A Colorful Solvent Extraction Demonstration for Teaching the Concept of “Like Dissolves Like”

Abstract

The concept of "like dissolves like" is explored using a solvent extraction demonstration appropriate for first-year chemistry students. Equal volumes of aqueous methyl red and blue copper(II) sulfate form a purple solution. 1-Pentanol is added and floats on top as a clear layer due to its lower density and low water solubility. Vigorous shaking for a few seconds causes the alcohol to mix with the other reagents and extract the methyl red. Upon standing, the alcohol layer reseparates as a red layer floating on top of the now blue layer of aqueous copper(II). The demonstration is easy to prepare and perform and has an impressive visual impact.

Azo dyes synthesis demonstrations for education purposes

“…These experiments can take students on a true research experience, including many aspects of real research -learning about the importance of protection of functional groups and use of alternative diazotation in isopropanol as compared to diazotation in water to provide a more reliable and higher-yield method of isolation of the azo product. As it has been demonstrated before in recent years, azo dyes are also useful for demonstrations of extraction and how it works in connection with acid-base extraction methods [2,3]. These acid-base dependent color-changing properties are also visible on ethyl 3-(2', 4'-dihydroxyphenylazo)benzoate, together with its different solubility, which is also demonstrated as one of possible ways of isolating this resulting azo dye in this paper.…”

Efficient and Simple Extraction Protocol for Triterpenic Acids from Apples

“…The use of different solubilities of extracted compounds has already been described in a number of experiments suitable for students and represents an important key learning objective for extraction processes. 20,23,24…”

“…Performing these steps helps the students to understand the properties of different solvents, their polarity, and their miscibility and their uses for extraction and purification. The use of different solubilities of extracted compounds has already been described in a number of experiments suitable for students and represents an important key learning objective for extraction processes. ,, …”

“…The remaining more polar compounds are removed by liquid–liquid extraction with water. In order to learn and train the liquid–liquid procedure, we recommend the school experiment published by McKnelly et al or Dobberpuhl et al , After evaporation of the organic phase, the dried extract is boiled for 10 min in cyclohexane to remove non-polar compounds (Step 3). In this degreasing step, lipids are removed.…”

A Novel Green Sample Pretreatment Method Column-Free Matrix Solid-Phase Dispersion Extraction: Application in a High-Performance Liquid Chromatography Experiment for Undergraduate Chemistry

“…2−4 HPLC needs to be combined with some sample pretreatment techniques to realize the separation and detection of actual samples. In undergraduate laboratory experiments, 5,6 traditional sample pretreatment methods are usually used, such as solvent extraction, 7,8 solvent reflux extraction 9,10 and ultrasonic-assisted extraction. 11, 12 These methods take a long time, use a large amount of organic solvents, and require a relatively cumbersome operation.…”