Safe Enough to Kill: Advances in the Chemistry of Explosives

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Safe Enough to Kill: Advances in the Chemistry of Explosives

Overview

Warfare took a deadly step forward with the invention and development of powerful explosives in the nineteenth century. Guncotton and a safer explosive, cordite, supplied a "smokeless" propellant that made the battlefield visible. Big explosions became more practical when Alfred Nobel stabilized nitroglycerin by converting it to dynamite. But while mass destruction was made easier, so was mining, the drilling of oil wells, and reshaping the land for roads, railroads, and construction. The understanding of nitrogen chemistry that came from research into explosives built a basis for creating new fertilizers and medicines. While Nobel's hope that dynamite would end war by making it too horrible to engage in was proven wrong, his prizes have provided the twentieth century's most visible recognition for contributions to peace, as well as to science and literature.

Background

Explosives research emerged from advances in the general understanding of chemistry. Scientists such as Jöns Berzelius (1779-1848) were eager to figure out how new materials might be created by combining familiar materials. In fact, Berzelius, who discovered three elements, began the practice of using compact symbols for elements, so that familiar formulations such as H₂O for water and C₆H₁₂O₆ for glucose. This contribution helped chemists to reveal and clearly articulate how chemicals combined and rearranged to form new compounds. Explosives became a serious area of chemical research when Ascanio Sobrero (1812-1888), who had studied under Berzelius, discovered nitroglycerin in 1847. Sobrero slowly added glycerin to a mixture of nitric and sulfuric acids and observed that adding a small amount of heat to the new compound created a big bang. He was horrified by his discovery, and, while he reported the powerful effects of nitroglycerin, he never tried to put it to use.

Others were less cautious. Even though nitroglycerin is highly unstable and extremely dangerous to manufacture and use, its power proved irresistible. One person who was attracted to it was Alfred Nobel (1833-1896). Nobel had grown up with weapons. His father moved the family to Russia to create underwater mines and machine tools for the Tsar. With the end of the Crimean War, the family's business was having difficulties, and Nobel saw the advantage of developing a better form of nitroglycerin. One of his first contributions was the invention of a detonator for the explosive. He began to manufacture nitroglycerin in his native Sweden, but when a factory blew up, killing several people including his brother, Nobel was banned from rebuilding his factory. Undeterred, Nobel set up a laboratory on a barge in the middle of a lake. There he had a lucky accident. In 1866 some nitroglycerin leaked into a container filled with diatomaceous earth (kieselguhr). The combination, called dynamite, was stable. It could not be jarred into action, but once ignited with a blasting cap (a smaller explosive, also invented by Nobel), it had the full power of the original nitroglycerin.

Luck and Alfred Nobel are connected with another development in the chemistry of warfare, the invention of smokeless powder. Battlefields at the beginning of the nineteenth century were overhung with a cloud of black smoke. Gunpowder creates a dirty explosion, and the combined firings of many guns and cannons often meant that troops were fighting blind. Unless they had favorable winds, generals could not effectively direct their troops. An accident set off a change in this situation in 1845. Christian Schönbein (1799-1868) did basic research in chemistry and is known for the discovery of ozone. Schönbein had been forbidden from conducting experiments in his wife's kitchen, but he was doing so anyway. While he was combining nitric acid and sulfuric acid, he spilled the mixture. He needed to clean it up before his wife came back, so he grabbed her cotton apron, mopped up the mixture, and set the apron next to the stove to dry. Unexpectedly, the apron disintegrated. Schönbein had created guncotton.

Unlike Sobrero, Schönbein had no qualms about putting his invention to use. In fact, he rushed guncotton into production as a "smokeless" (in reality merely lower smoke) alternative to gunpowder. Like nitroglycerin, however, guncotton proved to be deadly to manufacture and use. Ultimately, after the explosion of a few factories, it fell out of favor. It was two British scientists who took on the problem of creating a safer alternative.

