Sometime back in the dim mists of history, when I was about 12 and already interested in things electronic, our 8th grade class took a field trip to the Ethyl Corporation plant in South Houston or Deer Park or some other industrial town/city in the Houston area.

I wasn't much interested at the beginning, because it was "look at this display vial, which has $SUBSTANCE in it." Yawn!

But then we got taken into the sodium refinery, and things got very interesting indeed.

Ethyl Corp. needed lots of pure sodium for one or more of the processes by which they produced tetraethyl lead, and had deemed it less expensive to refine their own than to buy it in enormous quantities from some other refiner. They used electrolysis of sodium chloride, common salt, which was and is available in enormous quantities from the salt domes which overlay many oil fields in Texas and Louisiana.

Refining sodium electrolytically requires huge electric currents; we were told to leave our watches in a building outside the sodium pot area because they would be magnetized and stop working.[1] I asked some questions, and found that the currents running through the molten salt in the cells were upwards of 1000 Amperes, and up to 5000 Amperes near the end of a batch process.

I don't know where they got their electric power, but the bill had to be sizable; neither do I know how they rectified it, though now I suspect it involved large mercury-arc rectifiers which must have been quite impressive in their own right. I wish I had asked. I am quite certain that their supplier was happy with the revenue: while they may not have used as much as, say, a 3-phase arc furnace, it still was sizable by any standard I've ever used.

The smell of chlorine was pervasive, there was a wonderfully strong contrabass HUMMMMMM at 60 Hz, and it was very obvious that Things Were Happening.

They don't make field trips like that any more, I'm told.

[1] This will give you an idea of how long ago it was.