Time constraints on experimental studies of lead apatites

Authors

  • Justyna Topolska AGH University of Science and Technology, Al. Mickiewicza 30, 30-059, Cracow, Poland, Department of Mineralogy, Petrography and Geochemistry
  • Tomasz Bajda AGH University of Science and Technology, Al. Mickiewicza 30, 30-059, Cracow, Poland, Department of Mineralogy, Petrography and Geochemistry
  • Bartosz Puzio AGH University of Science and Technology, Al. Mickiewicza 30, 30-059, Cracow, Poland, Department of Mineralogy, Petrography and Geochemistry
  • Maciej Manecki AGH University of Science and Technology, Al. Mickiewicza 30, 30-059, Cracow, Poland, Department of Mineralogy, Petrography and Geochemistry
  • Gabriela Kozub-Budzyń AGH University of Science and Technology, Al. Mickiewicza 30, 30-059, Cracow, Poland, Department of Mineral Deposits and Mining Geology

Keywords:

Pyromorphite, Vanadinite, Experimental mineralogy, Dissolution, Synthesis

Abstract

The paper presents the results of experimental studies on the synthesis and thermodynamic stability of selected Pb-apatites in terms of criteria determining termination of the experiments. Based on the case study, we indicate difficulties in analysing the obtained experimental data. Time-resolved sampling of precipitate formed during a dropwise synthesis of pyromorphite was performed and the results were compared to the literature data. It has been concluded that the Ostwald ripening time for synthesized solids depends primarily on the chemical composition of the intended Pb-apatite phase. We presented that heterogeneity of precipitate affects its dissolution in terms of repeatability of the results and equilibrating time. A unique 9-year-long experiment on vanadinite stability at a pH range from 2.0–6.0 revealed that among all tested dissolution conditions only the reactions at the pH = 3.5 can perform as the basis for some thermodynamic calculations. It has been concluded that the rate of phase transitions in the Pb-apatites group can be misleading in terms of determining the equilibrium of the system, and the experimental setup designed particularly to provide reliable controls in this aspect should be involved. Means in this respect have been proposed.

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Published

2020-01-20

Issue

Vol. 63 No. 4 (2019)

Section

Articles

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