Rhenium: From Volcanoes to Jet Engines — A Periodic Videos Deep Dive

Overview

In this Periodic Videos episode, the team investigates rhenium, one of the hardest metals with a key role in turbine blades for jet engines. The story spans dense pellets, industrial recycling, and a rare mineral discovered in volcanic vents.

• Key insights: Rhenium's hardness and high melting point drive turbine alloy performance
• Discovery history including Ogawa, Ide Tucker, and Nodak
• Rare mineral rheniite found in a Kuril Island volcanic fumarole
• Recycling through ammonium perrhenate and oxide chemistry demonstrations

Introduction to Rhenium and Its Importance

Rhenium is highlighted as one of the most durable metals with a very high melting point, making it a crucial component in turbine blades used in jet engines. While not used in pure form, rhenium is alloyed with other metals to enhance performance and durability. The video also introduces ammonium perrhenate as a compound used to purify and recycle rhenium due to its industrial scarcity.

The Discovery Tale: From Periodic Table to Industrial Scale

The history of rhenium’s discovery unfolds with early misinterpretation by the Japanese chemist Ogawa who believed he had isolated element 43, later realized to be 75, now known as technetium. After World War I, Ide Tucker identified the missing element through X-ray evidence, confirmed by later work with Nodak. Industrial-scale isolation expanded after the war, particularly from Kazakhstan, contributing to early uses in rocket nozzles. This narrative underscores how scientific tools and historical events shape the discovery and application of elements.

The Advent of Rheniite: A Mineral Dominated by Rhenium

One of the video’s highlights is the discovery of rheniite, a mineral with unusually high rhenium content. Detected on the Kuril Islands after the collapse of the Soviet Union, the crater vents of Kudryavo volcano release vapors containing rhenium. The mineral was described in Nature and photographed in a famous piece explaining its significance. A rare sample of rheniite, loaned through the Natural History Museum, is featured in the host’s hands to illustrate its metallic sheen and rarity.

Volcanoes, Vapor, and Mineral Formation

The video explains two key factors for rhenium deposition in volcanogenic settings: the presence of rhenium deep inside the volcano and the unique vent configuration that allows high-temperature steam to carry and react oxides of rhenium with hydrogen sulfide, yielding the arenium-like mineral rare in nature. This collaboration between geology and geochemistry demonstrates how volatile oxides can behave differently from the native metal, enabling selective mineral formation in extreme environments.

From Volcano to Laboratory: Experiments and Observations

Demonstrations include heating rhenium pellets in a Bunsen flame, where a green flame suggests the presence of rhenium’s atomic spectrum, followed by the appearance of white smoke indicating oxide vaporization. The pellet develops a black oxide coating after cooling, while a cleaned pellet heated at a lower temperature forms a red coating consistent with rhenium trioxide REO3. These observations illustrate oxide volatility and surface chemistry, contrasting with the metal’s apparent inertness under certain conditions.

Recycling, Volatility, and Industrial Prospects

Geologists imagined the possibility of mining rhenium from volcanic gases, estimating potential yields around 20 tons annually from a single volcano. However, practical extraction proved far more challenging, yielding only tens of grams and revealing the complexities of extracting rhenium from volatile oxides in an industrial setting. The discussion underscores both the potential and the limits of in-situ mineral mining from volcanic emissions.

Closing Notes: Fluorescence and Public Engagement

To celebrate rhenium’s chemistry, the team showcases a bright yellow rhenium phenanthroline complex, which fluoresces under UV light. A visit to Neil’s office reveals Brady’s reaction to the vivid complex, highlighting how rhenium chemistry can capture attention with colorful, photoluminescent behavior.