Low-temperature nucleation of magnesite and dolomite

By way of duplicating an experiment described by LIEBERMANN (1967), nucleation of magnesite, huntite and/or dolomite has been attained at temperatures between 313 K and 333 K and under atmospheric pressure. Essential to these experiments are fluctuations in pH value. After interrupting an experiment after 1, 3, 5, or 8 of such fluctuations, the change from one or more metastable phases into the stable phase (magnesite or dolomite) could be followed. A theoretical explanation for these low-temperature syntheses can be found in stability relations. OSTWALD'S Rule stipulates the nucleation of a metastable phase before that of the stable phase. However, fluctuations of sufficient amplitude and duration are capable of crossing the border between the metastable and the stable fields. As a result, the stable phase will nucleate together with the metastable phase. Conditions opposing the subsequent growth of the metastable phase (such as the slightly acidic conditions resulting from periodically introducing CO2 into the solution) will favour the continued growth of the stable phase.