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在演示实验和学生实验中常可发现,酚酞滴入碱性溶液中变红,放置一段时间后,颜色会变浅。笔者对这一现象的原因进行了探究。一、红色变浅与CO_2、O_2无关笔者首先有两个猜测:①空气中的CO_2与碱性物质反应,溶液碱性减弱,使酚酞红色变浅;②酚酞被空气中的O,氧化,造成红色变浅。为了验证猜测是否正确,笔者进行了如下实验。
In demonstration experiments and student experiments can often be found, phenolphthalein drops into the alkaline solution turns red, after a period of time, the color will be lighter. The author explores the reasons for this phenomenon. First, the red light with CO_2, O_2 has nothing to do with the first two speculation: ① air in the reaction of alkaline and alkaline substances, alkaline solution weakened, lighter red phenolphthalein; ② phenolphthalein O in the air, oxidation, resulting Red lighter. In order to verify the speculation is correct, the author conducted the following experiment.