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Author: Subject: Manganese Chloride Crystals
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[*] posted on 6-1-2011 at 09:48


Quote: Originally posted by peach  
I know the manganese is there. It's a manganese chemistry and the solution is pink, and I've had pink solid back from it before. It's the purity issue.



Try washing your crystals with acetone. FeCl3 in small amounts is yellow. Worked wonders for my ZrOCl2.8H2O which went from light yellow to snow white...
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[*] posted on 6-1-2011 at 10:14


Indeed.

I will give the acetone a go at some point - the stuff is bubbling away right now with the hydroxides method, so I have to see how that goes (need to give it time).

The problem with the ferric chloride idea is that material came out of an alkaline battery, and was treated with sulphuric acid.

Iron sulphate is green.




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[*] posted on 6-1-2011 at 14:15


That separation of MnO2 and Fe(OH)3.nH2O using vinegar (or other weak acid solution) worked, you know...
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[*] posted on 8-1-2011 at 04:56


Keep your jars and containers appropriately rinsed and cover them (and the filters) whenever possible to keep the purity up.

Small amount of contaminated solution decanted and mixed with KOH to produce the insoluble hydroxides of the metals

Filtered through coffee filters and thoroughly washed to remove excess base and contaminating ions

Cake retained

Cake mush returned to the original contaminated mess and thoroughly stirred

Solution aerated for approximately 4 hours with a nebulizer (you can leave it standing for ages if you don't have a pump. Don't use a fridge pump for this - grease - needs to be an aquarium style one; diaphragm)

Filtered through yet more coffee papers

Ta-da... bubble gum pink

Filter the insoluble hydroxides. I'm using plastic funnels, coffee filters and Kilner jars to demonstrate it can be done without anything special - indeed, that being the reason for me choosing the hydroxide method, as it can also be kept reasonably pure and requires only some NaOH or KOH to repeat verbatim

The brown gunk is from treating some of the contaminated solution with base

Note the nomograph over the filter to keep things clean - everything has been thoroughly washed



There's the cake, the insoluble hydroxides. I'm filtering them away from the base solution. I have poured some extra water through and emptied the cake out to give it a swirl in some fresh water and to swap the paper. I used approximately 2-3l of water to rinse - ALWAYS RINSE BEFORE AND AFTER CONDITIONING FOR THE HIGHEST GLOSSINESS AND MOST LUXURIOUS HAIR IN TOWN.


Bubble boggling the solution - I have emptied the cake out into the remaining original solution (contaminated brown / yellow) and stuck a thistle funnel in there to blow air through, wrapping the top of the jar with cling film to keep dust, hair and everything else from getting in there

I'm using the funnel as it's clean and will keep the mess off the nebulizer

The Kilner jar I got at ASDA for £2, and it's absolutely great for this kind of work when you a.) don't have or b.) don't want to be bothered cleaning lab glass. The hinged top and rubber seal means you can easily cover the work if you want to stop for a while or go to bed, or leave it on the shelf for months :)

I bought this in the middle of doing the work when I ran out to get some more papers, thinking "ooooo.... that looks handy to prove the point"

The glass isn't suitable for extreme heating like borosillicate, but is close in terms of reactivity and the rubber the seal is made from is the same as the natural rubber used for Suba-seals (septum seals), stoppers and caps on Sure-seal bottles from sigma (it's all natural rubber).

Natural rubber WILL react with really reactive acids for example, but the art is in not storing your jars upside down :D

You could also up the seal rating by replacing it with a bead of silicone sealant - silicone is the classy version of Suba-seals normal natural rubber seals





Filter it again and the manganese salt (the chloride in this instance) should now have fallen away from the insoluble iron forms. The salt you're after will drip out, collect, look after, love and then set free


Or boil it down, your choice

Using the chlorides, or testing the end result with hydrochloric, may be good, as the iron chloride is extremely bright and has a high pigment value, meaning it'll show up well as you do this

This idea came from some inspiration on the part of Arthur, who mentioned dissolving battery casings in hydrochloric and not seeing any yellow - which is great! As I was concerned they may contain some iron. I'd used sulphuric for mine, but his mention of trying hydrochloric and not seeing anything has subconsciously inspired this idea of using the same reasoning with the manganese.

