Sciencemadness Discussion Board

Making manganese salts from manganese dioxide

Upsilon - 16-9-2015 at 17:27

What are some effective methods of making a water-soluble manganese salt from manganese dioxide? So far I have tried hydrochloric acid to make MnCl2, but I don't like doing it that way at all. I used just small amounts to test it; it kept going for hours, generating a billowing cloud of gagging chlorine gas (don't worry, I put it outside, far from anything).

I could go with other acids instead of hydrochloric, but these would take even longer (at least not generating a crapload of toxic gas in the process). I'm thinking sulfuric is the way to go, though this apparently requires heating. I've also looked into electrolysis processes that can reduce it to an Mn2+ salt but I can't seem to find a lot of information on how this works. Anyone have some advice?

DraconicAcid - 16-9-2015 at 17:46

You just have to add a reducing agent. Hydrogen peroxide works.

Oscilllator - 16-9-2015 at 17:57

Another thing that works (and is probably cheaper) is Oxalic acid. It also has the advantage of coming as solid crystals, so you don't have to work with dilute solutions.
There's a NurdRage video on this process somewhere, is you want more information.

Upsilon - 16-9-2015 at 18:24

Quote: Originally posted by Oscilllator  
Another thing that works (and is probably cheaper) is Oxalic acid. It also has the advantage of coming as solid crystals, so you don't have to work with dilute solutions.
There's a NurdRage video on this process somewhere, is you want more information.


I was considering this as well, but I feel like this would take a long time like the other reactions with acids. I'll try to find the video though.

[Edited on 17-9-2015 by Upsilon]

j_sum1 - 16-9-2015 at 19:17

Nurdrage has several great videos on this. The trick is to eliminate the Fe impurities that are nearly always present.
The method I like best is where he (cleverly) bubbles some SO2 through his solution. I will let you find it.

Upsilon - 16-9-2015 at 19:36

Quote: Originally posted by j_sum1  
Nurdrage has several great videos on this. The trick is to eliminate the Fe impurities that are nearly always present.
The method I like best is where he (cleverly) bubbles some SO2 through his solution. I will let you find it.


Yes, I've found the video. The manganese dioxide I have though is technical grade that I got online, so I don't think it would be nearly as contaminated as the stuff he got from the batteries.

Volanschemia - 16-9-2015 at 20:36

I may be wrong, but isn't Technical Grade < 90% purity?

DraconicAcid - 16-9-2015 at 21:12

I am not sure if I'm remembering correctly, or if I'm as drunk as aga, but I seem to recall once boiling MnO2 with alcohol and an acid to get the Mn(II) salt. Cheaper than oxalic acid, and then you don't have to worry about getting rid of the excess reducing agent.

Oscilllator - 16-9-2015 at 22:29

DraconicAcid's idea sounds great, but just FYI the reaction with oxalic acid is extremely vigorous. I remember I made the same assumption as you when I did this, so I added the MnO2 and oxalic acid together then added some water. The reaction started quickly and heated up enough to boil vigorously for a while so you won't have any troubles there. You may even wish to add the MnO2 to the oxalic acid solution slowly to avoid spattering.

Upsilon - 17-9-2015 at 06:07

Quote: Originally posted by Oscilllator  
DraconicAcid's idea sounds great, but just FYI the reaction with oxalic acid is extremely vigorous. I remember I made the same assumption as you when I did this, so I added the MnO2 and oxalic acid together then added some water. The reaction started quickly and heated up enough to boil vigorously for a while so you won't have any troubles there. You may even wish to add the MnO2 to the oxalic acid solution slowly to avoid spattering.


You're referring to the reaction in NurdRage's video that includes the sulfuric acid, right? Not just with MnO2 and the oxalic acid?