By the 1860s, nitroglycerin was recognized as a powerful explosive but was notoriously unstable and prone to detonating from shock during transport. In 1867, Alfred Nobel patented dynamite after discovering that mixing nitroglycerin with a particular substance made it far safer to handle without weakening its explosive power. What was that substance, and why did it work?
- Powdered charcoal, which chemically neutralized the compounds in nitroglycerin responsible for its sensitivity to shock
- Kieselguhr, a porous, absorbent silica-rich earth that soaked up the liquid nitroglycerin into a dry, stable, granular paste
- Purified beeswax, which coated each droplet of nitroglycerin in a flexible film that cushioned it from shock
- Powdered limestone, which reacted with nitroglycerin to form a chemically inert compound that had to be reactivated with a blasting cap before use
Why B? And why not the others?
Correct answer: B. Kieselguhr, a porous, absorbent silica-rich earth that soaked up the liquid nitroglycerin into a dry, stable, granular paste
Nobel discovered, by chance, that liquid nitroglycerin was absorbed to dryness by kieselguhr, a porous siliceous earth, purely through physical soaking rather than any chemical reaction, turning the notoriously shock-sensitive liquid into a dry, granular, moldable solid that was resistant to shock but still readily set off by heat or percussion; he patented the result, named dynamite, in Britain in 1867 and the United States in 1868. The option describing powdered charcoal chemically neutralizing shock-sensitive compounds is wrong because no such chemical neutralization occurs; the kieselguhr mechanism is physical absorption, not a chemical reaction with nitroglycerin's structure. The option describing beeswax coating each droplet is wrong because no coating or cushioning film is involved; the earth simply soaks up the liquid throughout its porous structure. The option describing limestone forming an inert compound needing reactivation is wrong on two counts: no chemical reaction with limestone occurs, and dynamite required no separate reactivation step beyond the blasting cap used to detonate any stick.
Source: Britannica: dynamite; Alfred Nobel