The commercial use of high explosives in the excavating and mining industries was established by the inventions of dynamite and the blasting cap. Alfred Nobel mixed nitroglycerin, a very unstable high explosive, with silica powder, forming a stable paste that he called “dynamite.” Dynamite, which could be shaped into cylindrical charges that were safely detonated by a blasting cap, replaced black gunpowder, which had less than half of dynamite’s blasting power.
Dynamite is an absorbent material that has been soaked in nitroglycerin, a substance so unstable that it can easily explode with a slight impact or a small change in temperature or pressure, making it unsafe for practical use. Alfred Nobel found that the absorbent material—dynamite—stabilized the nitroglycerin to the point that it needed a detonator to trigger its explosive power. In 1863, he invented the blasting cap, a detonator that was triggered by a burning fuse. The smaller explosion of the blasting cap generated a shock wave that was sufficient to detonate the larger explosion of the nitroglycerin within the dynamite.
Nobel’s father, Immanuel Nobel, was an engineer and inventor. He built bridges and buildings in Stockholm, where the blasting of rocks was common practice. He also experimented with explosives, inventing and manufacturing naval mines made of black powder for the Russians during the Crimean War. Immanuel, who wanted his sons to join the family business, gave Alfred a first-class education. As part of his training in chemical engineering, Alfred researched explosives in the private laboratory of Théophile-Jules Pelouze
Explosives are materials that react extremely fast, producing a large amount of hot gas that expands so rapidly it creates a high-pressure wave. Some explosives, such as gasoline, utilize the oxygen in air to burn. The air-burning explosives react at such a slow rate that they are considered low-level explosives. The composition of high explosives already contains the oxygen needed for rapid “burning” within their chemical makeup, and their explosive reaction is considered a decomposition reaction. Nitroglycerin has a chemical formula of C
3
H
5
(ONO
2
)
3
; the oxygen in the compound combines with carbon and hydrogen and releases hot nitrogen gas during decomposition. The gases generated occupy more than twelve hundred times the original volume, and the heat generated by the reaction can raise the temperature to about 9,000 degrees Fahrenheit. The combined effect produces a local pressure of nearly 20,000 atmospheres that travels in a pressure wave at a speed of more than 17,000 miles per hour.
Early nitroglycerin was made by mixing glycerol with a mixture of sulfuric and nitric acids. The reaction that produced the nitroglycerin generated so much heat that it would cause the forming nitroglycerin to explode instantly. Attempts to run the reaction at cold temperatures were often unsuccessful because nitroglycerin is a liquid that would freeze at temperatures below 55 degrees Fahrenheit, and solid nitroglycerin is even more unstable than its liquid counterpart. Thus, Sobero
Alfred Nobel, along with his brother Emil
The use of nitroglycerin for blasting was now possible because of Alfred Nobel’s blasting cap, an igniter for the main explosion. The Nobel patent detonator used a strong shock rather than heat combustion to detonate the main explosive. His early blasting cap was a cylinder of black powder that was surrounded by a larger vessel containing the nitroglycerin. A burning safety fuse, of the type invented by William Bickford
The instability of nitroglycerin continued to be a safety problem. Nitroglycerin was an oily, highly volatile liquid that was soluble in alcohol but not water. Alfred mixed the nitroglycerin with diatomite. Diatomite is a natural sedimentary material made of microscopic shells from diatoms (algae) composed of silica (SiO
2
). The high porosity of the shells wicked the nitroglycerin into the microcavities, reducing the surface area for volatilization of the liquid. The silica shells protected the microscopic droplets from impact denotation, and the material now could be safely transported.
The mixture was a paste that could be molded by hand into cylindrical tubes that could easily be inserted into drill holes. The blasting caps could then be pushed and embedded into the paste. The impact of the explosion of the blasting cap would then detonate the pasty mixture of nitroglycerin and silica. Nobel called this new mixture dynamite and applied for a patent in 1867. In October of that year, Nobel received U.S. patent no. 78,317 for his dynamite.
Dynamite was soon recognized as the explosive of choice in the excavation and mining industries. Because it was impractical to transport explosives long distances and because of government restrictions on international shipments of explosives, dynamite had to be manufactured locally.
Luckily for Nobel, he was an excellent business entrepreneur. During the next two decades he founded or acquired more than ninety factories to produce dynamite in twenty different countries. So successful was Nobel that he became a multimillionaire. Many of his companies have become industrial enterprises that remain prominent in the world economy, including the Bofors-Gullspang Company in Sweden, a world-renowned manufacturer of munitions and firearms; Imperial Chemical Industries (ICI) of Great Britain; and Dyno Nobel in Norway.
Dynamite, detonated by a blasting cap, was the first high-explosive material that could be safely used for controlled blasting in the fields of civil engineering and mining. While dynamite saved thousands of lives in the long run, it was not free from causing accidents. The overall effects of blasting with dynamite increased, however, as fewer blasts were needed to accomplish the same amount of work.
Nobel’s work established the modern initiation sequence, or firing train, for the safe use of high explosives. The ignition sequence is a chain reaction that cascades from relatively low levels of energy (Nobel’s blasting cap) to the final detonation of the main charge of a high-energy explosive (Nobel’s dynamite). Although the explosives involved in the firing train have changed since their inception, the initiation sequence established by Nobel remains in use.
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Cooper, Paul W., and Stanley R. Kurowski. Introduction to the Technology of Explosives. New York: Wiley-VCH, 1997. Gives details on the explosive reaction for the decomposition of nitroglycerin, written for the nonscientist. -
Fant, Kenne. Alfred Nobel: A Biography. New York: Arcade, 1993. Tells the story of how Nobel invented dynamite and discusses his business ventures. -
Gleasner, Diana C. Dynamite: Inventions That Changed Our Lives. New York: Walker, 1982. Gives an account of the significance of the development of dynamite. Good for younger readers. -
Kelly, Jack. Gunpowder: Alchemy, Bombards, and Pyrotechnics: The History of the Explosive That Changed the World. New York: Basic Books, 2004. Relates the significance of dynamite’s replacement of gunpowder as the blasting material of choice in the 1870’s. -
Meyer, Rudolf, et al. Explosives. New York: Wiley-VCH, 2002. This reference book provides scientific details about 120 different explosive materials, including dynamite and nitroglycerin, although it lacks details on the chemistry and physics of explosives. Written for those with some knowledge of chemistry.
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Nobel Bequeaths Funds for the Nobel Prizes
Alfred Nobel; Bertha von Suttner.