利用投影片達到減量的實驗設計──應用酸鹼指示劑測定鹽類溶劑之pH值

A Spot Test Carried Out on a Transparency to Minimize Chemicals Consumption ── pH Measurements of Salt Solutions by Acid-Base Indicators

余瑞琳(Jui-Lin She) ； 張博文(Bo-Wen Chang) ； 鄭淑芬(Soo-Fin Cheng)

《化學》 53卷2期 (1995/06) Pp. 185-188

https://doi.org/10.6623/chem.1995016

摘要

由於修習普通化學實驗的學生人數龐大，實驗藥品的用量、準備工作及廢污產量均極大，因此，本研究中設計一種在投影片上進行的點滴實驗。將七種經稀釋的酸鹼指示劑分別滴入pH值為1-13之緩衝溶液中，以觀察指示劑顏色變化的pH範圍；進而利用指示劑顏色變化，測定各種鹽類水溶液的pH值，以計算此鹽類的陽離子或陰離子在水中的水解度。實驗結果顯示，此實驗顏色變化明顯、易於觀察；以點滴實驗所測的指示劑顏色變色範圍與理論相符，鹽類水溶液滴加指示劑後，其顏色與已知pH值緩衝直接對比，可與正確決定溶液的pH值。每次實驗，試劑用量很少，每組學生操作一次實驗，每一試劑至多使用1 mL，藥品的用量及實驗廢液產量均被少許多；以塑膠滴管成裝試劑，若學生遵守使用規定，藥品被污染的機率不大；而投影片極易清洗，其與塑膠滴管均可一再重複使用，因此極適合應用於學生實驗。

關鍵字

普化實驗 ； 減污減廢 ； 酸鹼指示劑 ； 鹽類水解

並列摘要

In order to reduce the amount of chemical reagents used in General Chemistry Laboratory, an experiment entitled ＂pH measurements of salt solutions by acid-base indicators＂ was designed and carried out by spot test on a transparency. The color change behaviors of seven common acid-base indicators in standard pH buffer solutions (pH 1-13) were recorded. Then, the pH values of several salt solutions were determined and the degree of hydrolysis of these sail species could be calculated accordingly, all by the spot test on a transparency. The color changes of indicators were clearly viewed against a sheet of white paper. The results showed that the pH transition regions of the indicators as well as the pH values of the salt solutions were in 11 close range to those reported in the literatures. The amount s of chemicals consumed and waste produced in this experiment were greatly reduced, in comparison with those in traditional experiments. Furthermore, the transparencies and plastic pipets used could be recovered and re used after each laboratory work. This experiment is very suitable for General Chemistry laboratory.

並列關鍵字

General chemistry laboratory ； Reduction of chemical waste ； Acid-base indicaotrs ； pH measurements of salt solutions