ell onian ▁University , ▁Est reich er ▁worked ▁as ▁an ▁assistant ▁to ▁Kar ol ▁O ls zew ski , ▁the ▁first ▁chem ist ▁to ▁li que f y ▁o xygen . ▁After ▁having ▁been ▁appointed ▁assistant ▁in ▁ 1 8 9 9 , ▁Est reich er ▁successfully ▁li que f ied ▁hydro gen ▁in ▁ 1 9 0 1 ▁before ▁he ▁was ▁promoted ▁to ▁Priv at do zent ▁in ▁ 1 9 0 4 . ▁ ▁In ▁ 1 9 0 0 , ▁he ▁described ▁the ▁J agi ell onian ▁glo be ▁in ▁the ▁Trans actions ▁of ▁the ▁C rac ow ▁Academy ▁of ▁Sciences . ▁ ▁From ▁ 1 9 0 6 ▁until ▁ 1 9 1 9 ▁he ▁worked ▁in ▁Switzerland ▁a ▁professor ▁for ▁min eral ▁and ▁general ▁chem istry ▁at ▁the ▁University ▁of ▁F rib ourg ▁where ▁he ▁ran ▁a ▁cry ogen ics ▁labor atory . ▁From ▁ 1 9 1 3 ▁to ▁ 1 9 1 4 ▁he ▁also ▁served ▁as ▁de an ▁of ▁the ▁department . ▁ ▁In ▁ 1 9 1 9 , ▁aged ▁ 4 7 , ▁he ▁returned ▁to ▁newly ▁independent ▁Poland ▁and ▁took ▁a ▁position ▁with ▁the ▁J agi ell onian ▁University ▁where ▁he ▁remained ▁until ▁his ▁ret irement . ▁His ▁later ▁work ▁exam ined ▁the ▁history ▁and ▁language ▁of ▁science . ▁ ▁On ▁ 6 ▁November ▁ 1 9 3 9 , ▁along ▁with ▁his ▁brother ▁Stanisław ▁and ▁other ▁profess ors ▁of ▁the ▁University , ▁Est reich er ▁was ▁caught ▁in ▁Son der akt