Tuesday, 3 February 2015

Characteristics And Properties of Fluorine


Fluorine chemical element of atomic number 9, atomic weight 19.00 (he knows only one stable isotope, 199F). At room temperature is presented as a pale yellow gas, capable of liquefying only at very low temperature (-188 ° C at normal pressure). It is part of the group of the halogens, which constitutes the first member; is the most electronegative element, it shows a remarkable chemical reactivity and in fact is combined, directly or indirectly, with all elements (except with helium, argon and the neo) forming compounds, some of which are in turn equipped with easy to retain full activity, while others are exceptionally inert and stable. Many metals are attacked by the f., While some others form protective surface layers that prevent the progress of the attack to the underlying layers; so, as the lead reacts vigorously cold, aluminum, iron, chromium, nickel passivano for formation of stable protective veils cold; copper and gold are almost not at all attached.

The fluorination is the operation with which are introduced one or more atoms of f. in an organic compound. Several methods are: the most used consists in replacing the atoms of f. to atoms of other halogens already present in the molecule, and as agents for this operation using the tri- and antimony pentafluoride, hydrogen fluoride, fluoride, mercury or potassium. Other methods, of more limited application, are those of the electrolysis of a solution of hydrofluoric acid of the organic compound to be fluorinated and that of diazotization of an amine followed by decomposition of the diazonium salt to form the fluoride (method but of course only applies to aromatic compounds). Today the fluorination is widely used in the chemical industry, because the compounds that are obtained typically have exceptional properties of chemical and thermal stability.

The term fluorination is also used to indicate the coating of the outer surfaces of the lenses of optical instruments with an extremely thin layer of magnesium fluoride or cryolite, which allows to reduce 1-3% passive reflections, which amounted to about 4-7% of the transmitted light.