The electronic absorption spectra of some hydroxamic acid oxime derivatives and Schiff's base derivatives in polar (ethanol) and nonpolar (CCl4) solvents, as well as in some other organic solvents of different polarities, were investigated; the variation of absorbance with pH was utilized for the determination of pKa, and Δ G* values. The important bands in the IR spectra as well as the main signals of the NMR spectra are also discussed in relation to the molecular structure.