a method for removal of oxygen dissolved in water , especially from reservoir drinking water , and for preservation purposes based on hydrazine , having no organic activators and assuring a high reaction velocity with respect to dissolved oxygen within a broad ph - range at low temperature and without a time - dependent reduction of its effectiveness . cationic and anionic complexes of trivalent cobalt with inorganic ligands , or mixtures thereof , are used as activators . preferred activators are 5 cl ) cl 2 and na 3 co 6 . hydrazine solutions with these activators are suitable for the removal of oxygen from gases .