The reaction of picric acid with epoxides I. A colorimetric method

A colorimetric method has been developed for the analysis of epoxides by reaction with picric acid. Picric acid was found to be the best of several acidic chromophores in its reaction with epoxides. Despite a nonquantitative reaction, the product concentration is proportional to the original concentration, i.e., it follows Beer’s Law. The reaction variables were studied with methyl mono- and diepoxystearates, epoxidized cottonseed oil andVernonia anthelmintica oil. The general applicability of the method was demonstrated by reaction with butyl epoxystearate, styrene oxide, a number of 3-substituted propylene oxides and two commercial epoxy resins. Presented in part at the First World Fat Congress, Hamburg, Germany, in October, 1964, and at the AOCS Meeting in Houston, Texas, April 1965.