Microdetermination of fluorine in organic compounds with modified type combustion flask

Abstract

An improved combustion flask into which was introduced washing liquid by the reduced pressure to absorb combustion products was used for rapid determination of organic fluorine by titration with thorium nitrate solution (0.01N) using methylthymolblue as an indicator. The washing buffer solution of pH 3.43.5 was prepared by 0.1%. sodium acetate and 10% acetic acid, and the combustion aids were filter paper and gelatin capsule. The flask was heated in warm water just before combustion and cooled in ice water for 1 min. after combustion. Extremely reduced pressure thus obtained enabled only 10 ml of the washing liquid to absorb combussion product effectively and clean up the wall of flask. The solution in the flask was less voluminous than that in conventional procedure, and hence the indicator showed distinctive end point which gave more sensitive results. Only 56 min. was needed for an analysis.