The charge transfer bands of a betaine dye, 2,6-diphenyl-4-(2,4,6-triphenylpyridinio (1), and p-nitrophenoxide in solutions in acetonitrile are blue shifted in the presence of various concentrations of LiI. The shape of these bands changes with LiI concentration in a manner consistent with the formation of 1:1 complexes between the probes and Li+. The pi-->pi* region of the betaine spectrum is also altered by addition of LiI, and three isosbestic points appear when spectral intensities are made consistent with the association constant, K-LiB+ The spectra are most consistent with values of 3.3 x 10(4) and 5.5 x 10(4) M(-1) for K-LiP and K-LiB+, respectively. Conductance also supports the formation of a specifically bound lithium p-nitrophenoxide, K-LiP is larger by 3 powers of ten than the formation constant for the lithium iodide ion pair. These results illustrate the advantage of using a broad range of frequencies, spanning a large fraction of a spectroscopic band, in interpreting electronic spectra of solutions, rather than focusing on a small number of frequencies.