*B. Hribar and V. Vlachy*
*Faculty of Chemistry and Chemical Technology, University of Ljubljana,*
*Aškerčeva 5, 1000 Ljubljana, Slovenia.*

ABSTRACT

The Monte Carlo and integral equation results are presented for a primitive

model of a micellar solution. The macroions and small ions are modeled
as

charged hard spheres embedded in a continuous dielectric. The ratio
of di

ameters of the macroions and small ions (counterions and coions) is
3.0 nm

: 0.4 nm. The macroions are charged with 20 negative charges, the coions

have one negative charge, and the counterions may carry one or two
positive

charges. In a previous study of solutions containing macroions and
counterions

(B. Hribar and V. Vlachy, J. Phys. Chem. B, 1997, 101, 34573459) it
was

found that in solutions with monovalent counterions (20:+1) the macroions

were distributed at large distances from each other, while in solutions
with

divalent counterions (20:+2) the macroions shared the layer of counterions.

In the present paper the effects of addition of a simple electrolyte
to these

solutions are explored. For systems with monovalent counterions, addition

of a lowmolecular weight electrolyte causes the macroions to approach
each

other; the first peak of the pairdistribution function is shifted
toward smaller

distances. On the other hand, the solutions with divalent counterions
seem to

be less affected by addition of a simple electrolyte. The results for
the excess

internal energy, and osmotic coefficient for two different macroion
concentra

tions are presented in addition to the structural information.