IAPWS logo

IAPWS R11-07
Release on the Ionization Constant of H2O
August 2007

PDF of document

This formulation is recommended for the calculation of the ionization constant of ordinary water as a function of temperature and density. The range of validity is from 0 to 800 °C at densities up to 1.25 g m−3.
The development of the formulation and comparisons to available data are described in detail in a scientific article.

Online Calculation
The Russian National Committee of IAPWS (through Moscow Power Engineering Institute) has provided an online calculation page, which may be useful in program development and verification. Note that IAPWS is not responsible for the content of these online calculation pages.

Revision History

This Release is the product of the Working Groups "Thermophysical Properties of Water and Steam" (TPWS) and "Physical Chemistry of Aqueous Systems" (PCAS) of the International Association for the Properties of Water and Steam (IAPWS).

This page updated February 25, 2019

iapws.org >> releases, guidelines, etc. >> Release on Ionization Constant