II.

Properties and Occurrence

Fluorine is a pale, greenish-yellow gas, slightly heavier than air, poisonous, corrosive, and of penetrating and disagreeable odor. Its atomic weight is 18.998. Fluorine melts at -219.61°C (-363.30°F), boils at -188.13°C (-306.63°F), and has a specific gravity of 1.51 in its liquid state at its boiling point. It is the most chemically active of the nonmetallic elements. It combines directly with most elements and indirectly with nitrogen, chlorine, and oxygen. Nearly all compounds are decomposed by fluorine to form fluorides that are among the most stable of all chemical compounds.

Fluorine occurs naturally in the combined form as fluorite, cryolite, and apatite. Fluorite is the source of most fluorine compounds. Fluorine also occurs as fluorides in seawater, rivers, and mineral springs, in the stems of certain grasses, and in the bones and teeth of animals. It is the 17th element in order of abundance in Earth’s crust.

The preparation of fluorine as a free element is difficult and seldom done, since free fluorine is very reactive. However, gaseous fluorine can be prepared by electrolytic techniques, and liquid fluorine may be prepared by passing the gas through a metal or rubber tube surrounded by liquid air.