ASTM D1957 Standard Test Method for Hydroxyl Value of Fatty Oils and Acids
3. Significance and Use
3.1 Hydroxyl value is important in establishing reactivity with acids and isocyanates. It is also a measure of the degree of dehydration of castor oil.
3.2 This test method determines the total amount of residual hydroxyl groups present in oils and other fatty acid-containing materials, reported as hydroxyl value.
3.3 This test method involves the acetylation of hydroxyl-containing fatty oils and acids using pyridine as solvent. Other groups that will react with acetic anhydride such as primary and secondary amines under the conditions of the method will be reported as hydroxyl. The hydroxyl value is expressed as milligrams of potassium hydroxide equivalent to the hydroxyl content of 1 g of the oil. A correction is applied for acid groups present.
