Chemistry Forum

Hi all,

I am trying to dissolve 2g of anhydrous MnCl₂ (pale pink powder/flakes) in 70ml demineralized water at room temperature with moderate manual stirring. Although solubility at RT is supposed to be high, I could not obtain the desired solution yet. All I am getting is a bright-brownish solution, from which, after resting for several hours, a very fine bright-brownish precipitate/fog settles. The remainder of the solution is visually clear and has a pH of roughly 6..7 according to an indicator paper strip.

I did some research on the WWW and all I came up with is that MnCl₂ solution should be pale pink, while the colour I am observing rather hints at MnO(OH) as a result of Mn₂+ oxidation.

Any ideas what the problem could be (aside from the one in front of the keyboard)?


Cheers,
T.

How is the demineralzed water made. Maybe organic from manufacturing inside. Use destilled water instead. Add 1 ml HCl to get pH of 5 to 6.
Or the crued product contain oxidiser substances.

The change in color of the light pink MnCl₂ solution to light brown and the appearance of a very fine light brown precipitate when left for several hours may suggest oxidation of Mn²⁺ to MnO(OH). This can occur in demineralized water environments, slope especially when air is present.

Thank you, but not answer 2 year old Thread please.

adamusa wrote: ↑Mon Oct 16, 2023 9:18 pm The change in color of the light pink MnCl₂ solution to light brown and the appearance of a very fine light brown precipitate when left for several hours may suggest oxidation of Mn²⁺ to MnO(OH). This can occur in demineralized water environments, geoguessr free especially when air is present.

According to my research, a proper MnCl₂ solution should appear pale pink. The brownish color and fine precipitate I’m seeing resemble characteristics of MnO(OH), which suggests possible oxidation of Mn²⁺ ions in the presence of dissolved oxygen.

Could it be that the Mn²⁺ is getting partially oxidized due to exposure to air during stirring? If so, would degassing the water or working under inert conditions help? Has anyone experienced similar behavior with MnCl₂ solutions or have insights on minimizing oxidation during preparation?

Don't answer 2 Year old posts.