| 摘要 |
PURPOSE:To take a measurement with accuracy enough to control reducing liquid by adding alkali to titrated liquid so as to keep the pH value of the liquid for alkalinity, even at the end point of titration. CONSTITUTION:The prescribed amount of sample is taken from a water solution as a measurement object, and an iodine solution is used as titrating liquid in the presence of alkali enough to keep the pH value of titrated liquid for alkalinity from the beginning of a titrating operation to the end thereof, thereby measuring a potential difference for oxidation reduction. In this case, a reducer for measurement is a boron hydroxide (for example, boron hydroxide sodium or derivative thereof) or hydrazine or sulfuric acid hydroxyl ammonium, or the derivative thereof. In order to keep the alkalinity of the titrated liquid, the pH value thereof is preferably kept between 11 and 13. For this purpose, alkaline metal hydroxide (for example, sodium hydroxide) is preferably added to the titrated liquid. A titration end point is preferably taken at the potential where an oxidation reduction potential difference is between +200mV and +350mV for a reference electrode. Concentration is calculated from a titrated amount at the end point. |
