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A method has been developed for treating current-voltage curves obtained from steady-state measurements at the stream-Applications to experimental curves using thallium, cadmium and lead ions for reversible reduction Rate constants for the reduction of aqueous solutions of zinc ion in ing mercury electrode. and zinc ion for irreversible reduction are shown. several concentrations of potassium chloride are reported.

A convenient dual unitized apparatus is described for rapid electrolytic removal of heavy metals from solutions of reactive elements, such as alkali metals, alkaline earth metals, and aluminum, using a mercury ca thode of new design. The apparatus consists of a self-contained immersion electrode assembly coupled to a high-capacity Tungar rectifier and a suitable control panel. It allows convenient, efficient use.with high current densities, permits easy washing of the electrode assembly without re-solu-THE removal of interfering metals prior to the determination of other elements offers numerous difficulties. If precipitation of the undesirable elements is to be employed, it is necessary to anticipate occlusion and to choose a suitable method or reagent that will not introduce interfering elements. It is often difficult to obtain reagents sufficiently free from the element to be determined; sometimes, subsequent removal of excess reagent offers additional difficulties. By contrast, electrolysis with the mercury cathode ( 7) eliminates virtually all these problems when applicable. With suitable apparatus it is generally possible to perform the electrolysis in a fraction of the time required for most chemical separations, leaving a dilute acid solution almost completely free of metallic elements.According to Lundell and Hoffman (8), the metals which-are quantitatively deposited in the mercury cathode are: chromium, iron, cobalt, nickel, copper, zinc, gallium, germanium, molybdenum, rhodium, palladium, silver, cadmium, iridium, tin, rhenium, indium, platinum, gold, mercury, thallium, bismuth, and polonium. Other elements which are completely removed from solution but not quantitatively deposited in the mercury are osmium, which is partially volatilized as the tetroxide at the anode, selenium and tellurium, which are reduced to the elemental state but remain unamalgamated, load, which may be partially deposited on the anode, and arsenic,

The polarograph discussed is a convenient photoelectric recording instrument designed for use in precise, practical polarographic analysis. The polarograms are automatically traced on paper in plain sight of the operator. A unitized electrode and cell assembly, which operates at a constant temperature, is described. COMMERCIALLYavailable instruments for obtaining polarographie current-voltage curves can be divided into three classes: (1J manually operated indicating instruments which make use of either a lamp-and-sc&le galvanometer or a microammeter to indicate the current; (2) instruments which automatically obtain and photographically record current-voltage curves; and (3) the newest type which automatically traces an amplified current-voltage curve directly on paper by means of a recording pen. The last type of instrument has an important advantage in that a permanent visible record of the polarographic wave is traced while the voltage range is being covered, without recourse to photographic processes and without plotting points and drawing curves.The polarograph recorder described here is also constructed upon the direct pen-recording principle but differs from commercial instruments in that the pen closely follows a galvanometer light beam actuated by the original unamplified current and thus rapidly traces a highly accurate current-voltage curve.Because of this, and the instant visibility of the automatic, permanent record produced, this instrument is well adapted to both routine analysis and polarographic research.

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