My zinc sulphate was also pristine white, and the sulphate of iron is green.

Those two things make me hopeful it's a source of decent purity zinc, which I will need for the bulk of the special paint.



What are you doing now!? I'll tell you what you're not doing.... opening my dinner!


YUM!

Really does look a lot like Bubbalicious bubble gum - second hand, but still good



Up-skirt cam


Carefully and gently drying the last of the excess moisture off before recrystalization - cam

Not bad at all considering the starting point and that all you'll really need are some papers and a bit of base - no fine pH control, no special gas handling equipment or practice and no contamination by the use of kitchen condiments



Thanks go to nurd rage for doing the original work.

[Edited on 8-1-2011 by peach]




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[*] posted on 8-1-2011 at 08:41


Splendid synthesis! Gives me some hope for my evil-looking tea-colored MnCl2/FeCl3 solution!

The results are indeed delicious-looking – like cotton candy – but I wouldn't eat a spoonful of that stuff! :o

I'll try to reproduce your excellent results soon, now if I can just find a place close by that has some KOH (sigh).

Robert




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[*] posted on 8-1-2011 at 11:20


Don't need KOH. :)

That's the beauty, I did this without using any of the special glass, equipment or chemicals.

NaOH will work - drain cleaner / lye / caustic soda

[Edited on 8-1-2011 by peach]




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[*] posted on 8-1-2011 at 11:30


All looks very interesting but thick as two short planks here doesn’t get it: you’re separating Fe(OH)3.nH2O from MnO2 by bubbling air through the slurry? MnO2 ends up as MnCl2? What reactions are involved?

It clearly works, so I’m interested…
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[*] posted on 8-1-2011 at 11:59


You've got most of it.

I'm starting with a big mess of the iron and manganese chlorides.

SOME of that gets split off and treated with base to produce the (insoluble) hydroxides of both - which are very well washed to remove the excess, soluble base.

The iron and manganese hydroxides go back into the original mess of iron and manganese chlorides, where they selectively convert the iron to the 3 hydroxide. The air is there to assist the production of the insoluble iron hydroxide.

For the sulphate, it looks like this

4Mn(OH)2 + 4FeSO4 + O2 + 2H2O -> 4MnSO4 + 4Fe(OH)3

The 4MnSO4 remains soluble, the Iron hydroxide goes insoluble, so filtering the result is all that's needed.

I doubt anyone is starting from something much worse than I did with this. Look back to the original photos, the stuff is on it's way to brown / black.

The thing I REALLY like about this is that it doesn't require pH control. I have a pH meter that will read to 0.001 (with a separate temperature input and a datalogger that I can make graphs with on the computer as it happens or store up hundreds of thousands of points for later), but very few others do. And I'm doing this to see if others can produce this special paint at home, so the method I use needs to be applicable to what others will have available and their level of ability - most of them are into electronics, not chemistry.

Have faith, you can yield the pink stuff from it - and it's not too difficult

[edit] I'd still be interested to know what that yellow was in the sulphuric treated beaker. Manganese sulphate... pink, iron sulphate, green..... yet yellow crystals. And no, it didn't go back to pink on re-hydrating it, but I bet the manganese is still in there.

[Edited on 8-1-2011 by peach]




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[*] posted on 8-1-2011 at 12:56


The bit I don’t get is why your in your mixed hydroxides (to be clear: Mn(OH)2 + Fe(OH)2/Fe(OH)2) Mn2+ doesn’t oxidise to MnO2:

Mn(OH)2 === > MnO2 + 2 H+ + 2 e-

Which definitely proceeds in alkaline/neutral conditions, as anyone who has ever precipitated an Mn2+ salt other than MnCO3 will testify to: the whitish Mn(OH)2 turns brown before your eyes, never mind blowing oxygen through it! Or even extensively washing it with water… I made some MnO once and the only way I know is precipitating as MnCO3, careful drying and ‘burn’ in inert atmosphere to MnO.

