The only cobalt complex which is formed at pH's 6–8 is soluble and has the composition [Co 2 III (SAO) 3 ] 0 . With nickel, an insoluble complex [Ni(SAO) 2 ] 0 is formed quantitatively between pH = 6 ⩽ 12. At pH ≥ 12 it is abruptly and completely transformed into the soluble complex [Ni(SAO) 2 2− . K = [Ni 2+ ] [SAO] 2 /[Ni(SAO) 2 −2 ] = 6·4 × 10 −5 . With copper, the insoluble complex [Cu(SAO) 2 ] 0 is quantitavely formed between pH 3–10, and it is completely and abruptly transformed into [Cu(SAO) 2 ] 2− which is soluble, at pH ≥ 11. K = [Cu 2+ ] [SAO 2− ] 2 /[Cu(SAO) 2 −2 ] = 6·4 × 10 −5 . Ammonia does not interfere with the soluble complexes.
