Alchemist
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Permanganate
Hello all,
Has anyone ever made or experimented in making Potassium Permangate"?
It is about impossibe to get in California! I have tried fusing Potassium
Hydroxide (from janitorial supplier)plus Manganese Dioxide (from pottery shop)
and some Potassium Chlorate (home made), but have NOT had any GOOD results.
Any help or comments would really be appreciated, or even better if someone
would also like to do some experimenting also. This is a compound that is REALLY
needed by many of us.
Thanks, the Alchemist!
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Polverone
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I have bought KMnO4 in the US from Sears; it was sold for regenerating certain iron-removing water filters. I think I paid $40 for 5 pounds. I've
heard of others finding it more cheaply than that at the fabled "hardware store." Then again, I've also bought toluene at hardware
stores in the US and I know it's not around in CA. Is it unusually regulated in California? Is simply ordering online an option, or driving to
Nevada or Oregon?
Did you you try acidifying the product of your fusion? I've made impure manganates by alkali + MnO2 but I have not tried to recover permanganates
from them.
The method given in Muspratt doesn't call for any acid, but it doesn't give suggested times for any of its operations either. It suggests
intimately mixing 4 parts finely-powdered MnO2 with 3.5 parts KClO3, and mixing this powder with 5 parts KOH dissolved in a minimal quantity of water.
The mixture is evaporated to (apparently) dryness, pulverized, then raised to a low red heat in a platinum (ha ha) crucible. The fused mass is again
powdered, then added to "a considerable quantity" of boiling water and allowed to settle. The clear liquid is decanted when all has settled.
If you want crystals, I assume you will have evaporate all the "considerable quantity" of water from this solution.
If I had a ball mill with hard milling media, that's how I would powder the KClO3 and MnO2 together. I have tried powdering ceramic-grade MnO2
with a coffee grinder and it does not work very well.
PGP Key and corresponding e-mail address
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S.C. Wack
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I used to make mine using air as the O source. The KOH that I was using at the time was in aq. solution - this was simply added to the MnO2, and
heated with stirring until solid. Then heated in a thin layer.
It seemed, with my pitiful heat source, that this was sensitive to temperature - there were green zones and black zones.
Water was added and the aq. manganate filtered through fiberglass. Though most books mention using Cl2, CO2 gas or dry ice to convert the manganate to
permanganate, simply boiling it and allowing to stand eventually got it purple. I'm guessing that the yield is worse with the way I used. Perhaps
it was absorbing CO2 from the atmosphere? The progress of this is easy to see, more and more MnO2 precipitates, and then the color changes.
So my guess as to your problems, assuming OK chems, would be degree of heating. For the chlorate, it shouldn't take long or extreme heat, if you
melt the KOH and stir in well the others. Don't give up on this one.
You might find it in CA in a rural area, as it seems to be sold for water treatment purposes, but only by certain chains. It isn't listed under
Proposition 65, surprising as just about everything is, as we excruciatingly creep towards Orwell. California faster than most everywhere. Toluene is
lately no longer sold in this state by the major chains either, but a jump over the river to the same chains and you find it. Don't count on
anything being available next week, month, or year.
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Theoretic
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You could try straight tossing thin MnO2 powder in molten KOH, then stir to make contact with atmospheric oxygen.
Edit: for faster disproportionation of the manganate solution, try blowing into the solution with a straw. 
[Edited on 20-10-2004 by Theoretic]
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Theoretic
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Oh, and a good oxidizing agent to make the manganate is NH4NO3. It leaves no nonvolatile residue, so doesn't swell the volume of the reaction
mixture unnecessarily. This works like so:
MnO2 + 2NaOH + NH4NO3 => Na2MnO4 + N2 + 3H2O
I said NaOH because it's easier to come by, a mole of NaMnO4 weighs less than a mole of KMnO4, less volume as well so when you use it for a
reaction your reactants take up less volume, and you can prepare NH4MnO4 more easily from it, since NaCl precipitates more easily than KCl (less
soluble) when you add NH4Cl. 