Of course you’ve got Mn2+ in the part you didn’t add base to. Now you mix it with well-washed Fe2+/Mn2+ hydroxides and start the blower. Now you selectively oxidise the Fe2+ to Fe(OH)3 while solubilising the Mn2+.

You must lose quite a bit of the Mn to MnO2, stuck in the Fe(OH)3.nH2O, right? Still, it’s quite a neat little trick…
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[*] posted on 8-1-2011 at 13:20


Well, if there's any acid left in the solution you add it to (a good possibility), the MnO2 is likely going back (partially) to the salt of that acid as it's re-added if it's formed in the cake. As will the iron, which means it should really be free of acid before re-adding the hydroxides.

I only used the supernatant from the battery extractions to produce the hydroxides, the bulk of the chlorides (the solid at the base of the jars) was left for treating with them.

This is likely a slightly lossy process. As is recrystalisation.

Quality is the issue here. It needs to be as pure as possible for someone who can't get anything more than papers and some general chemicals.

The manganese will be used as a dopant at below 1% to the bulk material, so a gram will produce over 100g of the finished paint.

The thinner the paint is applied, the better. Typical thickness are around a micron for commercial displays I think - not a lot at all.

I'm sure the materials could be made even purer, but if they don't work at this level, it's inaccessible to the people who want it. I am testing this accessibility.

I still have to find some easy, yet effective and pure method for reducing the sulphate for them. And then dope it, which means potentially a day or two of solid roasting the components to drive the manganese ions into the sulphide lattice.

Then spin coat it, and then test it.

The typical drive in temperature is around 600-900C, over the working temperature of borosillicate, so that needs sorting. And it's typically done under a reactive atmosphere using gases even I can't get, which also needs negotiating on their behalf.

LOTS to get on with! :D

[Edited on 8-1-2011 by peach]




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[*] posted on 8-1-2011 at 14:40


It probably works best if it's a real mix of Fe/Mn, not just 5 - 10 % Fe contamination. There, selective dissolution of the Fe(OH)3 (after complete oxydation of both to resp. III/IV) with weak sulphuric or acetic acid is simpler. The leachate will contain traces of Mn but the Mn part should be completely Fe free.
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[*] posted on 8-1-2011 at 19:41


I haven't read all of the thread so forgive me if this is a repeat- but-
Manganese sulfate, MnSO4 (AR grade), forms very beautiful large rose crystals. However, it seems to dissolve itself in its own crystal water when the temperatures are too high, and its tendency to form very highly saturated solutions cause it to crystallise rapidly (freezing the solution contained in a whole beaker) rather than forming a nice looking single crystal (i.e. hanging off a nylon thread).
Nonetheless, one of the prettiest of crystals I have seen!


[Edited on 9-1-2011 by chemoleo]




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[*] posted on 25-1-2011 at 19:56


Quote: Originally posted by chemoleo  
I haven't read all of the thread so forgive me if this is a repeat- but-
Manganese sulfate, MnSO4 (AR grade), forms very beautiful large rose crystals. However, it seems to dissolve itself in its own crystal water when the temperatures are too high, and its tendency to form very highly saturated solutions cause it to crystallise rapidly (freezing the solution contained in a whole beaker) rather than forming a nice looking single crystal (i.e. hanging off a nylon thread).
Nonetheless, one of the prettiest of crystals I have seen!


You're correct.

I've had a go at recrystallising some of the results from the manganese work and it's not a particularly fun activity.

You're dead on with the mention of them either being in solution or hanging onto their water of crystallisation.

In practical terms, for those wishing to have a go, that means your solution will gradually drop with evaporation then, once almost all of it is gone, the crystals appear and you don't really have a lot to pour off. And what you are pouring off likely has a lot of the salt still in it.

It also makes filtering small volumes difficult, if the solution is anywhere near saturation and cools during filtering. Even though hot recrystallisation doesn't work at all well, you can find solutions going 'slushy' and not draining through filters if they've been moved from somewhere warm to cool.

