The coprecipitation of Magnesium Nickel Oxalate Dihydrate Powders (solid solutions) from aqueous solution: Precipitate compositions and Cporecipitate Mechanisms

The coprecipitation of magnesium nickel oxalate dihydrates from mixed metal cation solutions was monitored by conductivity measurements. A series of coprecipitates was then prepared from 0.2 M solutions with Mg contents varying from 0.2 to 0.9 total metal cation and their compositions and structures studied by chemical analysis, infra‐red spectrophotometry, thermogravimetric analysis and detailed differential calorimetry. The coprecipitates with upto 20 percent Mg content were solid solutions with structures similar to nickel oxalate dihydrate, the coprecipitates with 20 to 80 percent Mg content were probably mixed solid solutions while the coprecipitates with over 80 percent Mg content were solid solutions with structures similar to magnesium oxalate dihydrate. The ionic equilibria in supersaturated magnesium nickel oxalate solutions were analysed and mechanisms are proposed for coprecipitations from solutions of different Mg/(Mg + Ni) ratios.