Abstract: A method and apparatus for determining electrochemically active components in a process stream. The method comprises the steps of providing a sample in which the components are contained, and depositing the components onto a working electrode, altering the environment of the working electrode so that it is immersed in a supporting electrolyte by effecting a matrix exchange and stripping the deposited electrochemically active components from the working electrode into the supporting electrolyte. The method and apparatus utilize a measurement cell which comprises a vessel (10) for containing the supporting electrolyte and a mercury drop electrode (150).

Abstract: A process for treatment of lead residues, without prior sintering, in which residues more than 70% of the lead is present as lead sulphates, comprising addition of the said residues, together with a reductant containing carbon and together with fluxes that will react to provide a slag containing FeO, CaO and SiO.sub.2, directly to an electric furnace operating at a temperature of 1000 to 1500.degree. C in the slag layer to produce in the furnace a lead bullion. The expression "lead sulphates" will be understood to include lead sulphate and other compounds containing lead and the sulphate ion, for example, the basic lead sulphates.