Reagents for scientific and research use, namely, for use as quantitative standards for assay of metal ions in aqueous solutions; Reagents for scientific and research use, namely, for use as quantitative standards for assay of metal ions in environmental samples; Chemical preparations for use in industry, namely, zinc ion solutions; Chemical preparations for use in industry, namely, zinc ion solutions containing known concentrations of zinc ion; Reagent kits comprising one or more metal ion s...