| ratio of the product of ion molality b and a correction factor γ to the molality b° of the same ion in a standard solution under standardized conditions
a = bγ / b°
Note 1 to entry: The correction factor is called activity coefficient and it is determined experimentally.
Note 2 to entry: Normally a standard solution is a solution of the ion at a molality of 1 mol/kg (exactly). Standardized conditions are normally 1 013,25 hPa and 25 °C.
Note 3 to entry: This entry was numbered 111-15-26 in IEC 60050-111:1996. It has been modified.