Aquated cations group

FIGURE 23 The structure of [Bi2W22076]14 as an assembly of four W06 octahedra sandwiched by (B-/S-BiW9033) groups. The arrows identify the binding sites of aquated Eu3" " cations that link the polytungstates into a 3-D network [Eu3(H20)i8(Bi2W22076)]5 x. 

Neither gold(i) nor gold(lll) forms a stable aquated ion ([Au(OH2)2 4 ] or [Au(OH2)4 ], respectively) analogous to those found for many transition metal and main group cations. Both are thermodynamically unstable with respect to elemental gold and can be readily reduced ... 

Examples of cationic polymers include polymers with phosphonium, sulfo-nium, and ammonium groups. Polymers that are reasonably anticipated to become cationic in the natural aquatic environment, such as in rivers and streams, are also excluded, and this includes polymers with amine or isocyanate groups. 

With regard to bioconcentration, it is important that surfactants are characterized by combining a lipophilic and a hydrophilic moiety in the same molecule. This is true for all four classes, namely anionic, nonionic, cationic and amphoteric surfactants. Although these classes possess quite different hydrophilic groups, the lipophilic part usually consists of an alkyl chain or alkyl chains of different lengths. There is some evidence that the lipophilic groups of surfactants are metabolized after uptake by aquatic invertebrate species (Daphnia and Chironomus) and fish. 

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