osmolality, m

https://dx.doi.org/10.1351/goldbook.O04340
Quotient of the negative natural logarithm of the rational activity of water and the molar mass of water.
Source:
PAC, 1996, 68, 957 (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 985