[lemma=storage] [tag=NNS] [!tag=IN] [lemma=pure] [□]
[lemma=storage] [tag=NNS] [!tag=IN] [lemma=pure] [□=□]
[lemma=storage] [tag=NNS] [!tag=IN] [lemma=pure] [□ & □]
Of potential practical hydrogen storage materials , pure Mg would be best from the standpoint of hydrogen capacity per unit mass .