Abstract: Tetraethoxysilane is purified by passing impure material through a gas chromatographic separating column at a temperature below the boiling point of the pure tetraethoxysilane. Separation of pure material from impurities occurs on the column, and the pure material is thereafter cooled and collected in a receiver. The purified tetraethoxysilane has 99.999999% purity based on metals content.

Abstract: A whole-body patient positioning and repositioning support for fixedly securing a patient in an original position during radiation treatment and for repositioning the patient to the same original position for subsequent radiation treatments. The support includes a foamed-in-place mold within a disposable plastic shell carrying a grid of radio-opaque members for generating a patient registration grid on X-rays for use in the evaluation and adjusting of the position of the patient to the original position using a sheet or straps between the patient and the mold.

Abstract: Thermally decomposable Group IIIa compounds are purified by conveying the relatively impure material through a prescrubber module, then heating the scrubbed Group IIIa compound and conveying same through a preconditioned gas chromatographic column packed with a porous polymeric material. After isolation, the purified material is cooled, demisted amd collected. Thermally decomposable Group Va compounds are purified by conveying the heated relatively impure material through a preconditioned gas chromatographic column packed with a porous polymeric material. After isolation, the purified material is cooled and collected.

Abstract: Elemental silicon is produced by a process and apparatus wherein relatively impure silane (SiH.sub.4) is purified in the gaseous state, while mixed with an inert carrier gas, to a content of electronically active impurities which is no higher than that of "electronic grade" silicon. The silane so purified is then thermally decomposed to form elemental silicon of electronic grade purity, without need for further purification of the elemental silicon itself. The silane purification is carried out by injecting the impure silane gas as a series of timed, spaced pulses into a carrier gas stream which transports the silane pulses to a gas chromatographic column, through which the pulses flow in sequence. The column has a porous polymer or a molecular sieve packing which is specially preconditioned to achieve high resolution separation of the components of the feed.