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鉴别化肥的性质时,如果在农村中买不到石蕊试液。可用黑豆皮一部分,放在凉水中浸泡一小时左右,或煮过后水就成了黑紫色。这种水就能代替石蕊试液用,如将化肥少许溶于试管中,再倒上黑豆皮水,如试管中的化肥溶滤变为粉红色,就是酸性肥料,如果变成黑色就是碱性肥料,如不变色就是中性肥料。用这一方法让同学们普遍进行了实验,学生们一致的说:“这个方法真好,既捷便又易行不用化钱能办大事,适合农村公社使用……”。
Identify the nature of fertilizer, if you can not buy litmus liquid in rural areas. Black bean skin can be used in part, soak in cold water for about an hour, or boiled water became black purple. This water can replace litmus solution, such as a little fertilizer dissolved in the test tube, and then poured on the black bean skin water, such as test tube fertilizer dissolved into pink, is acidic fertilizer, if it is black is the base Fertilizer, if not discolored is a neutral fertilizer. In this way, students carried out experiments universally. The students unanimously said: “This method is very good. It is both convenient and feasible to do great things without money and is suitable for use by rural communes.”