A Critical Study on the Methods of Water Analysis. (VIII)

[摘要] I. The method of determination of dissolved oxygen, proposed by Winkler, is based on the determination of manganic oxide, produced from manganous oxide by the oxidative action of dissolved oxygen. In his method, iodometry is adopted. The writer adopts permanganometry: Dissolved oxygen is fixed by Mn++ and alkali, the manganic oxide is reduced with sulphuric acid and excess of oxalic acid, and the remaining oxalic acid is determined with permangante. In this case no heat is necessary, as the acidified solution contains excess of Mnt++(Skrabal). The normal solutions of oxalic acid and permangante are commonly used for the dissolved organic matter. Corrections for reducing constituents of water, such as organic matter, Fe++ and NO2- can be made.II. To obtain the degree of saturation of dissolved oxygen, vappur pressure correction is to be applied for the solubility data such as those of Fox or of Jacobsen. When the barometer stands at 760mm, Whipple and Whipple's table can be used, but in general we need the value of (p-e)/P or 1-(e/P) where P and e denote barometric pressure and vapour pressure. A table of this correction to the third decimals, over the range of 0°-30°C and 600-780mm is given.

[学科分类] 大气科学