Manganese , solubility

Figure 7.4 Effect of pH cycling on the dissolution of manganese from crustal aerosols under conditions likely both in the atmosphere and on mixing into seawater (Spokes and Jickells, 1996). Manganese shows high solubility at a typical cloud water pH of 2. Solubility decreases slightly at rainwater pH of 5.5 and rapidly at pH 8. Extensive solution phase removal is not seen at pH 8 under conditions designed to mimic seawater, perhaps due to the formation of soluble MnCI+ and MnSOl-. Low pH cycling and inorganic complexation under seawater conditions increase manganese solubility six times over that seen at pH 8 alone.

Properties Soft, yellow, resinous, semitransparent. Mp approximately 0C. Gives deposits in highly acid oils but not when mixed with suitable quantities of cobalt or manganese soluble in alcohol. Combustible. 

Properties Hard, brown, resinous mass. It is a pale buff in color when precipitated in the cold, but darkens immediately in solution. Mp approximately 130-140C, commercial solution contains 6% manganese. Soluble in mineral spirits. Hardens on exposure to air. Combustible. 

Anaerobic organisms are able to use oxidized chemical species such as nitrate (NO ) as electron acceptors in place of molecular oxygen. Consequently, microbial reduction of nitrate to N2 (a process termed denitrification ) occurs in the early stages of soil reduction, as does Mn oxide reduction to Mn. Reduced species such as nitrite (NO ) and Mn then appear in solution. As more extreme reducing conditions develop, ammonium (NH ) accumulates from nitrogen reduction reactions, and iron solubility increases in the form of Fe. The elevated iron and manganese solubility is ultimately limited by precipitation of the rather insoluble carbonates of Fe (siderite) and Mn (rhodochrosite) if the soil pH is not too low ... 

Manganese solubility is controlled by the redox potential and pH of the soil. The Mn ion is a very soluble species in water, forming hydroxide and carbonate precipitates only at high pH (>7). However, as the pH is raised above 6 in soils. 

Reaction 3 represents a lower limiting value for manganese solubility. The commonly observed failure to reach this concentration in the initial precipitation in the laboratory is probably the result of more favorable kinetics for Process 1, in systems where Process 2 has not occurred to a significant extent. The release of Mn by Process 2 in natural open systems permits a local increase in dissolved activity near the oxide surfaces, and the surplus released by Process 3 can be absorbed by buflFer systems in the inflowing water. Thus the products of Reaction 2 become reactants in Reaction 3. 

What factors regulate iron and manganese solubility in wetland soils and sediment ... 

Figure 4-22. Iron-manganese solubility limits and the iron tolerance limit (Reichek et al., 1985) provides a guide to AZ91 corrosion performance. The numbers adjacent to the data points give the average salt spray corrosion rate (in mpy) of the die-cast samples.

In this reaction, manganese ions are oxidised and oxygen is involved as a reactant. For the A-site-deficient Lai, .Mn03, the manganese solubility in YSZ increases. However, the manganese dissolution does not change the conduction characteristics very much [47],... 

This reaction is also used on a large scale, to obtain iodine from seaweed. The ash from burnt seaweed ( kelp ) is extracted with water, concentrated, and the salts other than iodides (sulphates and chlorides) crystallise out. The more soluble iodides remain and the liquor is mixed with sulphuric acid and manganese dioxide added the evolved iodine distils off and is condensed. 

Divalent manganese compounds are stable in acidic solutions but are readily oxidized under alkaline conditions. Most soluble forms of manganese that occur in nature are of the divalent state. Manganese(Il) compounds are characteristically pink to colorless, with the exception of MnO and MnS which are green, and Mn(OH)2, which is white. The physical properties of selected manganese(Il) compounds are given in Table 6. 

Synthetic manganese carbonate is made from a water-soluble Mn (IT) salt, usually the sulfate, by precipitation with an alkafl or ammonium carbonate. The desired degree of product purity determines the quaUty of manganese sulfate and the form of carbonate to be used. For electronic-grade material, where the content of K O and Na20 cannot exceed 0.1% each, the MnSO is specially prepared from manganese metal, and ammonium bicarbonate is used (26) (see Electronic materials). After precipitation, the MnCO is filtered, washed free of excess carbonate, and then, to avoid undesirable oxidation by O2, dried carefljlly at a maximum temperature of 120°C. 

Iron and Manganese Removal. Soluble ferrous and manganous ions are oxidized by ozone (typicaUy 2.5 ppm) to less soluble higher... 

Metals. Transition-metal ions, such as iron, copper, manganese, and cobalt, when present even in small amounts, cataly2e mbber oxidative reactions by affecting the breakdown of peroxides in such a way as to accelerate further attack by oxygen (36). Natural mbber vulcani2ates are especially affected. Therefore, these metals and their salts, such as oleates and stearates, soluble in mbber should be avoided. 

Rubidium metal alloys with the other alkaU metals, the alkaline-earth metals, antimony, bismuth, gold, and mercury. Rubidium forms double haUde salts with antimony, bismuth, cadmium, cobalt, copper, iron, lead, manganese, mercury, nickel, thorium, and 2iac. These complexes are generally water iasoluble and not hygroscopic. The soluble mbidium compounds are acetate, bromide, carbonate, chloride, chromate, fluoride, formate, hydroxide, iodide. 

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