Using Indicators as Impurities to Monitor the Washing Process in the Organic Chemistry Laboratory

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Laboratory experiments provide training to students in experimental techniques and strengthen the understanding of the theory. Herein, a new introductory experiment for organic chemistry laboratory courses is described where students are trained in washing an unknown neutral organic compound using liquid/liquid extraction, isolating it via distillation, and identifying it using its boiling point. The use of indicators as impurities allowed for a fun visualization of the impurities appearing suddenly and students being able to see them disappear through the washing procedure. The success of the experiment was evaluated via in-lab observations, analysis of postlab reports/worksheets, and a postlab survey that included a test question. All of the students were able to wash their compounds to the point where no color from the indicators remained in the aqueous phases. Furthermore, 93% of the students were able correctly identify their unknown compound after distillation based on its boiling point, and 84% of the students explained what is happening chemically in the liquid/liquid extraction process to receive 75-100% of the points allocated for that explanation. A postlab worksheet with two general questions about how to separate organic compounds from one another using extraction, one of which was an extraction flowchart, was found to be better at helping students identify what solvent to use to wash an organic base from a neutral organic compound in the postlab survey. This shows the importance of designing well how the students work through the experiment and the experimental topic after the laboratory experiment.

Original languageEnglish
Pages (from-to)4796-4802
Number of pages7
JournalJournal of Chemical Education
Issue number12
Early online date22 Nov 2023
Publication statusPublished - 12 Dec 2023

Bibliographical note

Publisher Copyright:
© 2023 American Chemical Society and Division of Chemical Education, Inc.

Other keywords

  • Acids/Bases
  • Analogies/Transfer
  • Hands-On Learning/Manipulatives
  • Laboratory Instruction
  • Organic Chemistry
  • Second-Year Undergraduate
  • Separation Science


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