In chemistry, acid number (or "neutralization number" or "acid value" or "acidity") is the mass of potassium hydroxide (KOH) in milligrams that is required to neutralise one gram of chemical substance. Thus, the acid number is a measure of the amount of carboxylic acid groups in a chemical compound.

In a typical procedure, a known amount of sample dissolved in organic solvent is titrated with a solution of potassium hydroxide with known concentration and with phenolphthalein as a colour indicator.

At Exova, we use standard methods for determining acid number, such as ASTM D 974 and DIN 51558 (for mineral oils, biodiesel).

For more information on how this test method can meet your specific requirements please contact us.