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hodges
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I've made it before using MnO2, NaOH, and KNO3. I heated these on low heat (using a candle to heat a test tube with a small amount of the
mixture in the bottom). I ended up with a hard black substance which a small amount of would turn water dark green. Upon adding ordinary HCl I got
the characteristic purple color. Don't know about purity or yield, but the solution definitely turned purple.
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Pyrovus
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I've managed to make permanganate from MnSO4 by oxidising in aqueous solution with Ca(OCl)2. The Mn++ was immediately oxidised to MnO2, but didn't seem to react
further. However, after leaving for a couple of days I noticed the solution had turned the characteristic purple of permanganate. I've made quite
a bit this way, although I haven't yet thought of a way to get rid of the chloride ions produced by the reaction of the hypochlorite (well, at
least one that doesn't involve precipitation as PbCl2 - I'm not too keen on lead compounds).
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neutrino
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Fractional crystilization should work. Boil your solution down and wait for crystals to appear. At this point, stop heating and insulate the solution.
If you're lucky, you should get one type of crystal come out.
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Alchemist
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Permanganate
Hello all,
Well I see some good stuff so far, lets keep it going till we can get a good usable crop and a good procedure. I am going to start experimenting
again myself.
Say Pyrovus, where did you get your MnSO4?
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tom haggen
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You can buy toluene by the gallon in Oregon, this is ture. But buying potassium permaganate? I've done a lot of shopping for odd ball chemicals
and this is one I've yet to run across. I've herd it can be obtained from foot powder? I checked out this resource to no avail.
alchemist
I know you can get MgSO4 as epson salt but I don't know where you can get manganese(II) sulfate?
[Edited on 21-10-2004 by tom haggen]
N/A
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Theoretic
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You can react MnO2 (relatively easy to come by) with H2SO4, any concentration. O2 will be evolved and MnSO4 will remain in solution.
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BromicAcid
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In my chemistry class today we did the determination of manganese in steel. Dissolved three .4000 g samples of commercial ground steel in 50 ml HNO3
(50%) and heated till dissolved. Added 1 g of ammonium peroxysulfate in each beaker and heated further. Obtained a clear solution. Added .5 g of
potassium periodate, it didn't really dissolve, just sat at the bottom. Heated, instantly the solution turned purple from permanganate, all
around the salt at the bottom at first but quickly spreading though the solution, taking the salt with it. Being that the class is quantitative
analysis this procedure is very close to 100% yield. Too bad no one has potassium periodate laying around. Other oxidizers may well work though.
As for using a molten salt method to obtain potassium or sodium permanganate, I've only heard it mentioned that it can be made this way,
I've never heard it can be made this way well. In my research spawned from the thread I made on NaOH as an oxidizing agent the best yields were
in the conversion to manganate, which can be acidified to yield the desired permanganate as mentioned upthread. However the environment you describe
could be used to make perferrates 
(Woah, my spell checker knew how to spell permanganate...)
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JohnWW
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The only problem with that colorimetric determination of Mn in manganese steel as permanganate(VII) by dissolution and oxidation with periodate(VII)
(which is not the preferred oxidant - plumbate(IV) or bismuthate(V) are better) is that ferrate(VI), the UV/visible absorbance spectrum of which
largely overlaps with it, and which is produced by the same oxidation, greatly interferes. An alternative "wet" method, not requiring
oxidation (but requiring acidification to prevent oxidation by air and subsequent hydrolysis) would be atomic absorption spectrometry, also enabling
analysis for other metals.
But both are much slower methods than the usual non-destructive method used in industry for performing large numbers of steel analyses for all metals
present, namely, arc emission spectroscopy. However, in the absence of pre-prepared standard ferrous alloys containing known amounts of other metals,
UV/visible or atomic absorption would be needed in order to calibrate an arc emission spectrometer.
