MnCl2 won't dissolve?

[tummo1997]

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.

[ChenBeier]

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.

[adamusa]

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.

[ChenBeier]

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

[pigkang]

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?

[ChenBeier]

Don't answer 2 Year old posts.