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amounts of the insoluble ruthenium trichloride were not successful. Platinum was successfully chlorinated and recovered in chlorinations under the conditions found optimum for ruthenium.

Moving plate studies showed that the available material which best matched the volatility behavior of boron in carbon and graphite in the direct current arc was finely powdered iridium. When the discharge was burned in a 76 to 24 (by volume) argon-oxygen mixture, the line pair B 2497/Ir 2543 gave intensity ratios having a relative standard deviation of 1.870 or less between 0.5 and 4 p.p.m. boron. By use of a powder spark method, the sensitivity was extended to 0.25 p.p.m. boron. In this technique, a "sifter" electrode (a porous cup electrode with a perforated floor) was filled with powdered sample and used as the upper electrode in a high voltage spark discharge. The opening at the top of the electrode was closed with a small cork. During the discharge, the sample material sifted into the discharge area and was excited. When this discharge was conducted in argon, the line pair B 2497ICu 2492 gave a relative standard deviation of 1.870 or less between 0.25 and 7 p.p.m. boron.

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