Iridium

Atomic Number: 77
Atomic Mass: 192.217

Iridium (chemical symbol Ir, atomic number 77) is one of the most remarkable and resilient metals on Earth. Known for its incredible resistance to heat and corrosion, it holds the distinction of being one of the most durable and rare elements in the periodic table. While it might not be widely recognized by the general public, iridium plays a critical role in some of the most demanding industrial and scientific applications, from aerospace to electronics and even the study of Earth’s history.

We’ll explore the discovery of iridium, its unique properties, and the wide-ranging applications that make this metal invaluable in the modern world.

The Discovery

Iridium was discovered in 1803 by British chemist Smithson Tennant in the residue left behind after dissolving platinum ore in acid. Alongside iridium, Tennant also discovered osmium, another rare and durable metal. The element was named iridium after the Latin word iris, meaning “rainbow,” because of the vibrant colors of its salts.

Iridium is one of the rarest elements in the Earth’s crust and is often found in platinum-group metals. It is mainly sourced as a byproduct of platinum and nickel mining, making it both scarce and valuable.

Properties of Iridium

Iridium is known for its extraordinary physical and chemical properties, making it an ideal material for high-performance and extreme-condition applications. Here are some of its key properties:

Second-Densest Metal: Iridium is the second-densest naturally occurring element, with a density of 22.56 g/cm³, just behind osmium. This gives iridium exceptional strength and durability.
Incredible Corrosion Resistance: Iridium is one of the most corrosion-resistant metals known, even in the presence of acids, alkalis, and high temperatures. It can withstand some of the harshest environments without degrading, making it suitable for use in extreme conditions.
High Melting Point: Iridium has an extremely high melting point of 2,446°C (4,435°F), making it ideal for use in high-temperature applications such as aerospace components and industrial equipment.
Brittleness: Despite its toughness and durability, iridium is relatively brittle, which can make it difficult to work with in its pure form. However, it is often alloyed with other metals to enhance its malleability.
Electrical Conductivity: Iridium is a good conductor of electricity, which, combined with its resistance to oxidation, makes it an important material in electrical contacts and electrodes.

Modern-Day Uses of Iridium

Iridium’s exceptional properties make it essential in a variety of highly specialized applications. Although it is rare and expensive, iridium is used where performance and durability under extreme conditions are paramount.

1. Aerospace and Rocket Technology

Iridium’s ability to withstand extreme temperatures and its resistance to corrosion make it a key material in aerospace applications. It is used in the production of engine components and thrusters for spacecraft and satellites, where materials are subjected to intense heat and stress. For example, iridium is often used in the ignition systems of rocket engines, where its durability ensures reliable performance during space missions.

2. Spark Plugs and Automotive Industry

Iridium is widely used in the automotive industry to make spark plugs that are longer-lasting and more efficient than traditional plugs made from other metals. Iridium-tipped spark plugs are highly durable and can withstand the high temperatures and wear experienced in internal combustion engines, improving engine performance and fuel efficiency. Because of this, iridium spark plugs are popular in high-performance and luxury vehicles.

3. Electronics and Electrical Contacts

In the electronics industry, iridium is used to create electrical contacts and electrodes in devices that must endure extreme conditions. Its corrosion resistance and conductivity make it valuable in high-precision components such as:

Electrical relays
Memory devices
Semiconductor devices

Iridium is also used in electrochemical cells and electroplating due to its ability to resist degradation over time, ensuring long-lasting performance.

4. Medical Devices

Iridium’s biocompatibility and durability have made it useful in medical devices. Iridium and its alloys are used in pacemakers and other medical implants because of their ability to resist corrosion and maintain stability inside the human body.

Iridium-based electrodes are also used in medical electrostimulation devices, providing reliable performance in treatments like deep brain stimulation for patients with neurological conditions.

5. Catalysis and Industrial Applications

Iridium is an important catalyst in the chemical industry, particularly in hydrogenation reactions. Iridium-based catalysts are used in refining processes and in the production of chemicals and pharmaceuticals, helping speed up important chemical reactions.

In glass manufacturing, iridium crucibles are used to mold glass at extremely high temperatures without contaminating the product. This makes iridium essential in the production of high-purity glass for fiber optics and other precision industries.

6. Studying Earth’s History: The Iridium Anomaly

One of the most interesting and unique uses of iridium comes from its role in studying Earth’s history. Iridium is rare in the Earth’s crust but more abundant in asteroids and meteorites. A layer of iridium-rich clay, known as the iridium anomaly, was discovered at the boundary between the Cretaceous and Paleogene periods (about 66 million years ago). This discovery led scientists to hypothesize that a massive asteroid impact caused the extinction of the dinosaurs. The presence of iridium in this layer provides a key piece of evidence supporting the asteroid impact theory.

The Challenges of Working with Iridium

While iridium’s properties make it incredibly useful, there are challenges associated with its use:

Rarity and Cost: Iridium is one of the rarest elements on Earth, making it expensive to produce and use. The limited availability of iridium, combined with the complexity of extracting it from platinum ores, drives up its cost, limiting its use to specialized applications.
Brittleness: Despite its incredible strength and resistance to corrosion, iridium is relatively brittle, which can make it difficult to shape and work with in its pure form. To overcome this, iridium is often alloyed with other metals like platinum.
Toxicity of Compounds: Some iridium compounds, such as iridium tetroxide (IrO₄), are toxic and volatile, requiring careful handling during industrial processes.

The Future of Iridium

Iridium will continue to play a key role in industries that demand materials capable of withstanding extreme environments. As space exploration advances and the demand for high-performance materials increases in industries like aerospace and electronics, iridium’s importance will only grow.

With increasing focus on sustainable technologies, iridium’s use in fuel cells and hydrogen production will likely become more prominent as industries search for ways to reduce carbon emissions and produce cleaner energy.

Additionally, continued research into iridium’s catalytic properties may lead to new innovations in chemical processing and industrial manufacturing, making iridium an even more valuable resource in the future.