LIQUID NITROGEN - Liquid nitrogen is the liquefied form of the element nitrogen that's produced commercially by the fractional distillation of liquid air. Liquid nitrogen is stored in special insulated containers that are vented to prevent pressure buildup. Liquid nitrogen boils so rapidly that it surrounds surfaces with an insulating layer of nitrogen gas. This is why spilled nitrogen droplets skitter across a floor. When working with liquid nitrogen, taking safety precautions is paramount: Liquid nitrogen is cold enough to cause severe frostbite on contact with living tissue. You must wear proper safety gear when handling liquid nitrogen to prevent contact or inhalation of the extremely cold vapor. Cover and insulate skin to avoid exposure. Do not enclose liquid nitrogen in a sealed container, as this may result in it bursting or an explosion. Adding large quantities of nitrogen to the air reduces the relative amount of oxygen, which may result in an asphyxiation risk.

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Liquid Nitrogen Facts

Uses, Dangers, and Safety Precautions

Anne Marie Helmenstine, Ph.D.

Liquid nitrogen is a form of the element nitrogen that's cold enough to exist in a liquid state and is used for many cooling and cryogenic applications.

Here are some facts about liquid nitrogen and crucial information about handling it safely.

Liquid Nitrogen Facts

Liquid nitrogen is the liquefied form of the element nitrogen that's produced commercially by the fractional distillation of liquid air.

Like nitrogen gas, it consists of two nitrogen atoms sharing covalent bonds (N2).

Sometimes liquid nitrogen is denoted as LN2, LN, or LIN.

A United Nations Number (UN or UNID) is a four-digit code used to identify flammable and harmful chemicals. Liquid nitrogen is identified as UN number 1,977.

At normal pressure, liquid nitrogen boils at 77 K (−195.8° C or −320.4° F).

The liquid-to-gas expansion ratio of nitrogen is 1:694, which means liquid nitrogen boils to fill a volume with nitrogen gas very quickly.

Nitrogen is non-toxic, odorless, and colorless. It is relatively inert and is not flammable.

Nitrogen gas is slightly lighter than air when it reaches room temperature. It is slightly soluble in water.

Nitrogen was first liquefied on April 15, 1883, by Polish physicists Zygmunt Wróblewski and Karol Olszewski.

Liquid nitrogen is stored in special insulated containers that are vented to prevent pressure buildup. Depending on the design of the Dewar flask, it can be stored for hours or for up to a few weeks.

LN2 displays the Leidenfrost effect, which means it boils so rapidly that it surrounds surfaces with an insulating layer of nitrogen gas. This is why spilled nitrogen droplets skitter across a floor.

Liquid Nitrogen Safety

When working with liquid nitrogen, taking safety precautions is paramount:

Liquid nitrogen is cold enough to cause severe frostbite on contact with living tissue.

You must wear proper safety gear when handling liquid nitrogen to prevent contact or inhalation of the extremely cold vapor. Cover and insulate skin to avoid exposure.

Because it boils so rapidly, the phase transition from liquid to gas can generate a lot of pressure very quickly.

Do not enclose liquid nitrogen in a sealed container, as this may result in it bursting or an explosion.

Adding large quantities of nitrogen to the air reduces the relative amount of oxygen, which may result in an asphyxiation risk.

Cold nitrogen gas is heavier than air, so the risk is greatest near the ground. Use liquid nitrogen in a well-ventilated area.

Liquid nitrogen containers may accumulate oxygen that is condensed from the air. As the nitrogen evaporates, there's a risk of violent oxidation of organic matter.

Liquid Nitrogen Uses

Liquid nitrogen has many uses, mainly based on its cold temperature and low reactivity. Examples of common applications include:

The freezing and transporting of food products

The cryopreservation of biological samples, such as sperm, eggs, and animal genetic samples

Use as a coolant for superconductors, vacuum pumps, and other materials and equipment

Use in cryotherapy to remove skin abnormalities

The shielding of materials from oxygen exposure

The quick freezing of water or pipes to allow work on them when valves are unavailable

A source of extremely dry nitrogen gas

The branding of cattle

The molecular gastronomy preparation of unusual foods and beverages

The cooling of materials for easier machining or fracturing

Science projects, including making liquid nitrogen ice cream, creating nitrogen fog, and flash-freezing flowers and subsequently watching them shatter when tapped onto a hard surface.

Anne Marie Helmenstine, Ph.D.

Introduction

Ph.D. in biomedical sciences from the University of Tennessee at Knoxville - Oak Ridge National Laboratory.

Science educator with experience teaching chemistry, biology, astronomy, and physics at the high school, college, and graduate levels.

ThoughtCo and About Education chemistry expert since 2001.

Widely-published graphic artist, responsible for printable periodic tables and other illustrations used in science.

Experience

Anne Helmenstine, Ph.D. has covered chemistry for ThoughtCo and About Education since 2001, and other sciences since 2013. She taught chemistry, biology, astronomy, and physics at the high school, college, and graduate levels. She has worked as a research scientist and also abstracting and indexing diverse scientific literature for the Department of Energy.

In addition to her work as a science writer, Dr. Helmenstine currently serves as a scientific consultant, specializing in problems requiring an interdisciplinary approach. Previously, she worked as a research scientist and college professor.

Education

Dr. Helmenstine holds a Ph.D. in biomedical sciences from the University of Tennessee at Knoxville and a B.A. in physics and mathematics with a minor in chemistry from Hastings College. In her doctoral work, Dr. Helmenstine developed ultra-sensitive chemical detection and medical diagnostic tests.

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