Principles of pH

pH has become a unit of measure so commonplace that it is now even referred to in consumer household products such as cosmetics, shampoo, 
and even food / beverage.  It is important to ask - what are we actually measuring when we refer to pH?

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pH has become a unit of measure so commonplace that it is now even referred to in consumer household products such as cosmetics, shampoo, and even food / beverage. It is important to ask - what are we actually measuring when we refer to pH?

This group of articles serves as a primer for the non-chemist to understand the basis for pH measurement. The first two topics provide an overview of the pH scale and the Nernst Equation that relates the sensor’s output signal to the pH value. The second two articles dive into the chemistry of ions in liquid (specifically the hydrogen ion) as well as the definitions of well-known liquids such as acids, bases, and salts.

pH test strips beside a reference color chart numbered 1–14, ranging from red (acidic) to purple (alkaline)
Understanding the pH scale is the first step to understanding the basic theory of how pH measurement works. This article discusses the concept of hydrogen ion concentration and how it relates to the pH measurement scale.
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The pH Scale
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The Nernst Equation
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Ions and Dissociation
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Acids, Bases, and Salts