Modern commercial production methods are essentially variations on the procedures first used by Moisson. Fluorine is about one and one-third times, as heavy as air. Fluorine is the most electronegative and reactive of all elements. With the exception of some of the inert gases, fluorine reacts violently with metals and forms compounds with all elements including organic and inorganic substances. A stream of hydrogen ignites instantly when in contact with fluorine forming hydrogen fluoride.
Fluorine reacts vigorously with water liberating oxygen as ozone and forming hydrogen fluoride.
Finely divided metals, glass, ceramics, carbon, and water burn in fluorine with a bright flame. In much of this century it was also used in aerosol propellants. Sodium Fluoride is used as a prophylaxis against dental caries based on the observation that in sections of the country where drinking water contains small amounts of naturally occuring fluoride, children develop fewer cavities. Elemental fluorine is being studied as a rocket propellant as it has an exceptionally high specific impulse value. Compounds of fluorine with rare gases have now been confirmed.