1883

Liquid Nitrogen

Johann Gottlob Leidenfrost (1715–1794), Zygmunt Wróblewski (1845–1888), Karol Olszewski (1846–1915)

Nitrogen is the most abundant gas on earth, but it’s a gas only because of the relative warmth of our planet. If you can cool it down to −321 degrees Fahrenheit (−196 degrees Celsius), it will condense into a thin, clear liquid. In 1883, Polish physicist Zygmunt Wróblewski and his colleague, the Polish chemist Karol Olszewski, first accomplished that feat, in Kraków, Poland. Using a laborious series of cooling and suddenly expanding of the gas, they were only able to produce small amounts, however.

Condensing nitrogen into the liquid state is a complex process (see Liquid Air), and its larger-scale production had to wait until the 1890s, with several more decades passing before liquid nitrogen became a common industrial chemical. Nontoxic, odorless, colorless, and nonflammable, this abundant gas is the most widely used cryogenic substance in the world, helping to cool down superconducting magnets for NMR (nuclear magnetic resonance) machines, cooling the traps of vacuum pumps (used in many scientific and industrial processes), and freezing tissue samples for medical research, as well as other applications. It’s also crucial in many chemical reactions as well as food packaging, and its use has recently become popular among high-tech chefs.

In the lab, liquid nitrogen is often bubbling violently, simply because almost anything will warm it up enough to start it boiling away. It doesn’t cool a warm object down as quickly as you might think, though, because a layer of vapor quickly forms and insulates it. This is known as the Leidenfrost effect, a phenomenon first described by German doctor Johann Gottlob Leidenfrost in 1756. Home cooks encounter it when flicking drops of water onto a hot griddle to test its temperature. In the same way, small amounts of liquid nitrogen will roll off the skin on contact—but beware, any more can cause painful and dangerous frostbite. Entertaining demonstrations of the effects of liquid nitrogen for students often include the quick freezing of common objects, leading to popular effects like the “shattering rose” and the “banana hammer,” which more or less explain themselves.

SEE ALSO Liquid Air (1895), Neon (1898), NMR (1961)

In recent years, liquid nitrogen has become a favorite of avant-garde chefs and home-kitchen experimenters because it will produce unusual frozen concoctions in record time.