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View Full Version : Sodium metal, (very) small-scale production



theFool
05-06-2013, 01:39 PM
Sodium metal can be made by electrolysis of molten sodium hydroxide which has a low melting point (318 deg) which can be reached easily. It is important to use a nickel crucible for this job because molten sodium hydroxide will eat almost all kind of metals and those will contaminate and interfere with the process.

http://i81.servimg.com/u/f81/13/27/64/97/na110.jpg

Here the crucible with molten NaOH (appears black) in it. (plus a small explosion!). The temperature of the molten sodium should be just above its melting point, if it is much hotter, the sodium produced will disintegrate/react much more easily.
The positive terminal of a 15V/3A source is connected directly onto the crucible. This forms the anode, where oxygen will evolve. The other terminal (negative) is connected to a copper wire which has a small loop at the edge:

http://i81.servimg.com/u/f81/13/27/64/97/na210.jpg

When this copper wire touches the molten NaOH, sodium metal is produced and it sticks itself into this small loop. Unfortunatelly, if you leave the electrolysis to run for a long time, you will not get more sodium than the one that can stick in this loop. Oxygen produced at the anode reacts with it and it burns. So the method consists of inserting the loop in the molten NaOH, removing the sodium metal and repeating again and again.

Removing sodium from the loop:
This is not easy. A small beaker is filled with 2-3 mm of water and on top of it ample petroleum oil is poured. The loop with the sodium metal is quickly dipped in to the beaker touching the water at the bottom. The sodium reacts and frees itself from the loop. It is lighter than water and so it rises up into the oil phase where it can be safely collected and stored under mineral oil.

In general, sodium metal (when it is in greater volume than those globules) should not touch water because it explodes. Explosions during electrolysis also are very common because of some sodium metal escaping the loop. They can throw molten NaOH on the face/skin, so full body protection is required. Also there is the danger of the molten lye spilling out of the crucible if it is not securely fitted on top of the burner.

Anyway, it is a dangerous experiment.

Nibiru
05-08-2013, 04:06 PM
This could be quite useful, I wonder if it works for other metals like magnesium and calcium as well? Thank you very much for sharing!!!

theFool
05-08-2013, 04:24 PM
This could be quite useful, I wonder if it works for other metals like magnesium and calcium as well? Thank you very much for sharing!!!
Thanks Nibiru. In theory it works with other metals also .. but: Calcium salts have a very high melting point, impractical to reach easily. I also know that potassium metal requires oxygen free atmosphere in order to be collected as a metal (or else, it burns). I don't know much about magnesium, in industry they make it by electrolyzing molten magnesium chloride. I guess if someone gets to sodium, he can use this to acquire other metals too (but this would be a waste of sodium).