酸素の微量分析

Abstract

Two modifications for the microdetermination of oxygen were proposed. Oxygen in the sample was converted to carbon mono oxide by the usual method, i.e. the pyrolysed products of the sample was passed through a layer of charcoal heated at 1100±5°. 1) Carbon monooxide was then oxidized with anhydroiodic acid (Hl3O8) and the amount of iodine liberated was determined gravimetrically, after it was caught by a silver net roll which was heated at 450_??_500°. The procedure is much simpler than that of UNTERZAUCHER's, yet the conversion factor is as profitable as that of his, i.e. 1mg iodine corresponds to 0.3152mg of oxygen, and the results of determinations were. satisfactory. 2) It was found that the samples which contained sulfur could be analysed satisfactory when the gas bubbled through water prior to contact with anhydroiodic acid. Hence a water bubbler was equipped between the ascalite scraper and anhydroiodic acid. It was supposed that the moisture might prevent the reaction between anhydroiodic acid and CS2 or COS. Note. a) The oxydation furnace and the anhydroiodic acid furnace must be placed 1 cm apart to prevent the overheating of anhydroiodic acid. b) Ascalite scraper must be renewed within a month, otherwise a larger oxygen value would result. c) Anhydroiodic acid is pre-pared in the following way: Dissolve iodinepentaoxde (I2O5) in a little amount of water and filter the solution while it is hot. To the syrup, at room temperature, be added concd. HNO3, to give a final concentration of 68 vol/vol%, and mixed homogeneously. Heat the solution at 100°. Crystals of anhy lroiodic acid would appear gradually. About 80% of the reagent would be recovered in the first crop. The reagent is not hygroscopic and does not react with hydrogen.