standard molality m ⦵, m °

Chosen value of molality and usually equal to 1 mol kg −1.
Source:
Green Book, 2nd ed., p. 54
See also:
PAC, 1994, 66, 533 (Standard quantities in chemical thermodynamics. Fugacities, activities and equilibrium constants for pure and mixed phases (IUPAC Recommendations 1994)) on page 538