食盐中碘的溴邻苯三酚红褪色光度法测定

PHOTOMETRIC DETERMINATION OF IODINE IN TABLE SALT BY COLOR-FADING REACTION OF BROMOPYROGALLOL RED （BPR）

在硫酸介质中（PH=2．4），碘酸根能氧化溴邻苯三酚红使之褪色，且褪色的程度与碘酸根的存在量有关，从而建立了光度法测定碘的方法。有色溶液的最大吸收波长为510nm，碘的存在量在0—30ig／25ml范围内符合比耳定律，表观摩尔吸光系数ε：1．81×10^4L/mol·cm。方法简便、快速、选择性好，准确度高，用于测定食盐中微量碘时，结果满意。

In a dilute sulfuric acid medium（pH=2.4）, BPR is oxidized by 103, leading to the color-fading of the color reagent, or more explicitly causing a decrease of absorbance at 510nm, the wavelength of one of the two absorption peaks of BPR reagent. The magnitude of decrease of absorbance（AA） is proportional directly to the increase of concentration of IO3（expressed as Г） in the range 0 to 30i g per 25mL of solution. The apparent molar absorptivity（a） is 1.81×10^4L/mol·cm. This method is simple, rapid, accurate and precise, and has been successfully used in the determination of iodine in table salt.