Any student who has taken an introductory chemistry lab course will remember identifying unknown substances by determining the temperature at which they melt. A student loads the mystery material into a glass capillary tube like those shown here, and then places it next to a thermometer in a heat-controlled light box called a Thomas Hoover apparatus (or the similar MelTemp). Then the student watches carefully and records the melting point, which is characteristic for any pure substance.
But it’s not just a teaching tool, many working scientists regularly use it. “Just another day in a medicinal chemistry lab,” says Malaika Argade, who snapped this photo in her Virginia Commonwealth University lab.
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