▁due ▁to ▁the ▁same ▁cause ." ▁ ▁Joseph ▁Black ' s ▁" fixed ▁air " ▁During ▁ 1 7 7 3 ▁Lav ois ier ▁determined ▁to ▁review ▁thoroughly ▁the ▁literature ▁on ▁air , ▁particularly ▁" fixed ▁air ," ▁and ▁to ▁repeat ▁many ▁of ▁the ▁experiments ▁of ▁other ▁workers ▁in ▁the ▁field . ▁He ▁published ▁an ▁account ▁of ▁this ▁review ▁in ▁ 1 7 7 4 ▁in ▁a ▁book ▁entitled ▁Op us cules ▁phys iques ▁et ▁chim iques ▁( Phys ical ▁and ▁Chem ical ▁Ess ays ). ▁In ▁the ▁course ▁of ▁this ▁review , ▁he ▁made ▁his ▁first ▁full ▁study ▁of ▁the ▁work ▁of ▁Joseph ▁Black , ▁the ▁Scottish ▁chem ist ▁who ▁had ▁carried ▁out ▁a ▁series ▁of ▁classic ▁quant itative ▁experiments ▁on ▁the ▁m ild ▁and ▁ca ust ic ▁al kal ies . ▁Black ▁had ▁shown ▁that ▁the ▁difference ▁between ▁a ▁m ild ▁alk ali , ▁for ▁example , ▁ch alk ▁( Ca CO 3 ), ▁and ▁the ▁ca ust ic ▁form , ▁for ▁example , ▁quick lime ▁( Ca O ), ▁lay ▁in ▁the ▁fact ▁that ▁the ▁former ▁contained ▁" fixed ▁air ," ▁not ▁common ▁air ▁fixed ▁in ▁the ▁ch alk , ▁but ▁a ▁distinct ▁chemical ▁species , ▁now ▁understood ▁to ▁be ▁carbon ▁dio x ide ▁( CO 2 ), ▁which ▁was ▁a ▁constitu ent ▁of ▁the ▁atmosphere . ▁Lav ois ier ▁recognized ▁that ▁Black ' s ▁fixed ▁air ▁was ▁identical ▁with ▁the ▁air ▁evol ved ▁when ▁metal ▁cal ces ▁were ▁reduced ▁with ▁char co al ▁and ▁even ▁suggested ▁that ▁the ▁air