Hydroxyl value

In analytical chemistry, the hydroxyl value is defined as the number of milligrams of potassium hydroxide (KOH) required to neutralize the acetic acid taken up on acetylation of one gram of a chemical substance that contains free hydroxyl groups.

The acid value (AV) of the substance, determined in a separate experiment, enters into this equation as a correction factor in the calculation of the hydroxyl value (HV): Where HV is the hydroxyl value; VB is the amount (ml) potassium hydroxide solution required for the titration of the blank; Vacet is the amount (ml) of potassium hydroxide solution required for the titration of the acetylated sample; Wacet is the weight of the sample (in grams) used for acetylation; N is the normality of the titrant; 56.1 is the molecular weight of potassium hydroxide (g/mol); AV is a separately determined acid value of the chemical substance.

The content of free hydroxyl groups in a substance can also be determined by methods other than acetylation.

[1] Determinations of hydroxyl content by other methods may instead be expressed as a weight percentage (wt.

[2] The chemical substance may be a fat, oil, natural or synthetic ester, or other polyol.