Electrode chloranil reference

The number of unsaturated bonds can be determined by a titration with a standard solution of bromine dissolved in glacial acetic acid. The sample is also dissolved in glacial acetic acid to which sodium and ammonium acetate are added, so as to give a final concentration of 0-5 and OT M respectively. The cathodic current of bromine is measured with a short circuit system using a rotating platinum indicator, and a calomel or chloranil reference electrode at the potential of the reference electrode. Several unsaturated open chain compounds and terpenes have been titrated in this way.( ) Other modifications of this technique have been used to determine the amount of unsaturation in fats in methanolic solutions. The standard solution of bromine is prepared in methanol, saturated with sodium bromide, and the methylester of stearic acid is added to suppress the maxima. If the methanolic solution is acidified, OT M potassium bromate with OT M sodium bromide can be used instead of bromine. The bromine generated in homogeneous solution can be used to analyse xylenol and cresol fractions of coal-tars. Other phenolic compounds may be similarly determined. The method was used for the determination of small concentrations of styrene... 

The tetrachloroquinone (chloranil)/tetrachlorohydroquinone system has been used as a reference electrode in alcohols and acetic acid [222], often in the presence of an excess mineral acid. The half-cell consisted of a platinum electrode in a solution saturated with respect to both chloranil and the hydroquinone. The electrode is well poised, and at constant temperature and constant hydrogen ion activity the potential is stable. 

For electromotive force measurements there are many suitable electrodes, and only the most novel features can be summarised here. The glass electrode is generally usable in these solvents. It has been found that in solutions of hydrochloric acid in anhydrous acetic acid, the glass electrode is subject to acid errors of as much as 70 mV relative to the chloranil electrode, owing to the incorporation of chloride ions in the surface gel layer of the glass. ° Since ethylenediamine reacts with calomel but not with mercury (II) chloride, a suitable reference electrode for this solvent can be constructed of a mercury pool in contact with ethylenediamine saturated with respect to both HgClg and LiCl. °... 

Data based on tables in Ref. [2] and references therein values in eV obtained in acetonitrile, H20, or other polar solvents redox potentials are reported vs. standard calomel electrode calculation of AGeI performed with Eq. (13). Abbreviations CA = chloranil CN = 1-cyanonaphthalene bpy = 2,2 -bipyridine, MV2+ = methylviologen dicp = 1,3-diisocya-nopropane and TMB = N,N,iV, N -tetramethylbenzidine... 

---