酚酞指示剂

酚酞指示剂遇无水醇钠醇溶液变色的探讨

Briefly on Colour Changing of Alcoholic Solution when Phenolphthalein Indicater Contacts with Anhydrous Sodium Alcoholate

样品以石油醚提取后，过滤，加入50%乙醇溶液，以酚酞为指示剂，用KOH标准溶液滴定至下层溶液呈微红色。

The procedure is as follows : Extract free fatty acids by petroleum ether , and add 50 % ethanol solution after filtration , then titrate with standard volumetric potassium hydroxide solution using phenolphthalein as indicator until the end-point indicated by a sharp change of color from neutral to pink .

通常测定酸值时，一般使用酚酞作为指示剂。

Conventionally , acid number is determined by use of phenolphthalein as indicator .

用经典的以酚酞作指示剂测定碳酸钠的方法，终点不稳定；

Using phenophthalein to make indicator to measure sodium carbonate , the end point is instable .

但是对于改性聚酯多元醇，用酚酞作为指示剂其终点难以判断，故采用电位滴定法测聚酯亚胺多元醇的酸值，同时使用各种酸碱指示剂用来指示滴定终点，结合两者得出一个最佳的指示剂。

But it is difficult for end point determination in modified polyester polyol system . Therefore potentiometric titration is used for determination of acid number of polyester imide , as well as pH indicators .

混合碱测定中第一计量点及第二计量点的判断，由于酚酞，甲基橙指示剂终点不敏锐，效果不佳。

Phenolphthalein and methyl orange as indicators for the determination of mixed base are insensitive to the titration point , and results in the errors of measurement .

甲基橙做指示剂的酸碱滴定实验操作的几点改进终点时颜色变化非常敏锐，是一种优于酚酞、甲基橙的指示剂。

At the end of the titration the colour changes sharply .

选择溴甲酚绿和酚酞一百里酚酞为指示剂。

Bromoc-resol Green and Phenolphthalein-Thymolphthalein were selected as indicators .