bbartlog
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Electrolysis of Salt
| Quote: | | the process can be done in a glass container with aluminum foil electrodes |
What process? Do some reading... aluminum isn't a suitable anode for, well, anything. Maybe it finds use as a cathode somewhere but I kind of doubt
that too. Anyway there are already massive threads in this forum devoted to the topic of producing almost any one of the chemicals on your list via
electrolysis.
The less you bet, the more you lose when you win.
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AndersHoveland
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This thread should be moved to 'beginnings'
Usually the electrolysis of salt water just gives off chlorine bubbles at the anode, and hydrogen gas at the cathode. The electrolysis of salt water
is now the main industrial process for making sodium hydroxide.
If the salt water is kept warm (or hot), sodium chlorate can be made.
If high currents are used, it is possible to make sodium perchlorate. Presumably the hydroxyl radicals that form oxidize the chlorate to perchlorate.
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hissingnoise
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| Quote: | | If high currents are used, it is possible to make sodium perchlorate. |
Perchlorate synthesis doesn't require higher currents than chlorate synthesis does; it requires a somewhat higher voltage, though!
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elementcollector1
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I heard you can use jello as an ionic membrane for pure NaOH / HCl + HOCl. Is this true?
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Pyridinium
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I have done some experimentation with animal gelatin as an electrolysis membrane (not with salt though) and have gotten an interesting result. One of
these days I have some pictures to post. Definitely some side-chain happenings there.
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elementcollector1
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Can this still make pure sodium hydroxide?
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hissingnoise
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Is NaOH not easily available everywhere?
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elementcollector1
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It's expensive. Electricity, Jello and sodium chloride are not.
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Zan Divine
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I can buy a pound of Red Devil lye for about $4. I wouldn't consider the electrolysis cheaper unless you place no value at all on your time. Wouldn't
you rather get on with whatever you wanted the NaOH for?
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elementcollector1
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NaOH - 7.99 per small canister
NaCl - .99 per a canister 1.5 times the size
H2O - 0
Electricity - technically 0
.99<7.99
As for what I want the NaOH for, it's mostly just having a good source of strong base, and I'm willing to wait quite a while between batches. I think
now that I have a good power supply (6A), I'll just use the two-beakers-and-a-wet-piece-of-paper method. Slower because of the insane resistances, but
hey, quality over quantity.
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barley81
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In my opinion, you'll have difficulty obtaining a pure product with that setup. Just buy the NaOH canister. $7.99 is not that much. You can order
large quantities online for a much lower price if you need that much. If you really want "quality over quantity" then you should buy NaOH that is
known to be pure instead of trying to separate out a little NaOH from NaCl solution mixed with sludge from electrodes, corroded paper bits, etc.
[Edited on 15-5-2012 by barley81]
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elementcollector1
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Sludge from electrodes? The last time I checked, cathodes don't disintegrate from hydrogen production. You're thinking of the anode, which is in a
separate cell.
Paper bits: These have to be much less soluble than NaOH itself, don't you think? Anyway, cellulose doesn't dissolve much, if at all in water.
This is a simple, cheap procedure that works well and leaves a pure product. Why wouldn't I consider it? It's not like I'm in any rush or anything...
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m1tanker78
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You also have to take into consideration the energy required to boil down and dry the product. You'll certainly have a lot of NaCl impurity in it too.
By the time the napkin works its magic, you'll have a solution of chloride, hydroxide, and carbonate/bicarbonate unless you exclude
CO2 somehow.
Red Devil lye is a thing of the past. It's no longer available except maybe old stock. With one exception, all commercial drain cleaners seem to
contain nitrate and aluminum bits. The one exception is Roebic but it's about $15 for a pound. It's not break-the-bank but still, for NaOH?...
Internet orders of NaOH aren't going to be a whole lot cheaper after S&H is factored in. I've taken some heat for this on this forum but I've
reacted sodium metal with water when I've needed small amounts of aqueous NaOH. It's so humid here; dry NaOH prills are very short-lived.
Tank
Chemical CURIOSITY KILLED THE CATalyst.
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elementcollector1
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NaCl impurity is largely eliminated by having the beaker with the cathode in a pure water solution. There will be some from the salt-soaked bridge,
sure, but I thought those ions would travel. Isn't that what the salt bridge is for?
Where does carbonate / bicarbonate come from, air? I know NaOH will absorb CO2 to form these, but I was under the assumption that this was a somewhat
slow process. If not, how do I exclude this impurity? (Thanks for warning me, by the way. I would not have expected this.)
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scatha
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I know a vendor here 25kg NaOH for 28 Euros - plus 6 euro postage - try to beat that ;D
However, love the reports about your experiments
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elementcollector1
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Yeah, that pure water thing failed. I need an inert electrolyte that I can remove easily, because pure water isn't doing much for conductivity. Should
I just use salt water in both half-cells and the ions will move from one cell to the other? I'll go try that and see if I get hydroxide or
hypochlorite...
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vmelkon
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Quote: Originally posted by elementcollector1  | | Yeah, that pure water thing failed. I need an inert electrolyte that I can remove easily, because pure water isn't doing much for conductivity. Should
I just use salt water in both half-cells and the ions will move from one cell to the other? I'll go try that and see if I get hydroxide or
hypochlorite... |
Are you referring to this? http://en.wikipedia.org/wiki/Chloralkali_process#Laboratory_...
I'm not an expert but is that a joke? One of the beakers with pure water? I can imagine that the salt will migrate to it slowly, but what is the point
of the beaker with pure water?
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elementcollector1
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For no impurities. It's worked before, it just starts slow and builds up quickly.
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