Th effect of inorganic anions on the dimerization constant of pyronine G in an aqueous solution was examined. It was found that the effect is very specific and can not be explained simply by the effect of the ionic strength. The analysis led to the conclusion that a dimer exists as an ion-pair with the anions attached laterally to dye ions instead of being sandwiched between two dye ions. The change of absorption spectra in the alkaline solution was interpreted to be due to the formation of carbinol, and from its analysis the formation constant of carbinol was determined. Carbinol was found to have also its proper fluorescence, and from the pH change of fluorescence spectra the formation constant of carbinol was again decided, the value of which coincided well with that obtained from the absorption spectra.