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woelen
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There is more to this than stoichiometry. Even if you add 10 times as much hydrochloric acid and you use pure MnO2, then the liquid still remains dark
green for a long time. This dark green stuff is a chloro complex of manganese in a higher than 2 oxidation state (+3, +4 or a mixed +3/+4 oxidation
state complex). Adding a few drops of H2O2, however, immediately destroys this complex and makes the solution colorless.
Mn(2+) ion is said to be pink, but even at high concentration it still looks colorless. The color of this ion is so weak that in practice I would call
it colorless.
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chemoleo
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Woelen, we had this conversation before....
MnCl2*x(H2O) is not practically colourless I'm afraid. My proof is analytical grade pink MnCl2 crystals... which dissolve in H2O at
supremely high concentrations, and of which remarkably beautiful pink crystals can be grown. I used MnCl2 * 11(IIRC) H2O for crystal trials, it works
nicely but needs crazy levels of saturation. The crystals are very beautiful, and melt easily. Sadly I redissolved the crystals to get better ones,
but currently I am not growing any because the ambient temp varies way too widely here atm to make decent crystals. Maybe in winter.
I need a dedicated temperature controlled room for these things!
Anyway.... MnCl2 is decidely pink, and not just at insane concentrations! If you really really don't believe me I'll upload a pic of my leftover
crystals... (to show I can back this up  )
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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12AX7
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I grew some crystals of MnSO4.H2O myself, they are slightly pink, very nice. Seems to be hexagonal. Hard, but cleaves easily, like FeSO4.7H2O
crystals do.
Unfortunately, in recrystallizing them, I dissolved them and the first crop removed was bluish. Now the solution is turning orange, and producing a
pale off-yellow scum in the bottom of the jar.
I ought to make MnCl2 some time, as well.
Tim
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chemoleo
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MnSO4 crystals suck, it doesn't really make nice crystals. Commerical MnSO4 is shipped as the monohydrate, and is totally a-crystalline (pink powder).
Not surprisingly, it dries on the heater as a powder.
The double MnSO4 salt of NH3 or K is ok, but altogether I wasn't impressed at all, compared to MnCl2, or the other transition metal (Ni, Fe, Cu) NH3/K
double salts. I'll post a thread on all these trials one day.
Anyway lets get this back to MnCO3.
[Edited on 16-7-2006 by chemoleo]
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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guy
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I used MnCl2 at my school once and it was really pink. This is because the chloride is part of the complex, Mn(H2O)4Cl2 unlike the sulfate salt.
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Rosco Bodine
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Eclectic has stated the easiest method in reacting a
hot solution of manganese sulfate from garden supply
with a hot solution of sodium bicarbonate or sodium carbonate to precipitate the manganese carbonate from
a supernatant solution of sodium sulfate .
If managnese chloride was desired , the manganese carbonate could be treated with HCl .
Alternately , hot manganese sulfate solution could be
treated with hot CaCl2 solution to precipitate CaSO4
from the supernatant manganese chloride solution which would form , the plaster filtered out and the residual solution evaporated to obtain the
manganese chloride ,
but this would not be as pure as the product from the carbonate intermediate .
Manganese could have usefulness in energetic compositions .
Filtered and rinsed manganese carbonate possibly could be boiled with ammonium nitrate solution until evolution of CO2 and ammonia ceased , and the
residual solution would be manganese nitrate , which could have usefulness as a metal ion detonation catalyst in ammonium nitrate compositions .
Strontium , Iron , chromium , and copper nitrates could also be useful , and lead nitrate has similar usefulness but these would likely require a
different method for synthesis .
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DeAdFX
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Manganese nitrate... In my high school chem storage I saw a solution of Mn(NO3)2 [If I remember the chemical formula correctly] which also
contained a small amount of nitric acid. Is the nitric acid used as a stabalizer to prevent hydrolysis?
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Rosco Bodine
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Generally those nitrates which are subject to hydrolysis to formation of basic nitrates are simply crystallized from
slightly acidic solutions and then kept dry . But a few drops of acid in the storage bottle can be used as an
added insurance against hydrolysis in long storage.
