Synthesis and stability of hetaerolite, ZnMn/sub 2/O/sub 4/, at 25/sup 0/C

Journal Article · Mon Jun 01 00:00:00 EDT 1987 · Geochim. Cosmochim. Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(87)90335-8· OSTI ID:6938644

Hem, J D; Roberson, C E; Lind, C J

A precipitate of nearly pure hetaerolite, ZnMn/sub 2/O/sub 4/, a spinel-structured analog of hausmannite, Mn/sub 3/O/sub 4/, was prepared by an irreversible coprecipitation of zinc with manganese at 25/sup 0/C. The synthesis technique entailed constant slow addition of a dilute solution of Mn/sup 2 +/ and Zn/sup 2 +/ chlorides having a Mn/Zn ratio of 2:1 to a reaction vessel that initially contained distilled deionized water, maintained at a pH of 8.50 by addition of dilute NaOH by an automated pH stat, with continuous bubbling of CO/sub 2/-free air. The solid was identified by means of X-ray diffraction and transmission electron microscopy and consisted of bipyramidal crystals generally less than 0.10 ..mu..m in diameter. Zn/sup 2 +/ ions are able to substitute extensively for Mn/sup 2 +/ ions that occupy tetrahedral sites in the hausmannite structure. Hetaerolite appears to be more stable than hausmannite with respect to spontaneous conversion to ..gamma..MnOOH. The value of the standard free energy of formation of hetaerolite was estimated from the experimental data to be -289.4 +/- 0.8 kcal per mole. Solids intermediate in composition between hetaerolite and hausmannite can be prepared by altering the Mn/Zn ratio in the feed solution.

• Research Organization: Geological Survey, Menlo Park, CA (USA)
• OSTI ID: 6938644
• Journal Information: Geochim. Cosmochim. Acta; (United States), Vol. 51:6
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
SPINELS
GEOCHEMISTRY
REACTION KINETICS
STABILITY
SYNTHESIS
ACTIVATION ENERGY
CONCENTRATION RATIO
CRYSTAL STRUCTURE
MANGANESE COMPOUNDS
PRECIPITATION
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION
ZINC COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CHALCOGENIDES
CHEMISTRY
COHERENT SCATTERING
DIFFRACTION
ELECTRON MICROSCOPY
ENERGY
KINETICS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MICROSCOPY
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
SCATTERING
SEPARATION PROCESSES
TRANSITION ELEMENT COMPOUNDS
580400* - Geochemistry- (-1989)