Nobel’s explosive recipe for peace

Alfred Nobel hoped that his invention of dynamite would bring an end to war,
writes Steve Jones

Next month, the Nobel committee will announce the winners of this year’s prizes. The peace prize, especially, is odd, for it comes from the profits of war. Alfred Nobel was the inventor of dynamite, the power of which comes from the chemistry of a substance that surrounds us all. This element was isolated in Scotland, but its properties were first appreciated in 18th-century France, where Antoine Lavoisier baptised the stuff as azote (which means “lifeless”, for animals cannot survive in it). We know it as nitrogen.

Nitrogen gas, which makes up 80 per cent of the air, is extremely stable. However, it has hidden powers. They spring from its reluctance to form compounds with other elements unless forced to do so by heat, pressure, powerful chemicals, or complex biological tricks. That is because nitrogen has a valency – a bonding power – of three. The oxygen in the atmosphere consists of a pair of atoms joined by a double bond; the nitrogen also comes in pairs, but this time held by three connections. Those ties are strong – but when they break, nitrogen will fall into bed with anything that will have it, making laughing gas, cyanide, superglue and more. It is particularly happy to combine with oxygen to generate the raw material of dynamite and its fellows.

Gunpowder is a mixture of relatively innocuous chemicals: saltpetre, charcoal and sulphur. The charcoal and sulphur act as fuels, while, given a suitable push, the nitrogen, oxygen and potassium in the saltpetre break their bonds, allowing the liberated oxygen to ignite the other ingredients and produce an expanding wave of gas. Plenty of nitrate salts do the same, often with greater power (as in the typical car bomb, which is made of ammonium nitrate mixed with fuel oil).

Nobel’s fortune began with a more ticklish reaction. Nitroglycerine is made by cautiously adding glycerine to nitric and sulphuric acid. If you try this at home, make sure to keep the mixture in an ice bath – but not to let it freeze, for it becomes even more unstable. A spark or even a slight tap can set it off. When it does so, the shock wave travels at 30 times the speed of sound – far faster than in gunpowder – and the chemical expands by more than 1,000 times.

Nobel’s factory became the main producer of the stuff, which was used, for example, to allow railroads to blast their way across the Rockies. It also caused many lethal accidents. In 1864, one blew up Nobel’s younger brother, Emil.

Alfred set out to find a safer alternative, which would make nitroglycerine less susceptible to shock while retaining its explosive power. He found the key in the fossilised skeletons of tiny marine creatures. They became a porous soil called kieselguhr, which soaked up the lethal oil and made it far more stable. In 1867, he patented this “dynamite” and became fabulously rich.

To today’s armies, dynamite and its relatives are old hat. Their new toys are far more powerful. But they still depend on the same process, disrupting salts of nitrogen arranged in complicated cage-like structures held together with dense multiple bonds.

Octanitrocubane, for example, is a cube of carbon atoms, each attached to nitrogen and oxygen. Carbon prefers to make structures with an angle of 109 degrees between each atom (as in a diamond), rather than the right angles it is forced into here. When detonated, the energy stored in these strained bonds is released, as are vast volumes of carbon dioxide and nitrogen, to produce a shock wave travelling at six miles a second.

Nobel hoped that dynamite would put an end to war, as no one would dare to use such a lethal substance because of the dangers of retaliation. There he was wrong, for the chemistry of killing has become a science of its own. When physics took over, however, the atomic weapons that resulted were so terrifying that he was, more or less, proved right. How long that will last, no one knows.