The reaction of 18-crown-6 with aqueous iodine has been monitored by U
V and visible spectrophotometry. The stability constant for the reacti
on has been determined as well as the spectra for the pure aqueous com
plex. This stability constant has been related to other equilibrium co
nstants for the complexation of molecular iodine. The relation appears
to predict correctly the stability constant for the iodine-water char
ge-transfer complex.