White Paper

Calculated pH Based on Conductivity

White Paper

Deriving CO₂ and pH from Conductivity Values for Power Plant Cycle Chemistry

This white paper discusses how power plants can derive a calculated pH value and a calculated CO2 value from measurements of specific,cation and degassed cation conductivity. These important calculated values can be transmitted via a multi-parameter transmitter for managing and validating a power plant's water cycle chemistry measurements.

The white paper covers both the underlying scientific principles that allow for the generation of a calculated pH value and a calculated CO2 value, based on the three measured conductivity values, and then explains how this is achieved quickly and directly in a multi-parameter transmitter.


The concept and practice of generating a calculated pH value, calculated carbon dioxide value and calculated anion concentrations from conductivity measurements has been available for a number of years, but in the past it required separate computer diagnostic systems. As analytical technology has continued to advance, multi-parameter transmitters offer a mix-and-match flexibility to power plants to analyze up to 11 parameters for monitoring needs at any given measurement location.

First, the white paper introduces the concept of generating calculated pH and other critical cycle chemistry measurements. It offers that in cycle chemistry samples, deriving a calculated pH measurement can sometimes be more accurate and reliable than the measurement from a standard glass pH electrode. Having both a measurement point and a calculated pH value can support validation in your water system measurements.

Before moving into the science behind calculated pH, calculated CO2 and calculated anion concentrations, the white paper covers how power plants collect and use analytical data in the modern context of cost constraints and decreasing personnel.

The white paper then provides the sound scientific background behind calculated pH and its relationship with conductivity. It also assesses the requirement to have properly specified conductivity sensors to provide accurate, reliable measurement from which calculated pH can be derived. 

It then moves on to the topic of generating a calculated carbon dioxide value from specific, cation and degassed cation conductivity measurements, and anion concentration in degassed cation conductivity samples. 

Finally, the white paper covers the role multi-parameter transmitters play in determining and displaying calculated pH, calculated CO2 and calculated anion concentrations.