Abstract: A device for providing a signal emulating the wetness of plant leaves, includes a first generally horizontal surface; a second, generally upwardly facing sloped surface having an edge spaced above the first surface by a gap, so that drops of moisture can accumulate on the second surface, and run off the edge, bridging the gap, and first and second leads extending from the first and second surfaces, respectively, to measure the conductivity/resistivity across the gap. Also disclosed is a method of providing a signal emulating the wetness of plant leaves including the steps of: providing a first generally horizontal surface; providing a second, generally upwardly facing sloped surface having an edge spaced above the first surface by a gap, so that drops of moisture can accumulate on the second surface, and run off the edge, bridging the gap between the first and second surfaces; and measuring the conductivity/resistivity across the gap between the first and second surfaces.

Abstract: Aqueous solutions containing metal cations, that may include cations of both desired metal and impurity or secondary metal, are treated with an organic liquid extractant suitable for the extraction of cations of the desired metal, cations of at least one secondary metal being co-extracted. After phase disengagement, the loaded organic phase containing cations of either a desired metal or desired metal together with at least one secondary metal is contacted with a solid metal or solid metal alloy capable of reducing in the organic phase cations of either a desired metal or a secondary metal from a higher to a lower state of oxidation. Depending on the extracted metal(s) and the added solid metal or alloy, cations of the at least one extracted metal are reduced to the lower state of oxidation and either are deposited (cemented) in the metallic state onto the solid metal or alloy, or are partially reduced in the organic phase to a lower oxidation state with the solid metal or alloy being oxidized in part.