Saponification value determination of difficultly saponifiable drying oil products

Conclusions The use of n‐butyl alcohol as a solvent for saponification of a representative series of drying oils has been studied. It appears from this work that n‐butyl alcoholic potassium hydroxide reagent, containing 5% of water added to the reaction mixture, gives very acceptable results based upon calculated saponification values. With the exception of maleic‐modified oils of certain types, the solvent system of ethyl alcohol‐pyridine exhibits excellent results based upon calculated values. However it has the disadvantages that it is a two‐solvent system, and the pyridine must be of reagent grade to avoid end‐point difficulties. The end‐point in the butyl alcohol system is not as sharp as the normal saponification end‐point in ethyl alcohol. This may be caused by the two‐phase nature of the titration mixture. Addition of ethyl alcohol to the n‐butyl alcoholic saponification reaction mixture gives improvement, although the end‐point is not as sharp as in the regular ethyl alcohol system. Work is continuing on methods for improvement of the end‐point.