BTW The empirical observation that Fe, unlike Mn, cannot be oxidized beyond the hexavalent state, appears to have been made 100 or so years ago, and
never properly re-examined since using the most modern preparative methods and techniques. I am fairly sure that at least perferrates(VII) and
possibly FeO4 could be made and stabilized under suitable conditions, e.g. by electrolysis at very low temperatures (in supercooled alkaline
solutions).
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BromicAcid
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The spectrophotometric analysis of permanganate concentration measuring the absorbance at 525 nm is highly accurate (for every .0002% off on the
manganese content we are we loose 1% off our grade, btw, I used the standard addition technique), I personally would not think it would be occluded by
ferrate to any mentionable percent, due to the acidic nature of the solution used, in my experience ferrate (VI) disappears very very quickly in
acidic solutions, solid ferrates actually dissolve with so much gas evolution that it looks like I'm dissolving bicarbonate on its reaction with
acid.
The complete treatise on inorganic chemistry gives some details on FeO2, which was the highest and most recently prepared iron oxide of the time.
High oxidation state iron chemistry has been much neglected in the last several decades to my knowledge. I wish I could find out more. The book also
has information on perferrates, or what could possibly be perferrates, and their preparation from fusion of iron compounds with chlorate and potassium
hydroxide.
As for my school's choice of oxidant, maybe they're just cheap, or maybe it was more expensive so they thought it would be better, or maybe
there were some toxicity concerns, or maybe, well, they are a huge corporation, logical reasoning is useless.
[Edited on 10/22/2004 by BromicAcid]
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Pyrovus
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I got my MnSO4 from a garden store - they sell it to correct manganese deficiency in the soil. It cost somewhere
around $7 Aus for 500g, if memory serves.
Never accept that which can be changed.
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frogfot
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Found out today that industrially they oxidise K2MnO4 to KMnO4 electrolytically.
Since we get lots of K2MnO4 from fusion of MnO2/KOH/KClO3, electrolysis would be a cheap alternative to CO2.
Oh, and I really like the idea with using KNO3 as oxidiser. Theoretically it should perform better than KClO3 simply because KNO3 is more thermally
stable toward decomposition, specially in an iron vessel.
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tom haggen
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I bought some KMnO4 from sears today. I went home and tried reacting the KMnO4 with glycerin and nothing happened? Is it a possibility that there is
some kind of stabilizing agent in the KMnO4? If that is the case, do you think It could be removed by filtering, and recrystallizing the KMnO4 in
water? I'm positive that my glycerin is 99%, I bought it in the pharmacy in the local grocery store. Any advice would be greatly appreciated.
N/A
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neutrino
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You might just have to use a bigger batch. In my experience, the mixture first has to heat up before it catches fire. How fast this happens depends on
the size of the permanganate crystals and insulation.
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BromicAcid
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A tiny bit of water actually helps the reaction between KMnO4 and Glycerin, if your reagents were too pure then there may be a problem there, in
addition what form was your KMnO4? Powder would be good but if it was prills there may be additional delay involved.
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tom haggen
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Powered the KMnO4, Problem solved.
N/A
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verode
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You can get MnO4- by
K2S2O8 +MnSO4+H2SO4 +Ag(catal. some)but also with
MnO2+KClO3+KOH=K2MnO4 very basic green You need KOH
Then add some water you get
MnO2(s) +MnO4- (aq)purple
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d010060002
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what is it under in sears? I looked on their website but couldn't find it
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entropy51
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I've bought it at Home Depot as
"Potassium Permanganate - Green Sand". It's hard to miss!
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blogfast25
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Sheesh, blindness is a serious affliction: permanganates are the topic of one of the longest threads on this forum: sticky thread in position
3 in this section. See here:
http://www.sciencemadness.org/talk/viewthread.php?tid=8480
Please let's not start all over again!
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