<P> Saponification value (or "saponification number" / "Koettstorfer number", also referred to as "sap" for short) represents the number of milligrams of potassium hydroxide required to saponify 1g of fat under the conditions specified . It is a measure of the average molecular weight (or chain length) of all the fatty acids present . As most of the mass of a fat / tri-ester is in the 3 fatty acids, it allows for comparison of the average fatty acid chain length . The long chain fatty acids found in fats have a low saponification value because they have a relatively fewer number of carboxylic functional groups per unit mass of the fat as compared to short chain fatty acids . If more moles of base are required to saponify N grams of fat then there are more moles of the fat and the chain lengths are relatively small, given the following relation: </P> <P> Number of moles = mass of oil / average molecular mass </P> <P> The calculated molar mass is not applicable to fats and oils containing high amounts of unsaponifiable material, free fatty acids (> 0.1%), or mono - and diacylglycerols (> 0.1%). </P>

Relevance of determination of saponification number for lubricating oils