Sulphide, polarographic determination

During the anodic polarization of a dropping mercury electrode the chloride, bromide, iodide, cyanide, thiocyanide and sulphide ions form slightly soluble salts or stable complexes with mercury. In the presence of these substances so-called anodic oxidation waves appear on polaro-graphic curves. The polarographic determination of chloride has received most attention. In many cases the dilution of the sample with 0.1 N H2SO4 is satisfactory and the solution can be polarographed directly [3]. 

Polarographic determination of sulphite (including sulphide and thiosulphate)... 

If sulphide also has to be determined, first perform the analysis described under A). Then add 2 ml acetic acid to the solution, mix for 3 min. with nitrogen, and polarograph again. 

Procedure. Boil the fibre in 30 per cent sulphuric acid and trap the carbon disulphide set free in a U-tube (Fig. 40) filled with a 1 per cent ethanolic solution of diethylamine. Trap the hydrogen sulphide in a tube containing cadmium acetate solution, incorporated between the sulphuric acid and sample and the trapping U-tube. Determine the diethyldithiocarbamate formed polarographically, using the anodic wave of the mercury salt formation, as in the determination of carbon disulphide given in Chapter VI. 

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