On May 4, 1892 Thomas Willson, a Canadian inventor, placed some calcium oxide (lime), coal tar and aluminum oxide in a container and heated the mix to a high temperature. Willson was hoping to produce metallic aluminum, an expensive commodity at the time. The thinking was sound. Coal tar — basically carbon — was known to convert lime to metallic calcium. Willson knew that calcium was a more active metal than aluminum and he hoped that it would strip oxygen away from the aluminum oxide. After heating it he opened the furnace, hoping to see shiny metallic aluminum. Instead he saw a dark residue. Frustrated, he threw the residue into the stream running outside his lab. This, of course, was long before the existence of any environmental laws. It turned out to be a lucky thing.
As soon as the stuff hit the water, huge bubbles began to form and a plume of water shot up into the air. In an instant, disappointment changed into elation. Whatever Willson had made seemed more interesting than the aluminum he had sought. He repeated his experiment and, to his relief, produced the same residue, which once again produced gas when it reacted with water. Furthermore, the gas burned with a bright, sooty flame. It didn’t take long before chemical analysis showed that Willson’s residue was calcium carbide and the gas liberated on reaction with water was acetylene. The highly combustible acetylene was not a new discovery. Thirty years earlier, Friedrich Wohler, a chemistry professor from the University of Göttingen in Germany, had made calcium carbide by heating calcium with charcoal to a high temperature and observing that it formed acetylene when reacted with water. But Wohler’s method wasn’t an efficient way of making the carbide and hence not as useful for creating the gas on an industrial scale. Willson’s method yielded large amounts of calcium carbide and afforded a ready method for making acetylene.
So, why was this important? The 1890s was the era of the gaslight. The world’s first gaslight company had been established in London in 1813 and subsequently an elaborate network of gas lines had ensured that British city streets and homes could be well lit. But mobile lighting was still restricted to candles and kerosene lamps. Willson realized his acetylene, which burned with a more brilliant flame than kerosene, had great market potential. By 1895 he had founded a company that eventually became Union Carbide, one of globe’s biggest chemical companies. Soon, calcium carbide-based lamps appeared. They were clever devices in which water dripped into a container of carbide and generated acetylene gas. This in turn was channeled to a nozzle where it could be ignited. A mirrored surface behind the flame increased the intensity of the light.
Car manufacturers jumped on the idea, using carbide lamps for headlights. Miners also used the lamps, although not without risk. Combustible gases are often present in mines and in some cases were ignited by carbide lamps — with tragic results.
Today, carbide lamps have been relegated to the history books but acetylene is still one of the most important industrial chemicals in existence. In fact, modern life would not be possible without it. In 1895, the same year that Willson established his company, the French chemist Henry Louis Le Châtelier, a professor of chemistry at the College de France, discovered that when acetylene is burned with an equal volume of oxygen, the temperature of the flame — more than 3,000 C — was higher than that achievable by any other gas and hot enough to melt steel. The concept of welding was born. Without oxy-acetylene welding torches, construction, as we know it, would not be possible.
Acetylene has other uses as well. About half of all acetylene produced today goes towards the production of other organic chemicals. The addition of hydrogen cyanide to acetylene, for example, yields acrylonitrile, which is used in the production of acrylic fibres. Acetylene can also be converted into vinyl acetylene, the raw material needed to manufacture the synthetic rubber neoprene, a discovery credited to DuPont chemist Wallace Carothers of the United States.
And all of these inventions came about thanks to Canadian chemist Willson capitalizing upon a chance discovery.
Joe Schwarcz is the director of McGill University’s Office for Science and Society. Read his blog at www.mcgill.ca/oss.