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woelen
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| Quote: | Originally posted by chemoleo
Woelen, we had this conversation before.... |
Yep, now you write this, I remember.
| Quote: | | [...] Anyway.... MnCl2 is decidely pink, and not just at insane concentrations! If you really really don't believe me I'll upload a pic of my
leftover crystals... (to show I can back this up ) |
I certainly believe you, so for that reason you do not need to provide pictures. Of course, pictures always are welcome for other reasons. They make
chemistry really alive!
I'll try to see that more intense color myself. I have the monohydrated MnSO4.H2O (I have a picture of that VERY light pink powder on my website).
I'll dissolve some of this in conc. HCl and see the more intense pink color of the chloro-complex. I'll make pictures of the solution and post them
here (also my website will be updated if I succeed in making this pink solution  ).
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woelen
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I did the experiment of dissolving some MnSO4.H2O in as little as possible reagent grade HCl (30%). The MsSO4.H2O also is a good grade chemical, and
not something from a pottery supplier.
The solution, however, does not show up as pink, it at first remains somewhat milky (the powder only dissolves slowly), but when all is dissolved, it
is only VERY pale pink, almost colorless, while the concentration is quite high.
Next, I decided to heat the liquid. Sometimes that aids in formation of complexes. When I do that, then I obtain fumes of HCl (driven out of the
liquid), and the liquid becomes pale yellow/brown/green. This can only be explained by assuming that a minor part has been oxidized by oxygen from the
air (or oxygen dissolved in the 30% HCl).
I added a pinch of Na2S2O8 to the liquid, and quickly the liquid turns dark green/brown, and some chlorine is formed. This shows that the manganese
(II) indeed is oxidized to a higher oxidation state.
So, from this I conclude that manganese (II) is VERY pale pink, almost colorless, at least under the conditions I had. Another interesting observation
is that the presence of a tiny amount of oxidizing species makes the liquid dark green/brown, exactly the same color, when MnO2 or KMnO4 is reduced by
hydrochloric acid. Apparently the reaction, which often is written as MnO2 + 4HCl --> Mn(2+) + 2Cl(-) + 2H2O + Cl2 is much more complex and in
reality there is an equilibrium, probably with some chloro-complex involved. For me it was very enlightening to see that the small amount of oxidizer
makes the liquid dark green/brown, even in this concentrated acid (hence large excess of HCl).
So, now I'm wondering how I could obtain that deeper pink color. Chemoleo, did you make that manganese chloride, or is it a commercial sample? Of
course, I still believe that you have such a deeper pink solution. I only wonder, what is the difference with my situation and why I don't get this
pink solution. This is a new chemical riddle, apparently there is more to say about this .
[Edited on 16-7-06 by woelen]
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Rosco Bodine
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Just thinking here further concerning the conversion of manganese carbonate to manganese nitrate , and wondering if this could have useful catalytic
effect in
lowering the decomposition temperature and accelerating the burn rate of other nitrate oxidizer
plus fuel compositions such as are used for rocket propellants . Ammonium nitrate has been experimented with as an oxidizer , but generally requires
something
really hot in the way of a fuel , like powdered magnesium
in order to get a decent burn rate .
What I am thinking is that * if * manganese nitrate
as part of the mixed nitrates was catalytic ...then
perhaps manganese nitrate could be added in small percentage to a tertiary eutectic nitrates mixture , like
the tertiary eutectic in Urbanski 3 , page 257 :
66.5% NH4NO3
21% NaNO3
12.5% KNO3 f.p. 118.5 C
and something like sorbitol could be used as a fuel ,
perhaps with some airfloat charcoal added to the melt
as a further combustion catalyst .
This would provide a very intimate mixture melt castable fuel , having a high percentage of ammonium nitrate
as the oxidizer . The combination of components
might just do the trick of getting the ammonium nitrate
to burn at a reasonably fast rate without the need for
magnesium . If it works , the fuel should have a lot more energy than the sorbitol / KNO3 mixture .
Potassium permanganate is another possible additive
but I think this one could be a dangerous addition in
a melt . Ammonium dichromate is another .
[Edited on 3-10-2006 by Rosco Bodine]
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sulfuric acid is the king
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Can it be produced by mixing aq sol of manganese chloride with sodium carbonate,or manganese sulfate with sodium carbonate?
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fusso
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Yes
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