THE method described'the substance is decomposed by action of sulfuric and nitric acids, and the arsenic is precipitated by hypophosphorous acid. The arsenic is collected on a filter and is then dissolved by action of excess bromine (from Koppeschaar's bromate-bromide solution) in measured amount. The excess bromine is determined iodometrically. This procedure is well suited to the analysis of relatively small (semimicro) samples, for the reason that in the oxidation in-