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The Solubility of Mixed Magnesium‐Aluminum Hydroxide in Various Aqueous Solutions
Author(s) -
Hunsaker V. E.,
Pratt P. F.
Publication year - 1970
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1970.03615995003400050041x
Subject(s) - chemistry , hydroxide , aqueous solution , magnesium , solubility , inorganic chemistry , leaching (pedology) , montmorillonite , nuclear chemistry , aluminium hydroxide , aluminium , organic chemistry , geology , soil science , soil water
The object of this study was to investigate the release of Mg to water and various aqueous solutions by synthetic crystalline Mg‐Al hydroxide and the same material freshly precipitated on hydroxy Al‐montmorillonite. Washing in centrifuge tubes and leaching columns was used to determine the amount of Mg released by 50‐mg samples of the synthetic mineral in water, in solutions of NaCl, and in solutions of NH 4 NO 3 and NH 4 OAc at pH 6.0 and 9.0. Mixed Mg‐Al hydroxide, precipitated on hydroxy Al‐coated montmorillonite, was also leached with similar solutions. NH 4 OAc buffered at pH 6.0 released nearly 25% of the Mg present in crystalline mixed hydroxide, while NH 4 NO 3 at pH 5.7 and NaCl at pH 6.3 released 11.5% and 4.2$, respectively. The dissociation of the mixed Mg‐Al hydroxide, either well crystallized or freshly precipitated, is strongly dependent on the pH of the solution and, therefore, the weakly acidic NH 4 solutions were very effective in releasing Mg. The mineral is partially soluble in water and only slightly more soluble in NaCl.