VOLUME 2 2, NO. 1, JANUARY 1950 33 the quinoline molecule (47). This behavior of 8-hydroxyquinoline has been made the basis of a method for determining aluminum.The aluminum is precipitated with 8-hydroxyquinoline and the excess reagent used is determined polarographically (SO).Quinoline-8-carboxylic acid has been studied in buffers ranging from pH 1 to 12 and behaves like 8-hydroxyquinoline in that three waves are obtained (48). Determination of Metals. The addition of 2-naphthol, thymol, and diphenylamine changes the diffusion current and shifts the half-wave potentials of metallic ions. This behavior is ascribed to adsorbed films upon the electrode (19).