Wow.
Mercury arc valves remain in use in some South African mines and Kenya (at Mombasa Polytechnic - Electrical & Electronic department).
Amazing how we’re still using such old technology in some places when we have semiconductors.
Wellington turned off the last mercury arc rectifiers in its electric commuter rail about 2010.
Plenty of heritage tramways and historic railways still use them. Polytechs keep all kinds of long obsolete equipment running for training purposes too - one, there’s still a need for people to operate/maintain it, and two, older gear can sometimes be good as learning tools due to simplicity. That doesn’t really apply to diodes vs mercury arc though…
They were the only practical option to get DC from AC until maybe the 60s, and they’re pretty bulletproof. They’re usually replaced because of upgrades, not failure/obsolescence.
