A general improvement in recovery of silicon over that obtained using direct alkali fusion is noted in Table I. Improved retention of silicon from the cyclic polydimethylsiloxanes was particularly noteworthy. Because the major products from rearrangement of polydimethylsiloxanes are these cyclic species, it might be expected that results would markedly improve with all linear polymers. However, the silicon from linear polydimethylsiloxanes with molecular weights and boiling points below that of octamethylpentasiloxane (molecular weight 385, boiling point 230 °C) was not held sufficiently for quantitative use.Decomposition of phenyl-containing silicones generally gave recoveries of 90% or better with both the direct fusion and alcoholic alkali modified methods. Significant improvements were obtained with the latter method as shown in Table I.A variety of inorganic and organic samples were analyzed for silicon using these decomposition methods and spectrophotometric analysis. Typical applications were the analysis of silicon in silicon metal, cement, solid silicones, silicone emulsions, solvents, organic oils, silicone treatments (paper, fabric, leather), and biological samples (fluids, tissues).

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A small high-pressure ion-exchange system has been used together with liquid-liquid extraction to achieve decontamination sufficient to permit the determination by beta counting of Z49Bk isolated from highly radioactive solutions. A high-pressure pump forces solutions through a column of Dowex 50 resin (20to 40-tdiam particles) at pressures from 1800 to 2500 psi. The eluent is a dilute aqueous solution of a-hydroxyisobutyric acid of pH 4.2. The eluted 249Bk is purified by extraction into 2mthenoyltrifluoroacetone-xylene. I n this way the *49Bk is separated sharply from many elements including the actinides, fission products, and corrosion products. Separations can be effected at eluent flow rates as fast as 18 m l ern+ min-l, thereby minimizing loading time, elution time, and radiation damage to the resin. High-pressure operation makes possible the use of a long column (-2 ft) having a small free column volume (-1 ml).

No abstract

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