Frederick Abel and James Dewar (1842-1923) were practical men, and their work in explosives was deliberate, not accidental. While both were interested in fundamental aspects of chemistry, they relied on defense work to provide a steady income. Together, they set out to create a smokeless propellant that had the same stability as dynamite. The combination was not obvious and the work was dangerous and disappointing. Dewar actually met with Nobel to discuss the project. (Nobel had produced his own smokeless powder, ballistite.) It was soon afterward that Abel and Dewar mixed nitroglycerin, guncotton, and vaseline to create cordite. Cordite first exists as a liquid that can be extruded and dried to create cords (hence its name). These cords, like dynamite, are highly stable and do not present the same dangers as guncotton. Cordite's burn rate can be fine tuned by modifying the shape of the grains. The cords also can be measured out and conveniently cut to the desired length to create exactly the right size of explosion. The Spanish-American War (1898) was the last major conflict fought without smokeless powder.

Impact

Dynamite and cordite did not introduce the world to massacres. The American Civil War's Battle of Antietam (1862), for instance, left 23,000 soldiers dead, wounded, or missing in a single day. But dynamite and cordite did allow for massive stockpiling of the first weapons of mass destruction. When the "powder keg" was ignited during World War I, eight and a half million people were killed. The world was horrified by what was incorrectly called "the war to end all wars." Today, explosives are as popular as ever. In 1995 almost five billion tons of explosives and blasting agents were produced in the United States alone.

Explosives also found peaceful uses. Nobel, who studied in the United States, was inspired in his work by the possibilities he saw in taming the American West. In fact, the efficient road, railroad, and tunnel systems that connect people today would not have been possible without dynamite. Dynamite has been essential to unlocking resources. Nobel himself benefited from the use of his explosive to improve oil production in Russia, and E.A.L. Roberts received a patent in the U.S. for using dynamite to unlock reserves of pools of oil. All types of mining have been facilitated as well, making the coal, stone, and metals that are essential to modern life available at affordable prices.

The explosive reshaping of our planet through the creation of roads, tunnels, and dams, not to mention strip-mining and the burning of coal, has also led to cases of environmental devastation. Today in many developed nations, limits—such as environmental impact statements—have been placed on development activities and the use of natural resources. But through most of the history of modern explosives, the users have been heedless of the environmental consequences of their use. As a result, there have been many cases where species and ecosystems have been made extinct by explosive-facilitated development.

A less apparent effect of research into explosives has been progress in nitrogen chemistry. Gunpowder, guncotton, nitroglycerin, cordite, and dynamite all depend on nitrogen compounds. As chemists have worked to harness the explosive power of these materials, they have come to a better understanding of the chemical properties of nitrogen. Nitrogen is the most abundant chemical in the air (in the form of N₂, nitrogen gas). It is also the basis for fertilizers, which helped turn aside nineteenth-century predictions of worldwide starvation by dramatically improving agricultural yields. In the early 1900s Fritz Haber (1868-1934) developed a Nobel Prize-winning process for "fixing" atmospheric nitrogen, creating a synthetic source of material for the production of both fertilizers and explosives. The work of this chemist (who was also a weapons developer involved in gas warfare) would not have been possible without the earlier work of chemists exploring nitrogen compounds for their explosive properties. Nitrogen chemistry has also led to the creation of new medicines. Nitroglycerin itself has found widespread pharmaceutical use as a vasodilator—it dilates, or enlarges, blood vessels—and is taken by people with angina pectoris to relieve their chest pains.

An indirect effect of nineteenth-century advances in the chemistry of explosives came from the wealth accumulated by Alfred Nobel. The production and sale of dynamite was highly profitable but controversial. Nobel was called "the merchant of death." Perhaps concerned about his legacy, Nobel at his death left more than nine million dollars (an enormous sum at the time) in trust to finance yearly awards for achievement in chemistry, physics, medicine, literature, and peace. (Economics was not provided for in Nobel's will but was added later.) These have become the most prestigious awards in their disciplines and now have a cash value of more than one million dollars each. They have motivated brilliant and powerful people and made the public aware of significant achievements.

PETER J. ANDREWS AND SCOTT BOHANON