But anyway, it can be done with some care and if you can put up with losses. You can always use the still manganese rich waste as a lower grade material.

I dissolved the slop from the hydroxide precipitation clean up in the smallest possible volume of hot distilled water, then set it on the radiator (45C / 30-40% RH) with a filter paper over the top. The next day, enough of the water should be gone that the crystals have reappeared. The remaining water may prove tricky to pour off. In fact, I could turn the dish upside down and it wouldn't drain. I had to give it a gentle tap over about ten minutes to encourage it away.

I didn't empty it out into a filter paper because that would entail mushing the crystals back in with the water, somewhat defeating the point.


Done! And perfectly doable by you with a spoonful of caustic soda.


These may appear browner than they actually are, as the surfaces and floors of the rooms are all wood, so the light is always yellow heavy. Not to mention, I'm one of 'those people' who still use incandescent bulbs, since the dimmers don't understand the word efficiency. The salt is pink in person.


The crystals will take forever to dry out alone, so I'm putting them under vacuum before warming them up. The vacuum helps the water leave but, of equal importance is that, the manganese will go back to the oxide if it gets hot in the open atmosphere.


After an initial drying, they get crushed up and go back in


I started with 21g of damp, potentially mucky stuff


And now have around 6 of recrystallised, filtered, drier salt. Which should theoretically be cleaner but, lacking the plasma chromatograph I wanted to buy, I can't actually test that with any high degree of accuracy


What John is using his for

I'm using around 0.03 to 0.01g of the manganese salt as the dopant for a zinc sulphide based pigment - which glows when exposed to an electric field (like the displays in a Betamax).

0.026g of the salt is less than you'd pick up by pressing your finger tip into a pile of it.

Those fractions of a gram need very, very thoroughly mixing with the zinc sulphide. Preferably so every microscopic grain of the sulphide is in contact with the manganese.

Back on the ball mill... for another 24h...


The resulting slurry, the next day


Moisture is driven off under vacuum and a low heat, then it's put under a stream of argon. Argon is usually heavier than air, this cylinder however, is possessed by Regan and hovering, thusly.


The pigment is roasted at 450C...


for about...


a long time. This is typically done in quartz boats, in a tube furnace, and an atmosphere of carbon disulphide or something similar - wherein it takes about two hours. Using lower temperatures and an inert atmosphere will mean it takes longer for the manganese to migrate into the lattice of the zinc sulphide. It's a diffusion process. The heat causes the lattice to vibrate, allowing the manganese to wiggle into place. The hotter it is, the more wiggling going on, the faster it happens - ain't it always the way!


Looks like some oxygen was left in there. START AGAIN!

The pigment isn't displaying any electroluminescence at present. Likely because this batch has oxidised.

Another possible candidate is my less than ideal electrical test setup. I'm simply wiping some of the result over a capacitor I made by laminating pieces of kitchen foil, which then get connected to the mains - sans fuse. I'm looking for any faint signs of glow around the overlap between the foil.

I have also tried powering the foils up using a TENS unit, which allows me to switch from an AC to a DC signal, as well to vary the frequency up to 100Hz (should be fine) and the pulse width (but only to 250uS, which may not be so great).

I would expect to see some signs of life, even if the conditions aren't perfect, as the pigment will respond over quite a large range I'm lead to believe.

Commercial, EL pigment is silk screened at a few tens of microns in thickness. It is also more commonly sandwiched between two layers of glass, with one slide being sputtered with aluminium and the other being a transparent & conductive coating, placing the pigment directly in the field.

I have made this pigment before and it was a light sunset orangey / salmon pink colour after driving it in, perhaps due to me using slightly more of the dopant. I also purged that a lot more thoroughly.

Once I get a spare hose tail in the post and manage to find the needle valve, I'll have another go.

