The activity
coefficient 
of a substance B in a liquid or solid mixture containing
mole fractions
,
, ... of the substances B, C, ... is a dimensionless quantity defined in terms of the
chemical potential 
of B in the mixture by:
where
denotes the set of
mole fractions
,
, ... . The activity
coefficient 
of a solute B in a solution (especially a dilute liquid solution) containing molalities
,
, ... of solutes B, C, ... in a solvent A is a dimensionless quantity defined in terms of the
chemical potential 
by:
Source:
PAC, 1994, 66, 533
(Standard quantities in chemical thermodynamics. Fugacities, activities and equilibrium constants for pure and mixed phases (IUPAC Recommendations 1994))
on page 543
PAC, 1994, 66, 533
(Standard quantities in chemical thermodynamics. Fugacities, activities and equilibrium constants for pure and mixed phases (IUPAC Recommendations 1994))
on page 546
PAC, 1990, 62, 2167
(Glossary of atmospheric chemistry terms (Recommendations 1990))
on page 2171
PAC, 1996, 68, 957
(Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996))
on page 960
Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A.Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8.
doi:10.1351/goldbook.
, 
of a radioactive material
