History's Hidden Fire

SHORT TAKES

GUNPOWDER: Alchemy, Bombards & Pyrotechnics: The History of the Explosive That Changed the World, by Jack Kelly, Basic Books, 2004, 261 pages, $25 (ISBN 0-465-03718-6)

Among books that strive to show how a single substance changed the course of history, Jack Kelly's new history of gunpowder makes a compelling case. By Kelly's account, the destructive power of gunpowder--an explosive mixture of saltpeter, sulfur, and charcoal--fueled the West's imperial aspirations, spurred the creation of modern nation-states, and helped usher in the Industrial Revolution.

In tracing gunpowder's story, Kelly--an accomplished novelist and an experienced author of popular history--paints a vivid picture of the alchemists who created the substance and the chemists who tried to understand and manipulate it.

Gunpowder dates back to the ninth century, when Chinese alchemists searching for an elixir of immortality were dismayed to find that a mixture of saltpeter (potassium nitrate), honey, sulfur, and arsenic sulfide erupted in smoke and flame. A modified version of this curious concoction soon found use as a magician's trick. It wasn't until the early-11th century that the Chinese began to find military purposes for gunpowder, using it to make incendiary and smoke bombs. But by the 13th and 14th centuries, the Chinese were wielding cannons and guns that harnessed the explosive power of gunpowder to hurl projectiles at enemy forces.

Europeans soon learned of gunpowder and sought to make it themselves. But the availability of saltpeter, gunpowder's primary ingredient, remained the sticking point: Saltpeter is a by-product of soil bacteria that decompose decaying organic material, and China had plenty of it. Europe was not so lucky. Hoping to lessen their dependence on imported saltpeter, European powder makers began to "farm" saltpeter by composting human feces, horse dung, urine from drunks, and lime. After the dung heap had aged, what remained was soaked in water, and the resulting CaNO₃-enriched liquor was mixed with K₂CO₃-rich wood ashes to give a KNO₃-enriched solution that could be evaporated to yield mostly KNO₃.

But as Kelly points out, this process was the result of trial and error, not rational scientific experiment. Powder makers had also relied on trial and error to identify what turned out to be the ideal gunpowder recipe: 75% saltpeter, 15% charcoal, and 10% sulfur. In fact, up until the mid-17th century, scientists still believed that fire was an element hidden within gunpowder. Kelly provides a compelling if not detailed description of the chemists who dispelled this theory and sketches a succinct explanation of the chemical mechanism of the explosive.

Eventually, world demand for gunpowder skyrocketed--both for military and commercial purposes--pushing gunpowder manufacturers to rationalize production. In describing the industry's maturation, Kelly recounts the earliest days of the chemical company DuPont, which began its life as a gunpowder manufacturer in 1804. During the Civil War, DuPont chemists devised a chemical process to convert dirt-cheap and abundant NaNO₃ from Chile into KNO₃. Sodium nitrate worked nearly as well as KNO₃ in gunpowder but readily absorbed moisture, preventing ignition. Later, the company patented a way to make NaNO₃-based gunpowder moisture resistant.

The book also gives a striking account of chemists' struggle to find a chemical replacement for gunpowder. Eventually, dynamite (a mix of nitroglycerin and diatomaceous earth) supplanted gunpowder for blasting mines and tunnels. By the 1890s, "gunpowder" had come to refer to a smokeless synthetic powder made of nitroglycerin, nitrocellulose, and petroleum. Today, smokeless powder is the propellant of choice in guns. Traditional gunpowder--now known as "black powder"--is still used in fireworks, antique guns and cannons, and modern muzzle-loading rifles.

If you are a history fan or a military buff, you will find a lot to love in Kelly's book. But even if you're not, it's worth a read for the fascinating chemical story he has woven.