Editing Mercury switch (section)

==Disadvantages==
Mercury switches have several disadvantages:
* There is a tendency for the intermittently exposed electrode to become damaged by the intense heat and destructive force of the electrical arc that forms whenever the circuit opens or closes, particularly if the circuit is being opened under a large inductive load.  Certain refractory materials have been used to encase this electrode to mitigate this effect.
* Their relatively slow operating rate (due to the inertia of the mercury drop) makes them unsuitable for applications that require many operating cycles per second.<ref>David W. Pessen, ''Industrial automation: circuit design and components'', Wiley-IEEE, 1989 {{ISBN|0-471-60071-7}}, page 44</ref>  
* Glass envelopes and wire electrodes may be fragile and require flexible leads to prevent damage to the envelope. 
* The mercury drop forms a common electrode, so circuits are not isolated from each other in a multi-pole switch.
* Their sensitivity to gravity may make them unsuitable in portable or mobile devices that can change orientation or vibrate. 
* Mercury compounds are [[#Toxicity|highly toxic]] and accumulate in any [[food chain]], so safety codes exclude mercury in many new designs.