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learner1112
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[*] posted on 24-1-2015 at 22:53
mnso4 industrial route


i am trying to figure out an economical industrial route of processing mnso4 from natural ore. essentially mno2. the first process is to burn sulphur and inject the so2 formed into the crushed ore and water solution. the slurry thus obtained is kept at ph4-4.5 by adding lime. after the reaction the slurry is filtered and the liquid which is pink in colour is obtained. now the problem is how to seperate the mnso4 present in the solution. can anyone guide me, as when i try to heat the solution its ph goes down and it becomes acidic with evolution of so2 gas and probably the mnso4 is converted baqck to mno2.
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acetatecorp
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[*] posted on 21-4-2015 at 16:06
Manganese Carbonate


Thanks for the detailed procedure Peach, I followed your instructions and got the same fabulous result. Just one question about the Manganese carbonate:

It works great via the double displacement of the Manganese Sulphate and the Sodium Bicarbonate, but when done with Manganese Sulphate + Sodium Carbonate I get a fluffy brown precipitate that dries to a light brown powder with a carbonate feel. I've researched and looked up many photos of Manganese carbonate for sale and many of these are in fact brown. On other parts of the net the colour varies from white to light pink.

I've gone over the reaction equations also and I'm stumped as to why I get two very different results. Also, when making the acetate (II) from this brown powder & AA, the reaction does not work and produces a small amount of dark brown precipitate.
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acetatecorp
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[*] posted on 21-4-2015 at 16:10


Sorry, this is my first post on here and my question probably wasnt clear:

Does anyone know why there is such a huge discrepancy between trying to make the carbonate from Sodium Carboante VS. Sodium Bicarbonate?
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blogfast25
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[*] posted on 21-4-2015 at 16:54


Quote: Originally posted by acetatecorp  
Sorry, this is my first post on here and my question probably wasnt clear:

Does anyone know why there is such a huge discrepancy between trying to make the carbonate from Sodium Carboante VS. Sodium Bicarbonate?


There should be no discrepancy at all, assuming similar purities of the sodium carbonate and bicarbonate. Using carbonate will cause no CO<sub>2</sub> fizz, of course.

Technical grade MnCO<sub>3</sub> varies in colour from white with a pink tinge (very pure) to beige to beige/brown (quite impure). The contamination is almost always due to iron(III) oxide. Mn and Fe are often found together and are not so easy to separate. They will precipitate together using carbonate/bicarbonate, the iron as Fe(OH)<sub>3</sub>.

[Edited on 22-4-2015 by blogfast25]




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UC235
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[*] posted on 21-4-2015 at 17:29


On leaving some freshly prepared, moist manganese carbonate outside a few years ago it became a light brown from a pink-tinged white. I assumed that this was oxidation to MnO2, so the brown color of a commercial sample may not be entirely due to iron contamination.
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acetatecorp
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[*] posted on 21-4-2015 at 22:01


Thanks @blogfast25. I used cheap washing soda so probably very impure. I'll try getting AR grade sodium carbonate and test again or dehydrate some baking soda.
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blogfast25
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[*] posted on 22-4-2015 at 08:32


Quote: Originally posted by UC235  
On leaving some freshly prepared, moist manganese carbonate outside a few years ago it became a light brown from a pink-tinged white. I assumed that this was oxidation to MnO2, so the brown color of a commercial sample may not be entirely due to iron contamination.


The samples that weren't very white that I've analysed all tested positive for Fe(III).

Of course moisture is a vector for air oxygen, so some oxidation to MnO2 is a possibility. Mn(II) carbonate has a general 'reputation' for being stable though.

Quote: Originally posted by acetatecorp  
Thanks @blogfast25. I used cheap washing soda so probably very impure. I'll try getting AR grade sodium carbonate and test again or dehydrate some baking soda.


Or make a hot, saturated washing soda solution, hot filter carefully (sometimes it contains a bit of anti-caking MgO) and allow filtrate to cool and chill. Collect quite pure Na2CO3.10H2O. Repeat for super purity, if needed. The decahydrate isn't very stable though (loses water) and for stoichiometric work it's best dehydrated first.

Baking soda sometimes goes brown on heating because of rice powder as anti-caking agent. It's a test of purity: if it browns on heating it's not very pure.

[Edited on 22-4-2015 by blogfast25]




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