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Physical Chemistry

Chemistry In Pictures

Chemistry in Pictures: Winter is coming

by Alexandra Taylor
April 16, 2019

A micrograph of a large, liquid water droplet in the center of an array of smaller, frozen droplets.
Credit: Rukmava Chatterjee

This array of water droplets illustrates how salt slows ice formation. The large condensed water droplet in the center contains a single crystal of sodium chloride. An array of smaller condensed water droplets surrounds it. Rukmava Chatterjee, a PhD candidate at the University of Illinois at Chicago, studies anti-icing systems. Chatterjee added a single sodium chloride crystal to a plate cooled to –15 °C. The air around the plate was room temperature and humid. As vapor from the air condensed on the plate, the central drop remained liquid for about 3 h, while the smaller drops froze after about 20 min. Chatterjee captured this image in grayscale at 100× magnification; he adjusted the hue and saturation to give it a violet tint. Deicing is critical for safe winter driving, but rock salt can have detrimental effects on the environment. Chatterjee’s doctoral work focuses on coating salt with a polymer membrane so that it still slows freezing but is not released into the environment.

Submitted by Rukmava Chatterjee

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