Determination of autoprotolysis constants of ketones using hydrogen-palladium generator electrode.

A coulometric-potentiometric method for the determination of autoprotolysis constants of acetone and methyl ethyl ketone, is described. The method is based on the titration of a strong base, i.e., tetrabutylammonium hydroxide with protons obtained by anodic oxidation of hydrogen at an H(2)/pd electrode in the presence of tetrabutylammonium perchlorate as the supporting electrolyte. The titration was carried out in a galvanic cell with glass and calomel electrodes, at 25 degrees . The pK(s) value obtained for acetone and methyl ethyl ketone were 25.82 +/- 0.05 and 26.92 +/- 0.07, respectively.

The application of deuterium-palladium electrodes in the coulometric-potentiometric determination of bases in ketone media.

The application of deuterium-palladium electrodes as generator, indicator and reference electrodes for the determination of organic bases in acetone and methyl ethyl ketone has been investigated. Deuterium dissolved in palladium is oxidized at a potential that is close to the oxidation potential of hydrogen in palladium and more negative than the oxidation potentials of the bases titrated, indicator, and the solvents used. The anodic oxidation of deuterium dissolved in palladium proceeds with 100% current efficiency in the solvents investigated. The relative errors for the determination of 5 x 10(-4)M solutions of bases are less than 1%.

Coulometric generation of protons by oxidation of hydrogen dissolved in palladium, in non-aqueous media.

Coulometric generation of H(+) ions by the oxidation of hydrogen dissolved in palladium, in media such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, acetic anhydride and acetic acid-acetic anhydride mixture, for use in titration of bases, has been investigated. The hydrogen is oxidized at potentials which are much more negative than those of the bases and other components present in the solution. Titrations of numerous bases have established that the oxidation is quantitative and proceeds with 100% current efficiency.

Potentiometric determination of pK(A) of organic bases in acetone by the application of coulometry.

A coulometric-potentiometric method for the determination of pK(A) values of organic bases in anhydrous acetone is described. The bases were titrated with protons obtained by anodic oxidation of hydrogen dissolved in palladium, in the presence of sodium perchlorate as the supporting electrolyte. A pair of glass electrodes was used for measuring directly the difference between the half-neutralization potentials of the standard and the base being studied. The pK(A) values obtained were close to those reported in the literature. The effect of the supporting electrolyte concentration on the pK(A) values of some of the bases was also studied.

Coulometric generation of hydrogen ions by oxidation of mercury in anhydrous acetone.

The application of a mercury anode for the quantitative generation of H(+) ions in anhydrous acetone has been investigated. From the changes of anode potential with current density in 0.25M sodium perehlorate in anhydrous acetone it has been established that in this solvent mercury is oxidized at a potential which is much more negative than the oxidation potentials of the bases to be titrated, the indicator used and the solvent. Protons generated in this way have been used for titration of some organic bases, with either visual or potentiometric end-point detection. The oxidation of mercury in anhydrous acetone and the reaction of mercury ions with acetone have been found to proceed with 100% current efficiency.

Catalytic thermometric titrations in non-aqueous solvents by coulometrically generated titrant.

Catalytic thermometric titrations have been developed for tertiary amines and salts of organic acids in acetic and propionic anhydride with titrant coulometrically generated at a mercury and/or platinum anode, hydroquinone being added to the solution titrated if the platinum anode is used. The results obtained are compared with those obtained by coulometric titration with the end-point detected either photometrically or potentiometrically. On a élaboré des titrages thermométriques catalytiques pour les amines tertiaires et les sels d'acides organiques en anhydrides aétique et propionique avec l'agent de titrage engendré coulométriquement sur une anode de mercure et/ou platine, de l'hydroquinone étant ajoutée à la solution titrée si l'on emploie l'anode de platine. Les résultats obtenus sont comparés avec ceux obtenus par titrage coulométrique avec le point de fin de réaction détecté soit photométriquement soit potentioétriquement.

Coulometric titration of bases in acetic acid and acetonitrile media.

The working conditions and the results for coulometric titration of milligram amounts of some bases in 0.1M sodium perchlorate in a mixture of acetic acid and acetic anhydride (1:6), are given. Determinations were made both by coulometric back-titration or direct titration at the platinum anode. Back-titration was done in the catholyte, by coulometric titration of the excess of added perchloric acid. The titration end-point was detected photometrically with Crystal Violet as indicator. The direct titration of bases was done at the platinum anode, in the same electrolyte, to which hydroquinone was added as anode depolarizer and as the source of hydrogen ions, Malachite Green being used as indicator. Similarly, bases can be determined in acetonitrile if sodium perchlorate, hydroquinone and Malachite Green are added to the solvent. Errors are below 1 %, and the precision is satisfactory.

Determination of organic bases in non-aqueous solvents by catalytic thermometric titration.

Catalytic thermometric titrations have been developed for bases (brucine, diethylaniline, potassium acetate and triethylamine) in acetic acid by continuous and discontinuous addition of the standard solution and automatic temperature recording. The determination of weak bases, e.g., antipyrine, unsuccessful in acetic acid by catalytic thermometric titration, has been achieved by using nitromethane or acetic anhydride as solvent. Catalytic thermometric titrations were also performed by coulometric generation of hydrogen ions for the determination of micro amounts of weak bases in a mixture of acetic anhyride and acetic acid.

Determination of tertiary amines and salts of organic acids in acetic acid by catalytic thermometric titration.

A new method of determination of tertiary amines and salts of organic adds in acetic acid solution, to which about 2 % of water and 8% acetic anhydride are added, is described. After the equivalence point, the excess of perchloric acid catalyses the exothermic reaction of water with acetic anhydride. The end-point is determined from the graph of temperature against volume of added titrant. If a slightly soluble compound is produced during the titration, the precision of the new method is superior to that of the potentiometric method.