2025-08-22
[public] 44.1K views, 5.15K likes, dislikes audio only
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In this video I'll explain different methods of producing metallic Sodium, and then make a bunch with electrolysis of molten Sodium Hydroxide (known as the Castner process). Sodium can be made by reacting NaOH with magnesium or aluminum, but the reaction is extremely fast and violent and it's difficult to contain the products. A more steady method is to reduce Sodium Carbonate with Carbon, which gives off Sodium Metal as vapor and Carbon Monoxide. The problem with this method is that it requires temperatures in excess of 800C, and a lot of the Sodium that's prouced reverts back to Sodium Carbonate when it contacts the Carbon Monoxide.
The other method(s) are to electrolyze molten salts. Industrially this is done by electrolysis of NaCl (the Downs process), but this also takes a very high temperature (at least 500C if a eutectic of NaCl and CaCl2 is used), and as I found when trying it in this video, the Sodium metal particles that are produced spontaneously ignite when they float to the top of the molten salt and contact the atmosphere, meaning that the cathode would need to be placed under inert atmosphere. The other problem with the Downs process is that the superheated Chlorine gas that's produced quick eats away the anode and creates an immensely potent smell even at just a few amps. Even operating it outdoors, the smell was intolerable.
So really the most practical method for small scale Sodium metal production is the electrolysis of molten NaOH. NaOH melts at 323C, which is a relatively easy temperature to reach with simple electric heaters. When NaOH is split, it makes metallic Sodium at the Cathode, and Oxygen and Water vapor at the Anode. In theory the water vapor should boil out, but in reality some of it gets diffused in the melt, which eventually causes problems as it reacts with the produced Sodium. For this reason, the cell needs to be occasionally stopped in order to have its temperature raised to drive off the accumulated moisture.
A PID temperature controller for the heater is required for this device, because Sodium is only produced in a narrow window between around 323C and 340C. Beyond 340C, the solubility of Sodium metal in the molten NaOH increases to the point that the yield becomes practically zero.
My end goal is to create a Sodium-Potassium eutectic alloy to have room-temperature liquid metal, so one possible change to this system might be to run a eutectic melt of NaOH and KOH which only requires 171C. This would be an easier temperature to maintain, and might also eliminate the possibility of the alkali metals dissolving back into the melt due to the much lower temperature involved.
In an 8 hour day, running the cell at 25A, I was able to collect a total of 36g of Sodium. With some improvements to the system, I think this amount could be significantly increased.
Finally, safety is paramount when dealing with molten NaOH. If stray water gets into the cell, it can cause a thermal explosion that splatters the melt all over the place. If molten NaOH contacts skin, it will rapidly burn and dissolve it away, possibly even more violently than sulfuric acid. I sustained a major injury for molten NaOH splatter while I was making this video, so I can speak from experience. For this reason, always use a face shield, long pants / sleeves, and long gloves when working near the stuff.
Research Sources:
https://patents.google.com/patent/US4276145A/en
Helpful guides I used:
https://www.youtube.com/watch?v=5slj-93PkxQ
https://www.metallab.net/Na.php
https://www.myttex.net/attachments/1002_Sodium%20metal.pdf
Music Used:
Kevin MacLeod - George Street Shuffle
Kevin MacLeod - Groove Groove