"On the Solubility of Citric Acid in Propylene Glycol"

The solubility of citric acid in propylene glycol must be carefully observed in the changes of physical properties and environment. Citric acid is acidic, while propylene glycol is an organic solvent. The two are soluble, and its reason lies in the attractive force and repulsion between molecules.

Look at the structure of the molecule, citric acid has carboxyl and other functional groups, and propylene glycol contains hydroxyl groups. Hydroxyl and carboxyl groups can form hydrogen bonds, which are soluble groups. When the two are mixed, the molecules interact. If the ambient temperature and pressure are suitable, hydrogen bonds are born and the phase dissolves gradually.

At room temperature, citric acid gradually dissolves in propylene glycol, and the solution is clarified. However, when the temperature is raised, the molecular thermal motion plays a role, the hydrogen bond may break, and the solubility also changes. And the ratio of solvent to solute is also related to the degree of dissolution. If there is more propylene glycol and less citric acid, it is easy to dissolve; otherwise, it may be saturated.

The purity of the solvent also has a great impact. Pure propylene glycol, unlike those containing impurities, has different solubility to citric acid. Impurities or intermolecular forces interfere, making the solubility different.

To obtain accurate solubility, rigorous experiments are required, temperature control, mass measurement, and data are used to clarify the change. In this way, we can know the solubility of citric acid in propylene glycol, which provides evidence for various uses, such as chemical preparation, pharmaceutical preparation, etc.