▁used ▁to ▁measure ▁high ▁temper atures . ▁A ▁still ▁increasing ▁amount ▁is ▁used ▁as ▁g ase ous ▁mer cur y ▁in ▁flu ores cent ▁l amps , ▁ ▁while ▁most ▁of ▁the ▁other ▁applications ▁are ▁slowly ▁ph ased ▁out ▁due ▁to ▁health ▁and ▁safety ▁reg ulations , ▁and ▁is ▁in ▁some ▁applications ▁replaced ▁with ▁less ▁to xic ▁but ▁consider ably ▁more ▁expensive ▁Gal inst an ▁al loy . ▁Mercur y ▁and ▁its ▁comp ounds ▁have ▁been ▁used ▁in ▁medicine , ▁although ▁they ▁are ▁much ▁less ▁common ▁today ▁than ▁they ▁once ▁were , ▁now ▁that ▁the ▁to xic ▁effects ▁of ▁mer cur y ▁and ▁its ▁comp ounds ▁are ▁more ▁widely ▁understood . ▁It ▁is ▁still ▁used ▁as ▁an ▁ing red ient ▁in ▁dent al ▁am alg ams . ▁In ▁the ▁late ▁ 2 0 th ▁century ▁the ▁largest ▁use ▁of ▁mer cur y ▁was ▁in ▁the ▁mer cur y ▁cell ▁process ▁( also ▁called ▁the ▁Cast ner - K ell ner ▁process ) ▁in ▁the ▁production ▁of ▁ch lor ine ▁and ▁ca ust ic ▁s oda . ▁ ▁Bi ological ▁role ▁and ▁to x icity ▁The ▁group ▁ 1 2 ▁elements ▁have ▁multiple ▁effects ▁on ▁bi ological ▁organ isms ▁as ▁cad m ium ▁and ▁mer cur y ▁are ▁to xic ▁while ▁z inc ▁is ▁required ▁by ▁most ▁plants ▁and ▁animals ▁in ▁trace ▁amounts . ▁ ▁Z inc ▁is ▁an ▁essential ▁trace ▁element , ▁necessary ▁for ▁plants , ▁animals , ▁and ▁micro organ isms . ▁It ▁is ▁" typ ically ▁the ▁second ▁most ▁abund ant