STUDIES ON AGING OF FRESH PRECIPITATES. XVIII: The Mixed-crystal Formation Between Barium Sulfate and Potassium Permanganate

Abstract

According to Grimm et al. (4,5,6,10,11) mixed-crystal formation between two chemical individuals may occur when the following conditions are satisfied: (1) the chemical building types of the two compounds must be the same; (2) the lattice types must be the same; (S) the lattice constants must be of the same order of magnitude. Similarity of chemical building types refers to pairs of compounds with the same number of cations and anions in which the corresponding ions are made up of the same number of atoms. The above conditions include not only the classical ones of mixed-crystal formation but also the formation of Grimm's "neuartige Mischkristalle." Examples of systems forming this new kind of mixed crystals are barium sulfate-potassium permanganate; barium sulfate-potassium fluoborate; calcium carbonate-sodium nitrate; lead sulfide-sodium bromide, etc. Grimm and his coworkers (4, 6) studied especially the new kind of mixed-crystal formation between barium sulfate and potassium permanganate. They coprecipitated potassium perman-SUMMARY 1. Upon shaking freshly precipitated barium sulfate with a potassium permanganate solution, distribution equilibrium is reached after fifteen