Interference of carbon dioxide, resulting from the schöniger flask combustion of organofluorine compounds, in the titrimetric determination of fluorine

Abstract

Carbon dioxide produced during the Schöniger flask combustion of organofluorine compounds has been found to interfere in the titrimetric determination of fluorine. When thorium nitrate that had been standardised against sodium fluoride solution was used, the fluorine content found was consistently 93 per cent. of theory. This interference was overcome by adding sodium carbonate to the solution used for standardisation before titration. For detection of the titration end-point, an improved indicator, methylthymol blue, was used.

By using this procedure, compounds containing between 4 and 30 per cent. of fluorine, either in a CF₃ or CF group, have been assayed satisfactorily. No interference from nitrogen, sulphur or chlorine contained in some of the compounds was observed.