| Abstract: | Magnesium hydroxoaluminate hydrates were coprecipitated from different mixed metal cation solutions at Mg/Al2 ratios from 1 to 4 by ammonium hydroxide. The coprecipitations were monitored by potentiometric titration and the final precipitate compositions were examined by chemical analysis, X-ray diffraction, infra-red spectrophotometry and thermal analysis. The process of coprecipitation was similar to that for coprecipitation with sodium hydroxide but large excess of ammonium hydroxide was required for complete reaction at pHs from about 8 to 10. - At Mg/Al2 = 1, the main phase was probably Mg(H2O)h Al(OH)4]2;
- at Mg/Al2 = 2, the main phase was probably Mg2(H2O)h Al2(OH)10];
- at Mg/Al2 = 4, the main phase was probably (MgOH4) (H2O)h Al2(OH)10].
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