THE THERMAL-DECOMPOSITION OF COPRECIPITATES AND PHYSICAL MIXTURES OF NICKEL-COBALT OXALATE DIHYDRATES

Physical mixtures and coprecipitated mixtures were made of nickel and cobalt oxalate dihydrates. These samples were studied by thermogravime try (TG) and thermomagnetometry (TM) in flowing oxygen or argon. The d ehydration indicated that the physically mixed samples behaved as sepa rate materials in two resolved steps while the coprecipitated material behaved as if it were a solid solution dehydrating in a single smooth step. The TM in argon revealed that the coprecipitates decomposed dir ectly to form a relatively homogeneous alloy. The physically mixed spe cimens on the other hand formed materials with very broad magnetic tra nsitions indicative of grossly inhomogeneous materials. These latter p roducts are probably the result of the formation of individual metals and their subsequent reaction within the time frame of the experiment. Reactions in oxygen formed mixed oxides in both instances.