The polarographic behavior of trans-stilbene, triphenylethylene, tetraphenylethylene, benzyl chloride and carbon tetrachloride has been studied in tetramethylurea containing tetrabutylammonium bromide. The results obtained indicate that this solvent offers no advantage over dimethylformamide. The high resistance of the solvent made the large scale electrolysis of benzyl chloride difficult to carry out. Products obtained were toluene, n-butane, butenes and tri-n-butylamine. The similarity in structure of tetramethylurea to dimethylformamide suggested an evaluation of this liquid as a solvent for the polarographic studies of organic compounds. Studies in the latter have furnished evidence for the existence of stable anion-free radicals in the reduction of aromatic hydrocarbons, quinones, aromatic ketones and of dihalocarbenes in the reduction of carbon tetrachloride and bromide.

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The polarographic reduction of benzophnone at the dropping mercury electrode has been investigated in 20% to 100% pyridine solution with particular attention to the nature of the electrolytic process in dry pyridine. In the latter solvent, benzophenone is reduced in an apparently one-electron reversible process to an anion free radical, which would readily dimerize to a product, which would in turn hydrolyze in the presence of water to form benzpinacol. The reduction mechanism is thus generally similar to that of benzophenone in alkaline aqueous solution, where the relative lack of hydrogen ion results in an anionic free radical being the primary product.

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An increasing interest for natural and synthetic aldehydes and ketones has caused that a significant number of analytical papers on this subject was recently published. Until now some specific reactions of individual compounds were used in the classical organic analysis''. Addehydes were also determined using some instrumental methods, e.g. polarography2'. All these methods are non-selective and cannot be used in investigation of mixtures. Recently adsorption chromatography, partition chromatography on carrier and paper, ion-exchange chromatography and gas-liquid chromatography were used for separation of aldehydes and ketones. Attempts were made to separate these compounds as their derivatives, viz. semicarbazones, hydroxamic acid derivatives, but highly promising results were obtained using 2, 4-dinitrophenyihydrazones. This procedure has been described by many authors, who applied, among others, also reverse phase partition chromatography In this paper the chromato-polarographic method was used for the analysis of mixture of aldehydes and ketones. The chromato-polarographic method may be used for the study of species reducible at the mercury dropping electrode over the potential range, which is not too negative. Otherwise, either some indirect methods should be used", '2', or, with usually better result the polarographically inactive compounds should be transformed into reducible ones. Quantitative formation of stronly coloured, insoluble precipitates of 2, 4-dinitrophenylhydrazones of carbonyl compounds enables application of colorimetric or polaro* graphic methods to the determination of aldehydes and ketones. Nevertheless both mentioned methods are poor in selectivity and cannot be used for the analysis of mixtures of mentioned compounds.

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Der EinfluB der Tropfzeit auf die polarographische Stromstärke liefert bekanntlich einen mitunter wertvollen Einblick in die Art des Elektrodenvorganges. Bei diesbezüglichen experimentellen Untersuchungen wird die Tropfzeit im allgemeinen durch Änderung des Quecksilberdruckes variiert. Es ist aber auch möglich, die Tropfzeit durch Abschlagen des Tropfens zu ändern. Durch reguliertes Abschlagen ist es leicht möglich, eine Tropfzeit von z.B. 5 sec auf 0, 2 sec herabzusetzen, entsprechend einer Variation um den Faktor 25. Durch Änderung des Quecksilberdruckes ist emn so groBer Bereich nicht zugänglich, da extreme Hg-Drucke Störungen bedingen: Bei zu groBen Drucken bewirkt der heftige QuecksilberzufluB störende Ströanungen im Tropfen (Maxima 2. Art), bei zu kleinem Druck wird der Rückdruck des Quecksilbertropfens störend. Wir haben daher Versuche unternommen, um die Brauchbarkeit der Tropfzeitvariation durch Abklopfen zu prufen.

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It is suggested that the experimental arrangement for alternating current polarography becomes more convenient if the alternating current is controlled and the alternating voltage measured, the converse of the traditional procedure. Experimental requirements are discussed; the technique offers advantages in routine a.c. polarographic work, in phase-angle measurement and in the study of rectification effects.

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It was like in an old fairy tale: When Professors J. Heyrovský and M. Shikata parted, each brought a problem with him home : There were mainly inorganic problems studied in Czechoslovakia whereas much stress has been laid on organic polarography in Japan. This division even when not without notable exceptions remained until early forties. It is thus not surprising that it was from the pen of M. Shikata and I. Tachi from which the first papers on correlations between the structure and polarography of organic substances appeared. The famous Shikata-Tachi rule was a guide of organic polarographers for almost two decades, basing on the qualitative knowledge of theoretical organic chemistry of these days.Since then organic polarography broadened considerably its scope and also the understanding of the electrode processes got more profound. Japanese scientists joint in this venture and helped to our understanding of the polarographic behaviour of organic substances. Professor I. Tachi and his coworkers contributed substantially in this respect. When the quantitative treatment of structural effects was developed, polarography applied such methods to the treatment of half-wave potentials. Again Japanese chemists took part in that development (cff the references later in the text part). Thus it is a great priviledge to contribute to the volume devoted to Professor I. Tachi in the field he himself fostered. In addition to rate and equilibrium constants, for which these relationships were originally devised, several physico-chemical quantities were correlated using Hammett and Taft equation and similar free energy relationships. Whereas for most other physico-chemical quantities, like the wave-length of the maximum of a selected band in UV-spectra or like quadrupole coupling constants, these correlations are at present purely empirical, for polarographic half-wave potentials the explanation for such correlations between electrochemical data and equilibrium and kinetic data (expressed through the values of the substituent c constants) can be suggested.

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Principles, theory and methodology are discussed for the applications of the coulostatic method toanalytical chemistry, electrode kinetics and adsorption kinetics. The coulostatic method is based on the following principle: a known quantity ofelectricity is supplied to the working electrode of an electrochemical cell in a very short time (perhaps l microsecond or even a shorter time), and the subsequent variations of potential of the working electrode are followed at open circuit. The principle was mentioned in a two-line statement by Barker who considered solely application to electrode kinetics. The method was rediscovered in this Laboratory in connection with a theoretical study of adsorption kinetics at an ideal polarized electrode . The expression "coulostatic method" was coined in thi s paper. Application of the method to analytical chemistry was soon announced and application to electrode kinetics was immediately developed. Independently, Reinmuth and coworkers and Gerischer also developed the study of fast electrode processes by this method.

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Diethylenetriaminepentaacetic acid (DTPA) has five carboxylic acid radicals and three nitrogen atoms as functional groups for formation of metal chelate compounds and forms chelate compounds with many metals. It was found by Schwarzenbachet al. and Chaberek that the values of formation constants of metal-DTPA complexes were larger than those of EDTA and CyDTA complexes. It was observed also with potentiometric titration by Chaberek and with amperometric titration by the authors' that the rare earth metal ions formed 1:1 chelate compounds with DTPA and their formation constants were determined. In this paper, pelarographic studies on the europium-DTPA complex are presented and the forrration constant of europium(II)- DTPA complex was determined.

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