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针对水质挥发性酚测定中常遇到的蒸馏液变黄,馏出液带色,试剂变质等异常问题,结合自己的工作经验提出了解决办法.1 蒸馏液变黄1.1 蒸馏过程中蒸馏液退色变黄常因甲基橙指示剂在加热的酸性溶液中被氧化物质(如余氯、溶解氧等)破坏分解而造成,应在蒸馏结束后,放冷再滴加几滴甲基橙指示剂液,水样即可恢复变红.故酸化时甲基橙指示剂应过量.1.2 蒸馏液退色变黄的另一原因是由于水样中的难溶性碱性盐类物质在加热后溶解度增大,继续中和过量的部分酸,使水样中的甲基橙指示剂变为黄色.遇此现象,只要向蒸馏瓶内补加适量的酸,水样可恢复变红.因此,在日常水质测定工作中,为了保证水样在蒸馏过程中始终呈酸性,使水样中的挥发酸能完全蒸馏出来,应在酸化时加酸稍过量为宜.
For the determination of water quality volatile phenol often encountered in the distillate yellowing, distillate color, reagent deterioration and other anomalies, combined with their own work experience proposed solutions.1 yellowing of the distillate distillation 1.1 Distillation discoloration Yellow often methyl orange indicator in the heated acidic solution is oxidized substances (such as residual chlorine, dissolved oxygen, etc.) damage caused by decomposition should be after the end of the distillation, let cool and then add a few drops of methyl orange indicator solution , Water samples can be restored to red, so the acid methyl orange indicator should be excessive .1.2 distillate fade yellow another reason is due to the water sample of insoluble alkaline salts in heating solubility increases, Continue to neutralize excess acid, so that the water sample of methyl orange indicator turns yellow In this case, as long as the distillation flask to add the right amount of acid, water samples can be restored to red, so in the daily water quality determination In the work, in order to ensure that the water sample is always acidic during the distillation process, the volatile acids in the water sample can be completely distilled off, and it is advisable to add a little acid during acidification.