1.With the aid of polarography a study was made of the tautomeric and stereoisomeric transformations of the phenylhydrazones of acetophenone, 4′-chloroacetophenone, acetaldehyde, and isobutyraldehyde in alcoholic solutions.2.In a freshly prepared solution the phenylhydrazones of acetophenone, 4′-chloroacetophenone, and benzaldehyde have hydrazone structures, which appear to be their structures in the free state. In the free state the phenylhydrazones of acetaldehyde and isobutyraldehyde probably also have the hydrazone structure, but on dissolution in alcohol they pass into the ene-hydrazine structure, which is probably in equilibrium with the other tautomeric forms.3.The potentials of the half-waves of the tautomers and stereoisomers of the compounds studied were determined, and from these the energies of mutual transitions were calcula