Ionic polymerisation as a means of end-point indication in non-aqueous thermometric titrimetry. Part VII. The determination of O-alkyl dithiocarbonates and metal iodides

Abstract

Lead, nickel, potassium, sodium and zinc O-alkyl dithiocarbonates have been determined in amounts down to 0·002 mequiv by catalytic thermometric iodimetric titration of their solutions in dimethylformamide, acrylonitrile or chloroform. The end-points of the titrations correspond to the formation of the metal polyiodides, and the method is more sensitive than conventional aqueous iodimetry for the determination of potassium and sodium alkyl dithiocarbonates, in which a monoiodide is the final product. The results show precisions ranging from 0·20 to 1·15 per cent. when a 0·05 M titrant is used.The mechanisms of the titration reactions have been confirmed by titrating solutions of the metal iodides in dimethylformamide by the iodimetric method, and this procedure can be used for the determination of nickel, potassium, sodium and zinc iodides in non-aqueous solution.Impurities such as sulphides, sulphites, thiosulphates, sulphates, carbonates and trithiocarbonates can be separated from technical-grade dithiocarbonates before analysis by using the appropriate solvent for the sample and centrifuging the solution.Sodium and potassium alkyl dithiocarbonates in aqueous solution have been determined as the corresponding nickel salts by a modification of an established solvent-extraction method.