An improved process for producing high purity silicon results from the
reaction of sodium with pure silicon tetrafluoride gas, which produces
sodium fluoride as a by-product. The silicon tetrafluoride gas is formed
by decomposing sodium fluorosilicate. The sodium fluorosilicate is
produced by precipitation when fluorosilicic acid (FSA) is reacted with
the by-product sodium fluoride in closed loop process. Likewise, the
fluorosilicic acid is preferably formed at high purity using a source
material that consists essentially of silica by reacting the by-product
sodium fluoride with an acid to create reactive fluoride ions.