I may also dispatch by courier pigeon samples to those nerds better equipped with the power supplies, frequency generators and conductive slides to have a go with it


The plate capacitor he speaks of. I have also seen these phosphors being illuminated with twisted magnet wire, which may be a better idea, as it's likely the pigment will come into more intense spots of the field than it will around the periphery of these plates


[Edited on 26-1-2011 by peach]




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[*] posted on 26-1-2011 at 09:52


Oxygen must be the great killer here, at higher temps it will oxidise your MnCl2 in a jiffy. Hard to get rid of the last traces of O2, considering also just how little Mn2+ you’ve got in there. Ever considered using MnS (the only ‘flesh coloured’ sulphide, apparently…) instead of MnCl2? Or start from anhydrous MnCl2 and just dry ball mill that with the ZnS till kingdom come? Then calcine in anaerobic conditions?

All in all this strikes me as a Real Boffin Project requiring Real Boffin Toys…


[Edited on 26-1-2011 by blogfast25]
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[*] posted on 26-1-2011 at 10:51


Quote: Originally posted by peach  




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[*] posted on 27-1-2011 at 00:45


Finding information on how to do this is not particularly easy, as the majority of the people who are interested are making things that only really get sold to electronics companies, large amounts of it is in journal papers and they're far too expensive to be buying one by one. Also, the more recent the method is, the more likely it is to involve something too complex to do at home.

I was doing this after someone mentioned how it'd be good if electronics nerds could make it themselves, because then they could make all kinds of displays and visually exciting things. A lot of the phosphors require things you won't find at home. But zinc sulphide doped with manganese, both of those can be found in batteries, so it seemed like a possibility.

The first issue was obtaining both of those as simply and in the purest possible state using the most basic items and chemicals available. I've done that to the highest possible standard I think someone else with little or no chemistry knowledge could repeat.

But driving it in, as you point out, means that oxygen needs to go. Not only will oxidation ruin the manganese salt, it will start the zinc sulphide off going back to sulphate, which will then need washing out as well, as the sulphate isn't active. I haven't tried it with manganese sulphide, as all the information I originally found was related to use chlorides and sulphates, and getting those out of the battery paste wasn't difficult - particularly the sulphate since it doesn't involve the plumes of chlorine.

With those done, driving the manganese into the lattice is the only remaining problem. I am hoping, optimistically but it's better than being negative, that the diffusion rate will not be orders of magnitude lower at lower temperatures - meaning, doing it at 450C instead of 900C would mean it'd take days or weeks.

Obviously, borosillicate glass is not at all suitable for 900C work, and more so when it involves hours worth of exposure. And the average person wanting to make some of this pigment won't have quartz. I am also trying to avoid the use of special atmospheres beyond inert gas, as too many of them are extremely flammable or toxic.

Once I have the needle valve found, I will try again, but this time purging the sample much more thoroughly. Another problem with purging it is, there will likely be pockets of atmosphere distributed throughout the finely divided sample.

The sample is ball milled in a little methanol, which helps distribute the powders and encourages them to flow better. Otherwise, there's too high a chance you'll end up with the dopant staying in one place as it's milled. Removing the methanol is not tricky at all and other, easy, solvents can be used instead.

It may also be beneficial to remove the methanol once it's in the tube it'll be heated in, as the slurry will be much better packed once dry and less likely to be full of air pockets than a fluffed up and transferred sample. Another method to ensure it's well purged would be to suck the atmosphere out with a vacuum pump and then back flow the new atmosphere. Again, that's making it more complex for others.

If all that fails, I'd have to abandon wide spread repeatability and start with bits of quartz and hydrogen sulphide.

Finding useful things in failure, if my sample above has oxidised (which it likely has), it at least shows the manganese was well distributed, judging by the homogeneous colour tone.

[Edited on 27-1-2011 by peach]




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[*] posted on 27-1-2011 at 08:10


How about co-precipitating ZnS with MnS? To be honest, considering the ratio of Zn/Mn and the solubility constants of Mn(OH)2 (2 E-13) and MnS (3 E-11) I’m not even sure whether there is a pH range in which this is physically possible but that can be verified real easily. With such small quantities your Mn may truly be occluded into ZnS crystals, a finer dispersion you couldn’t dream of. Then carefully water wash, vacuum dry and the rest of it...

