Determination of chloride by displacement of hydrogen cyanide from mercury(II) cyanide.

A method, based on the passivity of mercury(II) cyanide in dilute sulphuric acid and its reaction with hydrochloric acid to produce hydrogen cyanide, has been developed for the determination of small amounts of chloride. Hydrogen cyanide, distilled from a mercury(II) cyanide-halide-dilute sulphuric acid system is found by iodometric measurement to be directly proportional to the amount of chloride or bromide and of hydrogen ion in acids such as sulphuric acid. A linear correlation also holds for iodide but the stoichiometry is different, the titration values being about three times larger than expected. By conversion of the cyanide into a dye by means of the pyridine-pyrazolone reagent, 0.014-0.43 mug ml chloride concentrations have been determined. The method is also applicable to bromide and sulphuric acid in small amounts but not to fluoride and iodide. Results are reproducible to within +/-2%.

Artifacts of the decalin-molecular sieve system in the analysis of mineral waxes.

Analysis of commercial paraffin waxes by use of molecular sieves and decalin has been shown to give misleading results because of the formation of additional compounds. The source and the nature of these compounds have been investigated and it has been found that they are polymers of partially dehydrogenated decalin. Care should be taken when using this solvent in such analyses.

Micro and semi-micro determination of organic nitrogen by use of potassium bromate.

After Kjeldahl digestion of an organic compound, nitrogen is determined by oxidation of the resultant ammonium sulphate with hypobromite produced in situ by the addition of an excess of potassium bromate and bromide in a special flask. The unreacted potassium bromate is determined iodometrically.