Summary
Highlights
The speaker reminisces about his childhood, observing a strange man selling purple tablets at Shepherd's Bush market, claiming they could cure any ailment. This sets the stage for exploring how perceptions and understanding of substances have evolved.
About 300 years ago, scientists realized air consists mainly of two gases: oxygen, responsible for burning, and nitrogen. They identified that approximately one-fifth of the air is oxygen and began experimenting to make fuels burn more efficiently by combining them with oxygen.
Cotton, a natural fiber known for over 5,000 years, originated and was widely used in India and Mexico. Chemically, cotton is cellulose, a natural polymer valued for its comfort and warmth. It played a significant role in the Industrial Revolution in the 18th century. Simple burning of cotton in air (which is only 20% oxygen) results in an unspectacular, incomplete combustion, leaving ash.
In the mid-19th century, chemists experimented with adding oxygen to fuels. Ascanio Sobrero and Christian Schönbein independently achieved remarkable results by treating cotton with a mixture of nitric and sulfuric acid. This process infused cotton with additional oxygen, increasing its weight significantly (e.g., from 1.7g to 2.8g in one example). Despite no visible or tactile change, the treated cotton burns almost instantly and completely, demonstrating a successful chemical alteration.
Guncotton, also known as nitrocellulose, is a highly dangerous high explosive used in engineering and military applications. The speaker explains that while a direct explosion is too risky for a demonstration, he will show propulsion instead. Propulsion is a directed explosion, where gases are rapidly released in one direction, unlike an explosion which releases gases everywhere. He plans to demonstrate this by launching ping-pong balls with a mortar-like device, similar to how fireworks are propelled.