Abstract
The so-called iodometry has been used as an International Standard Method for the determination of hydrogen sulfide or sulfur dioxide in air but this method gives an extremely erroneous results if caution is not exercised in various points. For such reasons, air entirely devoid of hydrogen sulfide and sulfur dioxide was submitted to this method for examination. From the results thereby obtained, it has become clear that following points should be noted in using this method for a quantitative determination:
(1) Iodine is easily lost by vaporization, the amount of loss being extremely great, when air is bubbled or when the atmospheric temperature is high.
(2) In order to trap escaping iodine, a tube containing sodium thiosulfate must be attached by means of a ground-glass joint. Rubber tubing must never be used.
(3) The distilled water and starch reagent used must be those which have previously consumed iodine.
(4) The reaction itself can be used as such for quantitative determination.
(5) It is desirable te chill the iodine tube with ice to be maintained at around 0°C.
