紫外分光光度法测水总硬度显色条件的选择

摘要

在利用紫外分光光度法对水样硬度进行测定的过程中,针对铬黑T的显色时间、显色条件及吸收波长的选择进行了一系列的实验研究.实验结果表明,在pH 11.60的缓冲溶液中,Ca2+、Mg2+与铬黑T形成紫色络合物,于531 nm均有最大吸收,且曲线具有加和性.钙、镁的摩尔吸收系数分别为3.40×104和5.63×104 L/(mol·cm).为紫外分光光度法测水样中Ca2+、Mg2+混合离子的总含量提供了一种有效的方法,同时得到了一些有益的结论.用该方法和滴定分析法分别对同一水样的硬度进行检测,结果相差不大.%In the determination of the hardness of tap water sample using ultraviolet spectrometry, the coloration time, color condition and absorption wavelength were studied according to the color reagent of EBT. The results indicate that in a buffer solution of pH 11. 60, Ca2+ and Mg2+ reacted with the above mentioned reagent to form violet complexes with the same absorption maxima of 531nm. The molar absorptivities found are 3.40×104 and 5.63×104 L/(mol·cm) for calcium complex and magnesium complex respectively. This paper propose a kind of effective method for the ultraviolet spectrometry to measure the total content of the Ca2+ and Mg2+ in water sample. The hardness of water samples detected by using this method and that obtained by using titrimetric analysis has little discrepancy.