Karl Herzfeld

Karl Ferdinand Herzfeld was an Austrian–American physicist and chemist. He worked on condensed matter physics, fluid dynamics, and statistical mechanics. In 1927, he was the first to quantify when a substance is a metal or an insulator. The Goldhammer–Herzfeld criterion to classify metalloids is named after him. With Frank O. Rice, he studied the rate equations of the pyrolysis of acetaldehyde in 1934. Their model is known as the Rice–Herzfeld mechanism.