Mercuric sulfate: ORAL (LD50): Acute: 57 mg/kg [Rat]. DERMAL (LD50): Acute: 625mg/kg [Rat]
Mercury: The LD50 values in animals for elemental mercury range from 10 to 40 mg/kg (WHO 1976)
That's the best info I could find.. Mercuric sulfate was easy, but I had a lot of trouble finding plain Mercury.