{array} $$

[…] In polymer science the word “concentration” and the symbol $c$ is normally used for mass concentration.

Also, from the SI Brochure, [2, p. 139]:

$$ \begin{array}{lll} \hline \text{Derived quantity} & \text{Typical symbol} & \text{Derived unit expressed} \\ & \text{of quantity} & \text{in terms of base units} \\ \hline \ldots \\ \text{mass concentration} & γ, ρ & \pu{kg m-3} \\ \ldots \\ \hline \end{array} $$

References

1. IUPAC “Green Book” Quantities, Units, and Symbols in Physical Chemistry, 3rd ed.; Cohen, R. E., Mills, I., Eds.; IUPAC Recommendations; RSC Pub: Cambridge, UK, 2007. ISBN 978-0-85404-433-7.


2. BIPM. Le Système International d’unitès / The International System of Units (“The SI Brochure”), 9th ed.; Bureau international des poids et mesures: Sèvres, 2019.