negative colloids ( collodion , mastic , acheson 's graphite , gold , and metal proteinates ) are rendered more negative by low concentrations of salts with monovalent cation ( e.g . na ) the higher the valency of the anion , though the difference in the maximal p.d . is slight for the monovalent cl and the tetravalent fe ( cn ) ( 6 ) ions .
C0003075
anion
C0022023
ions