If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.


Physical Chemistry

Chemistry In Pictures

Chemistry in Pictures: Solid + solid = liquid?

by Craig Bettenhausen
March 2, 2021

Three vials contain, from left, large clear crystals, smaller cloudy crystals, and a clear liquid. All are colorless.
Credit: Submitted by Liane Meneses and Luísa Pereira/Project Des.Solve

Can a mix of solids form a liquid? In a “deep eutectic system” (DES), yes. In these cases—which includes some mixtures of sugars, amino acids, and organic acids—compounds that are typically solid at room temperature lower each other’s melting points when combined in some ratios. As a result, they melt. Starting at the left, this picture shows two natural compounds, menthol and lauric acid. Combined in a certain molar fraction as they were heated and stirred, the compounds formed the eutectic liquid in the flask on the right. After the liquid is formed, it remains stable at room temperature. This is also what happens with honey, a naturally occurring DES that is a viscous liquid resulting from the mixture of various sugars. Project Des.Solve, funded by the European Research Council, aims to extend knowledge of these systems, focusing on their characterization and boosting application to fields including extraction, biocatalysis, green chemistry, and biomedical science.

Submitted by Liane Meneses and Luísa Pereira/Project Des.Solve

Do science. Take pictures. Win money. Enter our photo contest here.

Click here to see more Chemistry in Pictures.


This article has been sent to the following recipient:

Chemistry matters. Join us to get the news you need.