Scientists crack the 400-year-old enigma of gold’s purple smoke

Selected Area Electron Diffraction ring pattern from gold nanoparticles. The rings are indexed to Au as per the Joint Committee on Powder Diffraction Standards (JCPDS) card no. 04-0784. Credit: arXiv (2023).

In a significant scientific breakthrough, a team from the University of Bristol has finally solved a centuries-old mystery: why does fulminating gold, an explosive known since the 16th century, produce a purple smoke upon detonation?

This discovery, cracking a puzzle that has intrigued scientists since the days of alchemy, sheds new light on the fascinating world of early explosives.

First discovered by alchemists in the 1500s, fulminating gold was the world’s first known high explosive.

It’s a mixture of various compounds, with ammonia being a key ingredient contributing to its explosive nature.

Despite being known and studied for centuries, one question about fulminating gold remained unanswered: what causes the purple smoke released upon its explosion?

The peculiar purple smoke was first noted by German alchemist Sebald Schwaertzer in 1585.

Over the years, the phenomenon caught the attention of prominent chemists like Robert Hooke and Antoine Lavoisier. Yet, the cause of this colorful display remained a mystery.

Fast forward to the present day, Professor Simon Hall and his Ph.D. student Jan Maurycy Uszko from the University of Bristol took on the challenge of solving this enigma. Professor Hall expressed his excitement about the team’s contribution to understanding this historic material.

Their innovative experiment involved creating fulminating gold and detonating small quantities of it on aluminum foil. They then captured the resulting smoke using copper meshes for detailed analysis.

Under a transmission electron microscope, the team made a groundbreaking discovery. The purple smoke contained spherical gold nanoparticles.

This confirmed the long-held but unproven theory that the coloration was indeed due to gold playing a role in the smoke’s formation.

Having unraveled the secret of fulminating gold’s purple smoke, Professor Hall and his team are not stopping there.

They plan to apply this methodology to study the clouds produced by other metal fulminates, including platinum, silver, lead, and mercury. These substances, used throughout history, still hold unanswered questions about their explosive behaviors.

For those interested in the intricacies of this discovery, the team’s research paper, titled “Explosive Chrysopoeia,” is available on the arXiv.

Key Takeaways

This breakthrough by the University of Bristol team not only solves a historical puzzle but also enriches our understanding of early explosives.

The discovery that the striking purple smoke of fulminating gold is due to gold nanoparticles opens new doors in the study of explosive materials and continues to bridge the gap between ancient alchemy and modern chemistry.