Heats of Formation of Gaseous Fluoro- and Fluorochloro-Carbons

Abstract

THE heat of formation of carbon tetrafluoride was determined by von Wartenberg¹ by measurement of the heat of combustion of potassium in the gas to form potassium fluoride and carbon. We have repeated his work and made similar measurements for several other fully halogenated fluoro-compounds, for which previous experimental determinations were lacking. The general technique used was the same as that of von Wartenberg—in particular, the reaction chamber was of the same size and design as his, and the reaction was likewise initiated by striking a d.c. arc between a graphite rod and a quantity of potassium, filtered from oxide, contained in a nickel crucible. The ignition energy was, however, measured more reliably by recording the arc current and voltage simultaneously on a moving film by means of a double-beam oscillograph. The calorimeter was of the isothermally jacketed type, with kerosene as the calorimetric fluid, the heat capacity being determined electrically.