counterionn.

1940 S. Glasstone Text-bk. Physical Chem. xiv. 1222 The..electrokinetic potential may be regarded as the effective potential at the ionic particle due to its own charge and to the opposing effect of the surrounding ‘counter-ions’ (or ‘gegen-ions’) which constitute the ionic atmosphere.

1949 Ann. N.Y. Acad. Sci. 51 843 In the chain polyelectrolyte..a microscopic test element will encounter wide fluctuations in charge density; between the positive polyions, it will contain only negative counter ions, while in the vicinity of the polyion it will contain both positive and negative ions.

1967 D. Margerison & G. C. East Introd. Polymer Chem. v. 243 It is the ions derived from these metals..which form the positive counterions to the growing polymer anions.

1978 P. W. Atkins Physical Chem. xi. 314 In the vicinity of any given ion there is a predominance of ions of opposite charge (these are called counter-ions)... On the average more counter-ions than like-ions pass by any given ion.

1981 M. Mandel in S. Krause Molecular Electro-Optics 285 Under well defined conditions the macromolecular chain carries a large number of charges (fixed charges) which are always accompanied in solution by an equivalent number of small ions of opposite sign (the counterions).

1986 Nucleic Acids Res. 14 1479 The three-dimensional Poisson-Boltzmann equation for the distribution of counterion charge density around double helical DNA has been solved.