Relay with mercury contact

> mercury relay with contacts able to withstand main line (230V) 2/4 A with isolation > 400V;

Why toxic Mercury??

400V 4A is not even a tough spec for a mechanical relay. In fact I would study an "air conditioning contactor". My A/C compressor relay (contactor) switches 240V 6 Amps many times a summer. Yes, it CAN burn-out, but can be replaced for $18 at the local warehouse or depot.

BTW, even people who still sell Mercury advise moving to Solid State, 2nd link below.

Mercury Relays and Contactors Wolf Automation
Solid State Relays vs Mercury Relays | Wolf Automation
Mercury Contactor Relays Nebraska Surplus
Mercury Contactor | Mercury Relay | Gordo Sales