Needing more than a spark test?

I did a lot of work with manganese dioxide as an analytical chemist for a battery manufacturer. Manganese dioxide will work. The density will be less but that can be compensated for by a thicker layer. For the latter, I would mix with epoxy to make a paste and spread it on a backing film. The components in epoxy are basically carbon, nitrogen, oxygen, and hydrogen. The particular epoxy I used in another job was 7.90% H, 68.38% C, 2.98% N, and 20.57% O by weight. MnO2 is 63.19% Mn and 36.81% O.
I wouldn't consider potassium permanganate as it is reactive and contains a much lower % Mn. It's been a long time since I was a battery chemist but the black gunk in a battery is a mixture of MnO2 and C in the form of carbon black. Alkaline cells will have a KOH electrolyte and the mix should be washed thoroughly to remove it. Old fashioned zinc carbon cells used a zinc chloride electrolyte as I recall. Many of them had a small amount of HgCl2 as well.
 
Those high priced metals from Sigma Aldrich are so because of their purity.

When we used to do assays on manganese dioxide, we would digest the samples in concentrated HCl on a hot plate. This would make MnCl2 which is ware soluble. Start with the battery gunk and wash out any solubles. Then digest in HCl. Filter to remove the carbon. I havent tried it but you may be able to plate manganese from the solution. It may be possible to convert back to MnO2 by using NaOH. The MnO2 should precipitate out. Wash and filter to remove the NaCl byproduct as well as the residual NaOH.

edit: On further thought, the precipitate with NaOH would most likely be MnO. Also, the digestion process produces clorine as a byproduct so it should be carried out in a well ventilated area, preferably outdoors.
 
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One guy I read about plating Mn it showed up as a black precipitate loosely bound to the metal. That might just be poor technique though.
Robert
 
GrayTech said:
Why not just take it down to the scrapysrd and pay them a few bucks to XRF it for you.
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Hmm.. :)
1) I get an excuse to play in the shop with real RADIOACTIVE stuff in a darn good cause.
2) I get to do cool stuff with my grown-up chemistry set you would never find being marketed now.
3) We get to play with a kit that includes little computers doing cool stuff.
4) Discounting all the stuff we mangle on the way, if we end up with something that will effectively analyze the materials, costing maybe $200 to £300 in parts (mixed up currencies there!), instead of the $6K to $11K depending + some assembly and tryout adventures, I feel OK with that.
5) This is something I can see myself using way more often than I would want to trek to a XRF-equipped scrapyard for. I live rural. The stuff in the nearest place that might be called "scrapyard" is pretty agricultural.

Now that I have spent real money on a photo-multiplier tube (yet to arrive), suitable control tiny computer, radioactive mantles, various A/D electronics, and ex smoke detector innards Americium 241, the bill is mounting up. So far - about $75.
The only thing missing (so far) is the chance to make something explode!

Welcome to this (isolated) now not-so-little thread.
 
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GrayTech said:
Why not just take it down to the scrapysrd and pay them a few bucks to XRF it for you.
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Where's the fun in that :). And if you got something for free, you just made it cost something. This is about scrounging -- if we had all the money we wanted to we'd buy what we need and skip the analysis altogether. And if you're really concerned you can ask the supplier to include the material analysis (many include it anyway).
 
This all started because I have this pile of steel things, accurately machined, clearly something aircraft/military related, that will not rust, but are well magnetic. In making chips, it is rare that I go out and actually buy the steel. The back-plate for a previous lathe started out as a brake disc no longer OK to leave on a car .. and so on.

Yeah - I just realized I must sound like HM's biggest $$[ tightwad ] $$. :eek 2:
 
@homebrewed : If we are looking for purest elemental stuff, I have an plano-concave infra-red lens made of the purest germanium, about 25mm diameter. I am not sure it will provide a calibration line anywhere near where we are interested in, but if we need it, I can cut it up.
 
I did some calculations to see what would be needed in the way of a manganese energy filter, to separate the iron vs cobalt x-ray lines. It required interpolation on both sides of the absorption edge to get the attenuation factors for iron and cobalt. For iron, the mu/rho ratio came out to 62 cm^2/g and for cobalt it is 404.8 cm^2/g. If we assume the usual attenuation vs thickness equation is valid, I = I0*exp(-alpha*t), in this case "alpha" = mu/rho. Now if we are willing to accept a loss of 50% of the iron signal, what do we get for the cobalt line? I calculated that it would require a Mn filter that is .0112 cm thick to reduce the iron signal by a factor of 2. This would reduce the cobalt signal to .011 times its original intensity, so the ratio of iron/cobalt signals would be 45.6:1

Going with the idea of a metal powder in a polymer matrix, let's go a bit further. If we want to make a filter that is 2.5cm in diameter (about 1 inch), the total amount of Mn would weigh 254 milligrams. Not a huge amount, but I've got a small digital scale that goes down to 1mg. I'd mix up a lot more, cast and machine it down until I got the desired ratio between Fe and Co. The polymer blend filter could be much thicker than the bulk Mn filter, so the metal particle size wouldn't be so critical. The tricky part would be getting a uniform blend. It might be necessary to use some kind of "zero gravity" casting scheme, where the stuff is continually rotated so the effect of gravity is canceled out. Just riffing on the idea here, there probably are other approaches that would work.
 
graham-xrf said:
@homebrewed : If we are looking for purest elemental stuff, I have an plano-concave infra-red lens made of the purest germanium, about 25mm diameter. I am not sure it will provide a calibration line anywhere near where we are interested in, but if we need it, I can cut it up.
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Unfortunately, Ge's absorption line(s) aren't even close to what we'd need for any of the ferrous metals. They're all in the 1Kev range.
 
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