Catalytic microdetermination of mercury

An automatic spectrophotometric reaction-rate method is described for the microdetermination of mercury. The method is based on the catalytic effect of mercury on the reaction of ferrocyanide with nitrosobenzene. The time required for production of a small fixed amount of the violet product as given by a preselected change in the output voltage of a photoconductive circuit, is measured automatically and related directly to the mercury concentration. The possibility of masking interfering ions with EDTA was examined. Amounts of mercury in the range 0.25–2.5 /smg, were determined with relative errors of 1–2% in measurement times of only 15–120 sec. Results obtained with mercurial compounds, treated with bromine water, were within 1–2% of the theoretical values and results obtained with pharmaceutical preparations were within the range assigned to those preparations.