This explains the usage of ρ (the lower case Greek letter rho), the symbol most often used for density.
Mass concentration depends on the variation of the volume of the solution due mainly to thermal expansion.
In biology and medicine, the "%" symbol is widely used in a misnomer sense to denote mass concentration, also called "mass/volume percentage".
The common names of intravenous sugar solutions, such as D5W and D50W, reflect this convention.
This approximation breaks down as the solute concentration is increased (for example, in water–NaCl mixtures).
An extreme example is saturated solution of potassium iodide (SSKI) which attains 100 "%" m/v potassium iodide mass concentration (1 gram KI per 1 mL solution) only because the solubility of the dense salt KI is extremely high in water, and the resulting solution is very dense (1.72 times as dense as water).
For binary mixtures, the conversion to molality bi is given by: The values of (mass and molar) concentration different in space triggers the phenomenon of diffusion.