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Manganese(II) chloride
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1. $H_2S$ |
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No pr. in acid medium! |
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2. $(NH_4)_2S$ |
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$Mn^{2+}$ $+$ $S^{2-}$ $\longrightarrow$ $MnS$ - Light pink precipitate - Soluble in dilute mineral acids - Soluble in acetic acid - Darkens slowly in air! |
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3. $KOH$ |
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$Mn^{2+}$ $+$ $2OH^-$ $\longrightarrow$ $Mn(OH)_2$ - White precipitate - Darkens slowly in air! - Browns quickly with $H_2O_2$, $Na_2O_2 $ or $ Br_2 $ by successive oxidations: $Mn(OH)_2$(white)$\longrightarrow$ $Mn_2O_3$(brown)$\longrightarrow$ $MnO_2$(brown) |
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4. $NH_3$ |
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Ammonia gives a sequence of events similar to those reported sub 3) The mixture $NH_3-NH_4Cl $ produces a temporary complexing followed by slow and uncertain decomplexing! $ 2 Mn^{+} $ $ \longrightarrow $ $ Mn(NH_3)_6^{2+} $ (hexammine cation, soluble, colorless) $\longrightarrow$ $Mn^{III}$ et $Mn^{IV}$ (brown-black) |
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5. $PbO_2/HNO_3$ |
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By the simultaneous action of both substances, the manganese is transformed to e.o. VII: Add to the solution for analysis a pinch of solid $PbO_2$ and some mL $HNO_3 $ ; bring to the boil for about 3 minutes! Wait for suspensions to settle. - The presence of $ Mn $ is revealed by a violet color! - The reaction is inhibited by an appreciable amount of $Cl^- $ - $ PbO_2$ used must be strictly free of $ Mn $! |