Note 49 — Chapter XI · THE HALOGENS: CHLORINE, BROMINE, IODINE, AND FLUORINE

According to Moissan, fluorine is disengaged by the action of an electric current on fused hydrogen potassium fluoride, KHF2. The present state of chemical knowledge is such that the knowledge of the properties of an element is much more general than the knowledge of the free element itself. It is useful and satisfactory to learn that even fluorine in the free state has not succeeded in eluding experiment and research, that the efforts to isolate it have been crowned with success, but the sum total of chemical data concerning fluorine as an element gains but little by this achievement. The gain will, however, be augmented if it be now possible to subject fluorine to a comparative study in relation to oxygen and chlorine. There is particular interest in the phenomena of the distribution of fluorine and oxygen, or fluorine and chlorine, competing under different conditions and relations. We may add that Moissan (1892) found that free fluorine decomposes H2S, HCl, HBr, CS2, and CNH with a flash; it does not act upon O2, N2, CO, and CO2; Mg, Al, Ag, and Ni, when heated, burn in it, as also do S, Se, P (forms PF5); it reacts upon H2 even in the dark, with the evolution of 366·00 units of heat. At a temperature of -95°, F2 still retains its gaseous state. Soot and carbon in general (but not the diamond) when heated in gaseous fluorine form fluoride of carbon, CF4 (Moissan, 1890); this compound is also formed at 300° by the double decomposition of CCl4 and AgF; it is a gas which liquefies at 10° under a pressure of 5 atmospheres. With an alcoholic solution of KHO, CF4 gives K2CO3, according to the equation CF4 + 6KHO = K2CO3 + 4KF + 3H2O. CF4 is not soluble in water, but it is easily soluble in CCl4 and alcohol.