axehandle
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H2SO4 by electrolysis of FeSO4
Sorry if this has been covered before, but
I happen to have 5kg of FeSO4 lying around in a bag. Would it be at all possible to use it to make dilute H2SO4 by electrolysis?
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axehandle
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And while on this topic, would lead be a suitable material for the anode or am I way off?
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chemoleo
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As far as I know, another old term for FeSO4-hydrate is iron vitriol - whereby vitriol is strong sulphuric acid.
If you heat up your FeSO4 to high temperatures (I dont think you'd need much more than 200 deg C), you should be able to distill off
SO3/H2O/H2SO4 vapours, which you could condense in a separate vessel. This is actually a nice experiment, always wanted to try this myself (even tho I
got plenty of H2SO4) 
On the note of electrolysis - I don't know if it is feasible. You need to find a way to prevent the iron from backreacting with the nascent
H2SO4.
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axehandle
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I already decided NOT to dry distill the FeSO4x7H2O (takes about 600C to decompose). Not fun, especially in a glass vessel. I would have to use my
propane
melting furnace, with a steel container with
the FeSO4.
What about using an iron cathode? The freed
Fe2+ (or is it Fe3+) would then simply integrate with the cathode.
I read in another thread that someone had
successfully used the method using cupric sulfate (with a copper cathode, offcourse).
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chemoleo
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Ok, sorry, I didnt realise you were aware of the thermolysis method.
I am not sure, again, whether it would work to plate out the iron as you would with the copper.
It's simply because iron is more reactive, and I imagine you would create iron hydroxide or something at the cathode (which would then backreact
with free H2SO4). Even if you did manage to plate the iron, then you'd have trouble to keep it from dissolving with free h2SO4.
Anyway, just try it and see whether you get plating!
PS I am surprised it takes such a high temp to decompose it! You are right, this is way too high to do it yourself easily
[Edited on 21-1-2004 by chemoleo]
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axehandle
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No need to apologize... =) I actually stumbled across the method as the alchemist way of
making sulfuric, but gave up after testing it. The borosilicate glass vessel I used when heating the (dehydrated) FeSO4 actually melted without any
sign of FeSO4 decomposition.
Ah well, if it were this simple, someone has already done it but I'll give it a go anyway.
I'm going to use a steel cathode, a carbon anode and an ATX power supply that's good
for 9A at 12V.
I'll get back to you all on whether I had any success or not (my guess is not, but hey, it's worth a try).
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axehandle
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The cells's been running for 15 mins, bubbles are forming on the aniode side (SO3?), the steel cathode gets plated with a black powder which I
strongly suspects is FeO.
Which would indicate that the method works.
But we'll see, I'll leave it running for some hours.
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guaguanco
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| Quote: | Originally posted by axehandle
The cells's been running for 15 mins, bubbles are forming on the aniode side (SO3?),
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The bubbles are more likely to be O2 (if I have my anodes and cathodes sorted out correctly).
SO3 is not particularly gaseous, and you'd know it if you had SO3 vapor floating around!
At the cathode, you're probably producing Ferrous ions and Fe(OH)2 (or some such).
How pure is this FeSO4 you are using?
(Note: I'm at work and not thinking too hard about this...)
[Edited on 21-1-2004 by guaguanco]
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kryss
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You'll get an equilibrium setup between iron deposition at the cathode, and deposited iron dissolving in the H2SO4 your forming.
What you need to do is to use a saltbridge the way you do when you make caustic from NaCl, and not allow products at the anode and cathode to mix.
Realistically the easiest way is destructive distillation - just dont let the gases escape, you'll need to sort out a cooling mechanism and
prevent suck back.
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axehandle
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That's what I've figured. Sigh. There's iron deposit on the cathode now, but it seems to stay constant.
A bad day for science, this. I'll have to go with my melting furnace method (shudder).
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axehandle
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I think I'll contruct a saltbridge from a bent
glass pipe, saturated KNO3 solution and
some wallpaper glue --- how hard could it be?
To guaguanco: The FeSO4 is extremely pure,
got it from my pottery supplier at an exhorbitant price.
Gagh! JUst woke up at 6am after a dream about salt bridges.... this is beginning to look
like obsession..... =)
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axehandle
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rethought
Or, now that I'm fully awake, I'll just go with
finishing my high voltage HNO3 generator,
make some catalyst out of aqua regia, platinum, ammonia and diatomaceous earth, and simply use the contact method.
It's probably less messy than this disgusting green stuff everywhere.
Edit: I'm going to use the bell jar method. Only difference between the lead chamber process if that I intend to ball mill stochiometric amounts
of sulfur and potassium nitrate and press it into fuel sticks using my hydraulic press --- that should give a slow, consistent burn.
[Edited on 2004-2-12 by axehandle]
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