A very simple square wave polarograph is easily constructed by attaching two vibratots to the Heyrovsky-Shikata Polarograph (type V301).This "vibrator square wave polarograph" was first advocated by Kiang I-Chin and modified by Feng Chiang-Shing et al.The present authors introduce some innovations in the circuit so as to render the waves more stable and reproducible.The polarograph is very simple in construction,but quite sensitive.For reversibly-reduced ions (e.g.Cd²⁺ in 0.1 M KCl),2×10^-7M can be detected and the optimum concentration range for determination is 10^-4-10^-6 M.This apparatus is especially suitable for teaching purpose.