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