Mercury Vapor Rectifiers, they used to be used all over the place in industry.

Here's one being uncrated and tested after sitting crated for 50 years. https://www.youtube.com/watch?v=2pDcv6g1FE0

TIL

I'm guessing they won't be missed.

https://duckduckgo.com/?q=Mercury+vapor+turbine&t=fpas&ia=we...