Simple multipurpose apparatus for solubility measurement of solid solutes in liquids

• Simple apparatus for solubility measurement of solid solutes in liquids is designed.
• Proposed apparatus is comparatively inexpensive and easy to assemble.
• Apparatus enables solubility measurements with small amount of solute.
• Apparatus is useful for crystallization, copigmentation and extraction experiments.

Solubility is one of the most basic chemical phenomena. It has a key role in understanding of major unit operations such as crystallization, solid–liquid extraction, and dissolution. In addition, solubility data is crucial for design, development, and operation of these processes. Therefore, solubility measurement of solid solutes in different solvents or solvent mixtures as a function of temperature can be of great significance to the university students and researchers. In this article, comparatively inexpensive apparatus for solubility measurement of solid solutes in pure or mixture of solvents, which can be easily assembled by using readily available equipment in the laboratory, is demonstrated. The proposed apparatus uses classical isothermal technique for measurement of solubility. Solubility of the naturally occurring antimalarial drug artemisinin was measured in n-hexane-ethyl acetate mixtures of varying composition at different temperatures to demonstrate the suitability and reliability of the proposed solubility measurement apparatus.The proposed apparatus has been used to conduct laboratory exercises in the course “Industrial Separation Technology” offered to undergraduate students of chemical engineering program at University of Southern Denmark. The exercises included solubility measurement and cooling crystallization of salicylic acid from five different organic solvents and extraction of artemisinin from the leaves of the plant Artemisia annua by using different solvents. Performance of the apparatus during laboratory exercises was evaluated through the survey among students. The results showed the general positive feedback from students and revealed enhanced interest among students to understand the exercises through the simple design of the apparatus.