550Recently, the creation of new metal oxide, in par ticular, metal oxide film electrodes (MOFE) and com prehensive studies of the available ones has offered a promising direction in the development of electroana lyical sensors because of the low cost of the new elec trodes as compared to noble metal electrodes, and easiness of work with them.The ruthenium-titanium oxide anode (RTOA) characterized by high corrosion stability, the stability of electrochemical parameters within long operation times, and high selectivity provides an example of MOFE. RTOA is extensively used in applied electro chemistry, first of all, in chlorine and sodium hydrox ide production, in the synthesis of sodium hypochlo rite by the electrochemical method, seawater electrol ysis, etc. [1][2][3][4][5]. At present, RTOAs, including those modified by different elements, are used as sensors in different methods of electrochemical analysis [6][7][8]. It was demonstrated in [6] that the RuO 2 -Ti electrode is a highly sensitive and easy to operate sensor for pH detection, with the slope of the pH function 56.03 mV/pH and, simultaneously, insensitive to the presence of Li + , Na + , and Ca 2+ ions.A Ni-RuO 2 electrode was used as an indicator electrode for the voltammetric determination of ethanol [8] and the evaluation of the acid number of oils [7].Ni/P composites on titanium(IV) oxide with nano additives of RuO 2 [9] were used for the amperometric determination of ethanol in 0.2 M NaOH.Electrodes comprising film coatings on a titanium substrate with different amounts of Ti(IV), Ru(IV), and Sb(III) oxides were investigated [10], and their linear Е-рН dependence with a higher slope ratio as compared to the theoretical one was demonstrated.In the present work, the behavior of RTOA in the absence of polarization and in potentiometric titration by different reaction types was studied. In the revela tion of the indicator properties, the mechanism of the reaction determining the electrode potential was investigated by a number of methods (constructing kinetic, concentration, and voltamperometric curves).
EXPERIMENTALThe MOFE consisted of titanium plates of the VT 1 0 grade (2.5 × 0.5 × 0.1 cm 3 ) with a deposited active layer of titanium and ruthenium oxides in the ratio 30 : 70 mol %.Prior to depositing the active layer, titanium plates were kept for 5 min in hot conc. HCl, then for 20 min in a saturated С 2 Н 2 О 4 solution, and then washed in distilled water. The active layer was deposited on the thus prepared titanium plates by the thermal decom position of a mixture of ruthenium hydroxochloride and titanium chloride according to [11].Potentiometric measurements were carried out on a portable Radelkis OP 265/1 ion and pH meter. The Radelkis OP 0830P calomel electrode served as a reference electrode. An automated Radelkis ОР 930/1 burette was used for titration measure ments.Voltammograms were recorded on a Radelkis ОН 105 polarograph. A two electrode cell consisting of a working electrode and a silver-silver chloride ref erence electrode was used...