Swatantar Kumar

Non-aqueous cerimetric determination of thioureas

Ammonium hexanitratocerate (in acetonitrile) solution has been used as an oxidimetric reagent for the visual and potentiometric determination of thiourea and its alkyl derivatives in acetonitrile medium. The thioureas are oxidized to their corresponding disulphides. The method is simple, accurate, reliable and widely applicable.

Determination of organoisothiocyanates alone and in mixtures with organoisocyanates or thioureas

An iodatometric method for the determination of organoisothiocyanates is described. The isothiocyanates are quantitatively converted with n-butyl-amine in dimethylformamide medium into the corresponding symmetrical NN-disubstituted thioureas, which are titrated visually or potentiometrically in acidic medium with potassium iodate solution. Methods have also been developed for the analysis of isothiocyanate-isocyanate and isothiocyanate-thiourea mixtures on the same sample solution. A known excess of the standard n-butylamine solution added to the mixture in dimethyl-formamide converts the isothiocyanate and isocyanate into the corresponding disubstituted thiourea and urea, respectively. Acidimetric titration of the excess of amine, and iodatometric titration of the thiourea present and formed, enable the particular mixture to be analysed for both constituents. The end-points can be detected both visually and potentiometrically. The methods described are simple, accurate, reliable and widely applicable.

Determination of organotrithiocarbonates with iodine and iodine halides in non-aqueous media

The determination of organotrithiocarbonates with iodine and iodine halides in acetonitrile medium by visual and potentiometric method is described. The visual end-point is indicated by a sharp colour change from straw yellow to deep yellow caused by the first drop of oxidant solution in excess. Potentiometric titrations are performed with antimony or modified calomel reference electrodes and a bright platinum wire as an indicator electrode. The proposed method is simple, requires very little time because of the rapidity of the reaction, and the minimum of apparatus.

Indicators in non-aqueous cerimetric titrations of thioureas and xanthates.

The use of some chemical indicators in the non-aqueous cerimetric determination of thioureas and xanthates in acetonitrile medium is described.

Non-aqueous redox titrations with iodine and iodine halides. Determination of xanthates and dithiocarbamates

SummaryIodine and iodine halides (monobromide, monochloride and trichloride) solutions in acetonitrile have been used as oxidimetric reagents for the visual and potentiometric determination of alkali metal salts of xanthic and dithiocarbamic acids also dissolved in acetonitrile. The methods are simple, accurate, rapid and widely applicable.ZusammenfassungJod und dessen Halogenverbindungen (Monobromid, Monochlorid und Trichlorid) in Acetonitril gelöst wurden als oxydimetrische Reagenzien zur visuellen und potentiometrischen Titration von Alkali-Xanthogenaten und-dithiocarbamidaten in dem genannten Lösungsmittel verwendet. Das Verfahren ist einfach, genau und vielseitig anwendbar.

Amperometric determination of organic isothiocyanates.

An amperometric titration method is described for the determination of 1-5 mg of organic isothiocyanates, based on their quantitative reaction with n-butylamine in dimethylfonnamide to form N,N-disubstituted thioureas which are then titrated amperometrically in aqueous ammonia-ammonium nitrate buffer with silver nitrate (dropping mercury electrode at -0.56V). The end-point corresponds to a silver:thiourea ratio of 2:1, with precipitation of silver sulphide. The method is simple, accurate, widely applicable, and gives reproducible results.

Oxidimetric determination of thiourea-xanthate and thiourea3-dithiocarbamate mixtures.

A convenient and accurate method has been developed for the analysis of thiourea-xanthate and thiourea-dithiocarbamate mixtures by oxidimetric titration of the mixture with iodine monobromide first in acetonitrile medium and then in acidic aqueous acetonitrile medium. The end-points can be detected both visually and potentiometrically. The methods are rapid and have wide applications.

Determination of primary and secondary amines alone and in mixtures with tertiary amines

An iodatometric method has been developed for the determination of primary and secondary amines that is based on their quantitative reaction with phenyl isothiocyanate in dimethylformamide to form substituted thioureas. These are titrated with potassium iodate in an acidic medium at room temperature. The end-point is detected visually by the yellow colour imparted to the solution by the first drop of the iodate solution in excess, and potentiometrically by using a bright platinum-wire indicator electrode and a saturated calomel reference electrode. Methods have also been developed for the determination of primary (or secondary) amines and tertiary amines in the presence of each other. An excess of phenyl isothiocyanate, added to the mixture in solution in dimethylformamide, converts the primary (or secondary) amines into the corresponding di-(or tri-) substituted thioureas, whereas the tertiary amines are left unreacted. The conductimetric titration of tertiary amines with trichloroacetic acid, followed by the iodatometric titration of thioureas formed, enables the mixture to be analysed for both components. The methods described are simple, accurate and reliable.