Balbir Chand Verma

Determination of thiuram disulphides and analysis of thiuram disulphide-dithiocarbamate mixtures.

Potassium trithiocarbonate is used as reluctant for the titrimetric determination of thiuram disulphides in dimethylformamide-water media. The method is based on reductive cleavage of the disulphide linkage to yield the corresponding dithiocarbamates. In visual titrations, the end-point is marked by appearance of a yellow colour with the first drop of reagent added in excess. The method is simple, accurate, reliable and of wide applicability. It has been successfully extended to the analysis, in the same sample solution, of thiuram disulphide-dithiocarbamate mixtures.

Spectral and magnetic studies on normal cobalt(II) planar and cobalt(III) octahedral, spin-crossover cobalt(III) octahedral and planar-tetrahedral cobalt(II) carbodithioates

Abstract Five cobalt(II) complexes, a normal complex Co(4-PPipzcdt) 2 (4-PPipzcdt = 4-phenylpiperazine-1-carbodithioate), and four zwitterionic complexes, Co(4-PPipzcdtH) 2 X 2 and Co(4-MPipzcdtH) 2 X 2 (X = Cl, Br; 4-PPipzcdtH = 4-phenylpiperazine-1-carbodithioic acid, 4-MPipzcdtH = 4-methylpiperazine-1-carbodithioic acid), have been synthesized. Normal cobalt(III) complexes of the type Co(4-MPipzcdt) 3 and Co 2 {2-MPipz(cdt) 2 } 3 (2-MPipz(cdt) 2 = 2-methylpiperazine-1,4-dicarbodithioate) and two zwitterionic cobalt(III) complexes of the type Co(4-MPipzcdtH) 3 X 3 (X = Cl, Br) have also been obtained. In addition to the room temperature IR and electronic spectra and magnetic susceptibility studies, all the complexes, except the normal Co(4-MPipzcdt) 3 and Co(4-PPipzcdt) 2 and zwitterionic Co(4-MPipzcdtH) 3 Cl 3 , have been investigated by variable-temperature magnetic susceptibility measurements. The results of the variable-temperature magnetic susceptibility studies suggest that two cobalt(II) carbodithioates exhibit a square planar-tetrahedral equilibrium, while two cobalt(III) octahedral carbodithioates show a spin-crossover phenomenon.

A new colorimetric method for the determination of carbon disulphide and its application to the analysis of some dithiocarbamate fungicides.

A new and convenient colorimetric method for determination of carbon disulphide, based on its transformation into bright yellow potassium benzyl trithiocarbonate through reaction with benzyl mercaptan and potassium hydroxide in tert.-butyl alcohol, has been successfully applied to determination of some dithiocarbamate fungicides in their formulations. The method possesses a distinct advantage in that it is free from all sources of errors/problems which are associated with the xanthate method for the analysis of these materials. The proposed method is precise and accurate and hence recommended for routine analysis of technical formulations containing dithiocarbamate fungicides.

Non-aqueous redox determination of ascorbic acid with copper (II)

Hydrated copper (II) perchlorate (in acetonitrile) has been used for the direct visual and potentiometric determination of ascorbic acid in acetic acid-acetonitrile media. Diphenylamine and diphenylbenzidine are suitable indicators. A bright platinum wire is used as indicator electrode and a modified calomel or an antimony electrode as reference electrode for the potentiometric titration. Ascorbic acid is oxidized to dehydroascorbic acid. The proposed method is simple, accurate and reliable. The reverse titration also works well.

Analytical applications of copper(II) and copper(I) in acetonitrile: potentiometric and spectrophotometric determination of dithiocarbamates

The use of copper(II) perchlorate and tetra-acetonitrilocopper(I) perchlorate (in acetonitrile) for the potentiometric and spectrophotometric determination of dithiocarbamates in acetonitrile medium is described. The proposed methods are simple, accurate and reliable and show promise of wide applicability. They are recommended for routine determination of dithiocarbamates. Their advantages over the carbon disulphide evolution method, commonly employed for the determination of these compounds, are discussed.

Analytical applications of the amine-carbon disulphide reaction in acetonitrile.

The ease with which carbon disulphide transforms primary and secondary amines in acetonitrile medium into the corresponding monoalkylammonium monoalkyldithiocarbamates and dialkylammonium dialkyldithiocarbamates respectively and the simplicity and reliability of potentiometric and spectrophotometric determination of dithiocarbamates with copper(I) perchlorate in the same medium, provide simple, accurate and reliable methods for the determination of primary and secondary amines and of organic isothiocyanates.

Alkalimetric determination of mercaptans through trithiocarbonic acid formation.

A simple and rapid alkalimetric method for the determination of mercaptans through trithiocarbonic acid formation is described. The mercaptans are titrated in tert.-butanol in the presence of carbon disulphide with standard aqueous sodium hydroxide, with phenolphthalein as indicator. The -SH group is smoothly, rapidly and quantitatively transformed into the group under the specified conditions. The method has been extended to the analysis of mercaptan-carboxylic acid and mercaptan-trithiocarbonate mixtures.

Determination of mercaptopyrimidines with copper(II) in acetonitrile.

A non-aqueous oxidimetric method is described for the determination of mercaptopyrimidines with copper(II) perchlorate in acetonitrile, diphenylamine being used as indicator. A bright platinum wire is used as indicator electrode and a modified calomel or an antimony electrode as reference for potentiometric titrations. The method, based on the oxidation of the mercapto group to the disulphide, is simple, accurate and reliable.

Redox reactions in nonaqueous media determination of amines via dithiocarbamate formation and iodine monobromide titrations

Abstract A simple and accurate nonaqueous oxidimetric method of wide applicability has been developed for the determination of primary and secondary amines after their quantitative conversion with carbon disulphide in acetonitrile to the alkylammonium alkyldithiocarbamates, which are titrated with iodine monobromide solution also in acetonitrile at room temperature. The endpoint is detected visually by the yellow tint imparted to the solution by the first drop of oxidant solution in excess; and potentiometrically by using a bright platinum wire indicator electrode, and antimony or modified calomel reference electrode. The method is simple, rapid, accurate, and widely applicable.

Redox reactions in non-aqueous media: Determination of organic isothiocyanates alone, in formulations and in important mixtures

A simple potentiometric method for the determination of organoisothiocyanates is described. The isothiocyanate is treated in acetonitrile medium with an excess of primary amine to convert it into a substituted thiourea and the surplus amine is converted into a dithiocarbamate by addition of carbon disulphide. The solution is then titrated with a copper(II) solution in acetonitrile. The three-step titration curve enables the results to be calculated on the bash of the dithiocarbamate and/or thiourea formed. The method has been successfully applied to the analysis of a commercial insecticide formulation based on isothiocyanate and important mixtures containing isothiocyanates.