If you want to stick with MnCl2 then I think pulling high vacuum and backfilling with pure argon (perhaps even several times) is probably the only real possibility.

Something niggles at me that obtaining this electrical field sensitive material must be simpler than all this…


[Edited on 27-1-2011 by blogfast25]
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[*] posted on 27-1-2011 at 08:38


I doubt it.

The other materials used to do this include cadmium, blue diamond, indium phosphide, gallium arsenide & gallium phosphide. They're usually made on a nanoparticle scale using sol-gels, ultra high purity materials and by semiconductor companies with cylinders of ungodly toxic stuff. Quartz and tube furnaces are the basics for them.

I haven't seen a single reference to anyone doing it at home.

If anything, I'm trying to get away with using barely anything compared to how it's usually produced.

The precise mechanisms by which semiconductor fabrication functions are not often discussed in detail outside of journal entries. I've spent quite a lot of time wandering around university physics labs and studying it, so (outside of this forum) I'm interested in physics, electronics and machining as well. As an example, I consulted physicsforum.com (their version of SM) about bandgaps and doping and received a whopping one reply, from someone claiming to know it inside out, yet unable to explain what I was pointing out. Shuji Nakamura, who developed the blue LEDs, originally won $180 million from Nichia for the work - after he took them to court for giving him a $180 bonus for it. :o :D

[Edited on 27-1-2011 by peach]




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[*] posted on 27-1-2011 at 08:54


Well, in that case it sounds like you're trying to do the impossible. Good luck with that! ;)
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[*] posted on 27-1-2011 at 10:15


Quote:
The limits of the possible can only be defined by going beyond them into the impossible.

--Arthur C. Clarke




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[*] posted on 27-1-2011 at 12:36


'Impossible' was hardly le mot juste here: 'beyond your means' probably covers it...
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[*] posted on 27-1-2011 at 12:51


Beyond my audiences' means covers it better still, as I'm purposefully using the least toxic and most basic of things knowing they are more interested in the product than the chemistry - hence the Lego ball mill.

[Edited on 27-1-2011 by peach]




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[*] posted on 27-1-2011 at 14:13


You've kind of lost me there: your ball mill sure looks small but if it works, so what. Well, does it?
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[*] posted on 27-1-2011 at 15:14


It does.

I started trying to make this pigment not only for myself, but because other people are interested in being able to make it themselves (at home). These other people have spent most of their lives studying electronics and programming, so they are not at all well equipped in terms of chemistry - we're talking, they'll have to go out and buy test tubes, and they're going to have nothing in the way of chemicals.

Part of the goal was to see if I could make the pigment in a manner that they'd be able to repeat themselves. This is why I'm trying to use the absolute basics in terms of equipment, practical complexity and toxicity. The hydroxide precipitation method is an example of that, in that it is so simple compared to the others yet also functions so well.

I can't make the reagents much purer, given that this was supposed to start with a battery to make it accessible. That's done. I now need the driving in of the dopant to behave.

[Edited on 27-1-2011 by peach]




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[*] posted on 17-3-2011 at 11:23


Update on my synthesis of Manganese Chloride...

A while ago, I decided to use the hydroxide method to precipitate the iron impurities in my Manganese chloride solution I made out of battery crud and HCl, so I put aside 1/5 of the MnCl<sub>2</sub> solution and mixed it with NaOH.

I got a lovely chocolate milk-colored solution which rapidly deposited into a brown mush. Washed and filtered thoroughly and I dried the mush which gave me a few grams of very fine brownish powder.

Then the stuff got put away on the top shelf for a few months until now. So yesterday, I dropped the tea-colored Manganese chloride solution in a flask and with a small funnel, poured the hydroxide dust in the flask. Instant blackness!

The solution right now is pitch-black! I know I have to "aerate" the solution a bit for the reaction to take place, but I don't have an air pump for now. More to come during the weekend.

Robert




--- Art is making something out of nothing and selling it. - Frank Zappa ---
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