Cool it, with a pinch of salt

Melting a solvent with a salt and then desalinating it enables a reversible cooling cycle In countries with harsh winters, putting salt on roads transforms ice into slush. Adding salt depresses the freezing point of water. In other words, ice gets colder when salt is added. How much colder? The surface of ice cubes covered with kitchen salt reaches −10°C after a few seconds, whereas ice cubes of pure water remain at 0°C. Lilley and Prasher (1) revisited this cooling principle, and on page 1344 of this issue, they describe how to make it reversible. The idea behind this “ionocaloric” refrigeration is to take advantage of the large temperature change—and therefore the large heat absorption—obtained by melting a “special ice” when put in contact with a specific salt. The authors made this cooling process reversible to achieve an efficient cycle with potential wide applications in refrigeration.