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.