A platinum electrode, a Radelkis OP-C-7111D graphite electrode and a laboratory-prepared silicone-rubber-based membrane graphite electrode were used in potentiometric titrations of reducing substances with bromine in acetic acid. In determinations of hydroquinone, 2-methylhydroquinone, 2-chlorohydroquinone and ascorbic acid, the Radelkis electrode showed the greatest sensitivity. The advantage of the laboratory-prepared membrane graphite electrode lay in its rapid attainment of stable potential values. Titrations were improved by addition of potassium acetate to the solutions analysed. The effects of water and acetic anhydride on the results were also investigated.