Thermal decomposition of silicon tetraiodide was investigated in both standard iodide (de Boer) and intermittent flow systems for potential use as a method for preparing high purity silicon metal.Purity of metal obtained from operation of a standard iodide process cell appeared to be a function of impurities in crude silicon source material. Iodide metal having resistivities from 0.5-3 ohm cm in the single crystal form was produced from Electro-Metallurgical high purity silicon. When iodide metal was used as silicon source material, the resistivity of single erystMs of doubly refined metal w~ried from 3 8 ohm~em.Silicon of higher purity was obtained through thermal decomposition of fractionally distilled silicon tetraiodide in an intermittent flow system. After preparation of tetraiodide by reaction of resublimed iodine and Electro-Metallurgical high purity silicon, it was subjected to a 16 step distillation at 200 mm pressure in a packed quartz column. The modified iodide process silicon was pq, ypc, and tim resistivity varied in seven prepar,'~tions front 30 200 ohm-era

Hafnium was separated from zirconium by a fractional distillational procedure. The distillate false(3HfCl4.2POCl3false) was chemically treated to obtain HfO2 , which was chlorinated and subsequently reduced with magnesium to form hafnium sponge. Essentially pure metal was produced from the sponge by the thermal decomposition of hafnium tetraiodide. A résumé of the properties of iodide hafnium is reported.

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