( Empedocles ( ( ( discovered air ) ( as ( a ( separate substance ) ) ) ) . ) )
(ROOT (S (NP (NNS Empedocles)) (VP (VBD discovered) (NP (NN air)) (PP (IN as) (NP (DT a) (JJ separate) (NN substance)))) (. .)))
Empedocles discovered air as a separate substance.
(ROOT (S (NP (NNP Air)) (VP (MD can) (VP (VB be) (VP (VBN separated) (PP (IN into) (NP (JJ several) (NNS elements)))))) (. .)))