Aq. solns. of 4-(5-heptyl-1,3,4-thiadiazo-2-yl)benzene-1,3-diol (C7) showed two well-resolved fluorescence bands at 20-40 degrees C and pH 1-7. At the temps. exceeding 40 degrees C, only a single fluorescence max. was obsd. The resonance light scattering spectra measured at 20-40 degrees C showed a strong signal, which decreased with the temp. increase. The data were consistent with previous reports and confirmed a moL aggregation-related nature of the fluorescence effects. The possibility of a quick fluorescence spectro-scopy-based anal. of infra- and intermoL transformations was evidenced.