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用25型酸度计测定洗衣粉的pH值已有多年历史,目前各洗衣粉厂仍在采用这种仪器,在使用过程中,必然涉及玻璃电极的选用,蒸馏水的纯度和操作方法等事项。据了解,有些检验工作者对这些事项还注意得不够,致使测定结果存在误差。现把我所作的试验和见解叙述如下,供读者参考。一、试验方法精确称取0．5克样品于50毫升烧杯中,加入煮沸后并冷却的蒸馏水50毫升,使样品充分溶解,至20℃待测。
Determining the pH value of washing powder with 25 type acidity meter has been going on for many years. At present, all kinds of washing powder factory are still using this kind of instrument. In the process of using, the selection of glass electrode, the purity of distilled water and the method of operation are bound to be involved. It is understood that some inspectors also pay insufficient attention to these issues, resulting in the measurement error. I now make the test and insights described below, for readers reference. First, the test method Accurately weigh 0.5 grams of sample in a 50 ml beaker, add boiled and cooled 50 ml of distilled water, the sample was fully dissolved, to 20 ℃ to be measured.