doc - 14-12-2012 at 15:11
Hello
I found couple of kgs of mercury and decided I will do my own electrocell, which will be able to produce sodium amalgam in continuous operation,
ideally about 100grams per hour.
I know a quite a bit about chemistry but I must admit I never showed much interest in electricity - so I will have to do better reaserch now.
100 grams per hour means 100/23 = 4.35 mol of sodium per hour. That further means 408.132 As and if I want to produce that in an hour that needs
current 113A if "yield" is 100% (which in reality isnt, more like 30%?)
Cathode: Mercury
Anode: Nickel
Can someone advice what surface should electrodes have? I figured that current would best be achieved with welding machine. What kind of voltage would
be most appropriate?
So the plan is to have 40% NaOH solution. Here is a good picture of process (only this uses NaCl)
http://www.eurochlor.org/the-chlorine-universe/how-is-chlori...
Has anyone done this allready? Sodium amalgam would be used for reductions or for making MeONa or EtONa.
So the question is, how can I calculate size of electrodes?
What voltage is needed? (calculation)
If this is continuous operation, how to assure that pump (peristaltic one) wont be under same voltage/current? This might be a stupid question for
some 
I will firstly build much smaller scale for test runs but would like to know what is needed for larger one.
bfesser - 14-12-2012 at 16:49
This sounds like a horrifically bad idea. You're going to be pumping around liquid Hg, in contact with numerous other metals, and you're going to be
performing aqueous electrochemistry in this environment? You're going to develop a nightmare of Hg contamination. Are you prepared to deal with the
hazards and responsibilities presented by processing, handling, and storing alkali-metal amalgams? What tubing material are you going to use in the
peristaltic pump? Will it be degraded or otherwise effected by acid, base, Hg, Cl<sub>2</sub>, H<sub>2</sub>? Do you realize
that the evolved gases will invariably be 'contaminated' with Hg vapor?
Arsole - 14-12-2012 at 19:16
I can't even think of one good reason why you should try this at that scale.
Have you done Amalgamations before?
My advice, first demonstrate a smaller scale like you suggested and work out the kinks.
3 scenarios for small scale.
1. It works and you feel comfortable: move on to a more ambitious scale.
2. It works and you realize larger is not a good idea: Good job you earned a beer.
3. It didn't work: Try again or pick a new project.
If you find you were poisoned you might as well go balls out and go as large as possible as you are probably screwed anyway. The rest of us might
learn something. (Actually I guess this would be the good reason to try it at that scale)
Why do you need Kg's of sodium amalgam? Besides the cool factor. 
BromicAcid - 14-12-2012 at 20:22
Off the top of my head, this can be done with a solid block of KOH or NaOH instead of aqueous solutions which could lead to widespread mercury
contamination. Also of note is that the solid amalgam actually only has a small % of sodium in it, a quick Wiki search says at 2% the amalgam is
solid, you will not get a lot of sodium from your solution before it solidifies. Remember that the usual method of recovery of sodium from mercury
amalgam (if that is your hope) is distillation (which with mercury could be a potential disaster). Finally, you have some quick number crunching in
your initial post regarding current and yields. Note that you only make sodium due to the overpotential generated by using the mercury, you will not
be effectively making your sodium at theoretical levels and will lose efficiency to general electrolysis of water and back reaction of your sodium
with you water.
doc - 15-12-2012 at 00:22
If they did this pre-1900 and it was for a long time main method for producing Cl2 and NaOH, how bad can it be? http://en.wikipedia.org/wiki/Castner-Kellner_process
I am aware of Hg danger. This would be done in well ventilated area with carbon filters to preven contamination. Never would mercury be evaporated
cause there isnt need for pure sodium, just amalgam, which can be put into dry alchocol to produce methoxide/ethoxide.
As I see it, anode will be producing water and oxigen. No hydrogen od chlorine will be produced, since 40% NaOH is used not NaCl (just for that
reason).
2OH- ---> H2O + 1/2O2
Tubing? LDPE or something similar. As for the 2% beeing solid - this is why proces is continuous - so the sodium is used immediately for whatever
purpose and "empty" Hg is pumped back into the cell.
Anyway, if someone can help with electrical part would be much appreciated. Real life voltage, amps, electrodes. How much heat will be produced and
anything else
[Edited on 15-12-2012 by doc]
smaerd - 15-12-2012 at 06:49
Honestly, if you can't figure out the electrical conditions on your own, how do you plan to trouble shoot? I guarantee there are published conditions
for this which you should seek out in scientific literature, or maybe even patent literature as this is an old industrial process.
What on earth do you need 100 grams of sodium amalgam an hour for? You want to make methoxide/ethoxide, there are easier ways. Would it really deter
you to not have currents high enough that in the probable case of injury or mistake the end result would not be fatal. How do you plan to cool the
vessel? Running 110 amps into something will definitely make it hot, really hot, keeping in mind mercury is a volatile liquid at room temperature.
Like you said that kind of current is typically used in welding metal to metal... Definitely do this small scale so you can understand just what you
are actually getting yourself in to.
Think about this really quick. if it's a continuous process and you somehow could nail it down to say 0.5mol an hour, that's still a huge yield. In
two hours you could have enough reagent to reduce a mole of a compound. That's a very large scale reaction...
As far as electrodes I would use graphite or glassy carbon, to prevent metal contamination of the mercury Ie: Other metal amalgams. These will need to
be replaced from time to time if they work. Electrode size, shape, and distance apart, depends on a lot of factors. If you want a more firm
theoretical grasp on some of the principles in electro-chemistry I suggest reading through some of the topics on this web-site.
http://electrochem.cwru.edu/encycl/art-a03-analytical.htm#ap...
http://electrochem.cwru.edu/encycl/art-d03-curr-distr.htm
Here's a journal article to get you started:
Electrolytic Preparation of Sodium Amalgam
E. S. Shepherd
The Journal of Physical Chemistry 1902 7 (1), 29-30
doc - 15-12-2012 at 10:58
Well this is why I would do small scale first. But any advice/imput on large scale would be nice, since its allways easyer to scale it down than it is
to scale it up.
As for electrodes, I did find one patent a while back, saying most appropriate materials are mercury cathode and nickel anode. Graphite corrodes too
extensively, others are too expensive. But that still leaves with a choice for cathode, since u cant apply current directly to mercury. Perhaps if
cell was stainless steal, isolated everywhere but on bottom, where it comes in contact with mercury. And it should not make amalgam. But what concerns
me is when amalgam comes out of the cell, it will still be under voltage/current when going into pump. How to prevent that.
As for the test vessel, it will be prob around 4.5A and 12V. That should keep me alive. Tnx for links.
Swede - 21-12-2012 at 06:35
You can energize mercury with a glass-encased conductor that comes from the top and penetrates into the pool of mercury.
Like a copper wire inside a glass pipette.
[Edited on 21-12-2012 by Swede]
Sodium manufacture. Electrolytic cell.
FrankMartin - 11-2-2013 at 18:53
A good laboratory prep of Sodium metal is described in:
"SMALL-SCALE SYNTHESIS
of LABORATORY REAGENTS
with Reaction Modeling"
CRC Press
Taylor & Francis Group
6000 Broken Sound Parkway NW, Suite 300
Boca Raton, FL 33487-2742
© 2011 by Taylor and Francis Group, LLC
CRC Press is an imprint of Taylor & Francis Group, an Informa business
International Standard Book Number: 978-1-4398-1312-6 (Hardback)
Also K, Li, Br, Cs etc.