Determination of lead and bismuth in molybdenum trioxide briquette

Determination methods of small amounts of lead and bismuth, contained in molybdenum trioxide briquette which is charged into the steelmaking furnace as a substitute for the ferromolybdenum, have been studied. Crashed and powdered sample are dissolved in aqua regia and organic matters present are decomposed completely by the addition of perchloric acid. After being cooled, the molybdenum acid anhydride deposited is dissolved either with ammonia water in the presence of tartric acid or with sodium hydroxide. Lead is extracted with dithizone-tetrachloride solution in advance from the solution of pH 10, containing tartarate and cyanide, and then, separated from bismuth by shaking with 0.05 N nitric acid. Finally, lead is extracted and measured as dithizonate in dithizone-benzene solution. Bismuth is extracted and determined photometrically as diethyldithio carbamate in the carbon tetrachloride solution, after being separated and concentrated according to the ferric hydroxide coprecipitation procedure. In the use of the spectrographic detection, conbined with the dithizonate extraction, it is confirmed that the samples do not contain any amount of thallium, which is interfered with the determination of lead and bismuth. Analytical results some commercial briquettes and ferromolybdenums are shown in Tables I and II.