Manganate salts

There are two manganese(II) sulfides, MnS and MnS2. Manganese(II) disulfide contains a S—S bond and has a pyrite stmcture. When a solution of a manganous salt is treated with ammonium sulfide, a flesh-colored hydrated precipitate is formed which is comprised of MnS and Mn(II)S2. This mixture very slowly changes to the mote stable green-black MnS. 

Fia. 2. Type I spectra of crystalline hydrated manganous salts. 

The spectra of ordinary hydrated salts of divalent manganese are of type I, and are essentially indistinguishable. In general, these salts contain the Mn++ ion octahedrally coordinated with oxygen. Figure 2 presents spectra of the crystalline manganous salts Fig. 3, the noncrystalline. Spectra of manganous salts show maxima at 16 and 60 ev. and a minimum... 

Fia. 4. Spectra of two manganous and the corresponding manganic salts locations and widths of peaks change with valence, but spectra remain of type 1. 

Manganese(II,III) oxide reacts with dilute acids forming the corresponding manganous salt and manganese(lV) oxide, Mn02 ... 

Pure manganese(IV) oxide (precipitate form) may be prepared by reducing permanganate ion with a manganous salt ... 

To synthesize Pa-233, thorium nitrate is irradiated with neutron. Pa-233 formed, as shown above, is dissolved in 3M nitric acid. The solution is heated. A manganous salt and permanganate are added to this solution. Manganese dioxide, Mn02, is precipitated. Pa-233 co-deposits onto this precipitate. The precipitate is washed with water. It is then dissolved in 6M hydrochloric acid. 

Alkyl hydroperoxides are known to be oxidized to alkylperoxy radicals by cupric, cobaltic, and manganic salts. Although CeIV has not yet been reported to oxidize hydroperoxides and although mechanisms for ionic oxidation of alkoxy derivatives have not been put forward, Reaction 1 is a possible first step. 

The even series of Group VII. contains one element, manganese, the only metallic element of the grotip. It resembles chromium in some respects, and also iron, although the manganous salts are stable and the manganic salts unstable. 

Manganous salts form addition compounds with bases such as pyridine, quinoline, hydroxylamine. These are generally more stable than the true ammines. 

Manganous salts unite with organic bases, generally with formation of di-derivatives. 

In aqueous solution, manganous salts are oxidised to manganese dioxide,6 and if silver nitrate is present as catalyst, to permanganate 0 the latter change constitutes Marshall s reaction. Chromium solutions in a similar manner give rise to chromate,7 even without a catalyst. Ferrous and cerous salts are converted into ferric and ceric salts, respectively, and phosphites are oxidised to phosphates. 

Another interesting example of induced oxidation is the reaction between chromic acid and a manganous salt in the presence of arsenious acid.12 The chromic acid is reduced to a chromic salt, while the manganous salt is oxidised to the manganic state and the arsenious acid to... 

The relation of Mnn oxidised to Asm oxidised is known as the induction factor, and is found to be about 0-5 at the beginning of the reaction, whatever amount of manganous salt may be present but the value diminishes as the action proceeds, for as the chromate concentration falls, the tervalent manganese is reduced by the tervalent arsenic to an increasing extent. The presence of a trace of potassium iodate produces great irregularity in the induction factor and lowers its initial value to about 0-25. 

Formic acid solution reacts as follows 11) with hydroxides, oxides, carbonates, to form formates, e g., sodium formate, calcium formate, and with alcohols to form eslers (2) with silver of ammonio-silver nitrate to form metallic silver (3) with ferric formate solution, upon heating, to form red precipitalc of basic ferric formate (4) with mercuric chloride solution to form mercurous chloride, white precipitate and (SI with permanganate lin the presence of dilute H-SOj) to form CO and manganous salt solution. Formic acid causes painful wounds when it ennies in contact with the skin. At IhO C. formic acid yields CO plus H . When sodium formate is heated in vacuum at 300°C. H- and sodium oxalate are formed. With concentrated ll.SOj heated, sodium formate, or other formate, or formic aeid. yields carbon monoxide gas plus water. Sodium formate is made by healing NaOH and carbon monoxide under pressure at 2I0 C. 

H. Braconnot showed that an alcoholic soln. of nitric acid is often less active than the aq. soln. He said that the alcoholic soln. acts feebly on bismuth, zinc, and copper because of the low solubility of the nitrates of these metals in alcohol and that it does not attack mercury because of the insolubility of the nitrate in alcohol. P. Pascal discussed the action of mixtures of sulphuric and nitric acids on aluminium, steel, and lead. The addition of sulphuric or nitric acid to a manganic salt or manganese dioxide, in the presence of hydrofluoric, phosphoric, or arsenic acid, may convert the whole of the manganese into the corresponding manganic salt. J. Jannek and J. Meyer found that cone, nitric acid distilled with platinum apparatus contains impurities not found when vessels of fused-quartz are employed. G. P. Baxter and F. L. Grover said that if clean, well-seasoned platinum is used, the results are as good as with quartz provided the acid is free from traces of hydrochloric acid. 

We have looked only at acid solutions since relatively few simple cations M +(aq) can exist in appreciable concentrations at alkaline or even neutral pH values. Note that in Fig. 5.4, Mn(IV) is represented by Mn02(s) and not by Mn4+(aq), while the higher oxidation states are represented by anionic species. The relative stabilities of the oxidation states are strongly pH-dependent. Thus Mn2+(aq) is quite difficult to oxidise to Mn3+(aq) in acid solution. When a manganous salt is dissolved in water and the pH adjusted to about 10, Mn(OH)2 is precipitated. If allowed to stand in contact with air, this undergoes oxidation to an Mn(III) hydrated oxide usually (but erroneously) formulated as Mn(OH)3 ... 

When a caustic alkali is added to a solution of a ferrous salt, white ferrous hydroxide is precipitated. This readily oxidises in air, yielding brown, ferric hydroxide. A manganous salt behaves in a precisely similar manner. It is instructive to note, however, that when ammonium hydroxide solution is added to one of a manganous salt in the presence of ammonium chloride, the hydroxide is not precipitated, and under similar conditions ferrous hydroxide is only partially thrown out from a solution of a ferrous salt. 

Reactions and Detection.—Permonophosphorie acid is a strong oxidising agent. It liberates iodine at once from acidified potassium iodide (cf. Caro s acid) and oxidises manganous salts in the cold to permanganates. Hydrolysis in dilute solutions is represented by the equation... 

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