Computer Science
Scientific paper
Jun 1987
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1987gecoa..51.1539h&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 51, Issue 6, pp.1539-1547
Computer Science
Scientific paper
A precipitate of nearly pure hetaerolite, ZnMn 2 O 4 , a spinel-structured analog of hausmannite, Mn 3 O 4 , was prepared by an irreversible wprecipitation of zinc with manganese at 25°C. The synthesis technique entailed constant slow addition of a dilute solution of Mn 2+ and Zn 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 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 m in diameter. Zn 2+ ions are able to substitute extensively for Mn 2+ ions that occupy tetrahedral sites in the hausmannite structure. Hetaerolite appears to be more stable than hausmannite with respect to spontaneous conversion to 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.
Hem John D.
Lind Carol J.
Roberson Charles E.
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