Semimicro determination of the neutralization equivalents of higher fatty acids by non-aqueous titrations

Summary

The neutralization equivalents of higher fatty acids can be determined on a semi-micro scale by titration of the acids in a non-aqueous medium (methanol and benzene) with potassium methoxide using a mixture of 0.4% methanolic solutions of phenol red, cresol red and bromothymol blue in the ratio of 3∶1∶1 as indicator. If the strength of the potassium methoxide used is less than 0.02 N, better results are obtained by dissolving the weighed amount of the acid in a known volume of potassium methoxide and back titrating the excess with standard oxalic acid solution in the same solvent because the colour change at the end point is sharper from alkaline to the acid medium.