n.酚酞（一种测试碱性的试剂，可作刺激性泻剂）

Phenolphthalein is commonly used as an indicator in acid-base titrations because it changes color in the presence of an acid or base.
苯酚酞常用于酸碱滴定中，因为它在酸或碱存在时会改变颜色。
The solution was tested with phenolphthalein, which turned pink when it encountered an alkaline substance.
用苯酚酞测试了溶液，遇到碱性物质时它会变粉红色。
In this experiment, we added a few drops of phenolphthalein to the sodium hydroxide solution to observe the reaction.
在这个实验中，我们向氢氧化钠溶液中加入了几滴苯酚酞以观察反应。
The chemist dissolved a small amount of phenolphthalein in water and then added hydrochloric acid, observing the color change.
化学家将少量苯酚酞溶解于水中，然后加入盐酸，观察颜色的变化。
A student titrated a vinegar sample with sodium hydroxide, using phenolphthalein to determine the exact concentration of acid.
学生用苯酚酞对醋酸样品进行滴定，以确定酸的确切浓度。
The indicator phenolphthalein is colorless in neutral solutions but turns pink in basic ones, making it useful for identifying pH shifts.
指示剂苯酚酞在中性溶液中是无色的，但在碱性溶液中变为粉红色，有助于识别pH变化。
The experiment involved adding phenolphthalein to a known concentration of acetic acid to detect its presence.
实验中，往已知浓度的醋酸中加入苯酚酞来检测其存在。
The chemist carefully mixed the reactants, ensuring the addition of phenolphthalein only after the base had been thoroughly mixed.
化学家仔细混合反应物，在充分混合碱后才添加苯酚酞。
The teacher demonstrated the reaction between an acid and base by adding phenolphthalein to the mixture, which instantly changed color.
老师通过向混合物中添加苯酚酞演示了酸碱反应，颜色立刻发生了变化。
In a school science project, students used phenolphthalein to study the difference in pH levels between lemon juice and baking soda.
在学校的科学项目中，学生们用苯酚酞来研究柠檬汁和小苏打之间的pH值差异。