( ( If ( ( mercury compounds ) ( are ( used ( as catalysts ) ) ) ) ) ( , ( ( an alternative ) ( ( is ( to ( ( ( simply ( eliminate ( the catalyst ) ) ) and ) ( ( let ( the ( reaction run ) ) ) longer ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN If) (S (NP (NN mercury) (NNS compounds)) (VP (VBP are) (VP (VBN used) (PP (IN as) (NP (NNS catalysts))))))) (, ,) (NP (DT an) (NN alternative)) (VP (VBZ is) (S (VP (TO to) (VP (VP (ADVP (RB simply)) (VB eliminate) (NP (DT the) (NN catalyst))) (CC and) (VP (VB let) (NP (DT the) (NN reaction) (NN run)) (ADVP (RBR longer))))))) (. .)))
If mercury compounds are used as catalysts, an alternative is to simply eliminate the catalyst and let the reaction run longer.
(ROOT (S (SBAR (IN If) (S (NP (DT a) (NN catalyst)) (VP (VBZ runs) (PRT (RP out))))) (, ,) (NP (DT the) (NN reaction)) (VP (VBZ slows)) (. .)))