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.



Chemistry In Pictures

Chemistry in Pictures: Vapor diffusion

by Craig Bettenhausen
February 18, 2020

A vapor diffusion crystalization.
Credit: Tiffany Poynder

Tiffany Poynder had a nice surprise waiting for her in lab one recent Monday morning—crystals! Getting good crystals is always satisfying, and suggests that the compound in the vial is pure. But they’re crucial for Poynder, whose research is on perflourinated molecules that are difficult to isolate and characterize. Having nicely formed crystals to work with enabled her to use X-ray crystallography to identify what she had.

The crystallization setup shown in the photo is a classic called vapor diffusion. The molecule of interest is dissolved in a solvent or solvent mixture in the inner vial, which is left open. Then a different solvent, one that doesn’t dissolve the molecule well, goes around it in the outer vial, which is then capped tightly. Vapors of the outer solvent slowly mix in with the inner solvent (and vice versa), making the solvent in the inner vial less and less hospitable. Eventually the molecule can’t stay in solution, so it (hopefully) comes out as crystals.

Credit: Tiffany Poynder, @tiffany_poynder. Read more from this research: (Chem.–Eur. J. 2019, DOI: 10.1002/chem.201806110)

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

Related C&EN Content:

Chemistry in Pictures: Midair crystallization

Busting a myth about mechanochemical crystallization

Crystallization: Stunning Structures Spring From Humble Table Salt.


This article has been sent to the following recipient:

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