Blackwell Publishing Journal Backfiles 1879-2005
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Hydroxylamine hydrochloride (NH2OH-HCl) and hydrogen peroxide (H2O2) have been used in the past for selective dissolution of manganese oxide minerals. The methods reported, however, give poor recoveries. We tried to improve the methods in this respect. By stoichiometry, incomplete dissolution of Mn oxides is due to the lack of NH2OH-HCl added or to the lack of acid added in the case of H2O2 treatment. By increasing the amount of solution for a given amount of solid in the case of NH2OH-HCl and by increasing the acid concentration in the case of H2O2 treatment, we obtained rapid and complete dissolution of synthetic Mn oxides. The dissolution of natural samples, however, was slower than that of synthetic ones. Based on the results obtained, the improved methods are: (i) 0.1 m NH2OH-HCl, non-acidified, 2 hours' stirring, and 1 g solid in 2 litres solution; (ii) 30% H2O2 in 0.5 m nitric acid, 0.5 hours' stirring, and 1 g solid in 1 litre solution. The improved methods achieved almost complete release of manganese from samples without decreasing the selectivity of dissolution.
Type of Medium: