Ion added

Tolerance ratio (w_ion/w_Cu(II))

K⁺, Li⁺, Na⁺, succenate, acetate, tartaric acid

15000^a

Ag⁺, Ba²⁺, Ca²⁺, oxalic acid, C₂O₄^2-

12000

Ba²⁺, Ca²⁺, Mg²⁺, S, Sr²⁺, I^-, Br^-, B(III),

10000

Al³⁺, Cr³⁺, SO₄^2-, PO₄^3-, F^-

8750

Sn(IV), V(V), Cl^-, NO₃^-

7000

Co²⁺, Cd²⁺, borate, hydrazine,

5500

La³⁺, Y³⁺, Sc³⁺, Br^-, hydrazine

4000

Fe²⁺, Hg²⁺, ClO₃^-

2500

Mn²⁺, Zn²⁺, SCN^-, SO₃^2-

1250

Mo(V), Sb(III), thiourea

750

Fe³⁺, NO₂^-

400