Nitroglycerin, an oily fluid produced by reacting glycerin with nitric or sulfuric acid, was discovered by Ascanio Sobrero, a professor at the University of Turin in Italy, in 1847. Sobrero found “…its properties so unpredictable and frightening that he warned against its use” (DuPont 1980). Other discoveries that were important in formulating high — energy explosives are described in the following paragraphs.
Mercury fulminate was made in 1799 by reacting an excess of alcohol with a solution of mercury in nitric acid (Karrer 1947). The salt exploded violently when struck or
ignited and was soon used as a detonator in percussion caps (DuPont 1980). This was used in percussion caps in guns in 1814, but it was another 50 years before it was used in rock blasts.
Guncotton was the product of reactions between nitric and sulfuric acids and cotton. It was made by Christian Schonbein, a professor from the University of Basle in Switzerland, in 1845 and was more powerful, safer, and less corrosive than black powder (DuPont 1980). Its main use came when it was dissolved in nitroglycerin and formed a jelly that was used in gelatin dynamites.
By 1850, sufficient research had been done for a high-energy, detonating explosive to be made, but nothing happened until Immanuel and Alfred Nobel (see Chapter 2) recognized the potential value of nitroglycerin in 1859. Their interest in high-energy explosives caused them to investigate their manufacture and use, and they were sufficiently impressed by nitroglycerin that they borrowed 100,000 francs to build a factory in Sweden. It was easy enough to make the oil but there were many problems in using it. For example, the oil had to be poured into fissures in the rocks (mechanical drills were unavailable), and there were losses of explosive in the rock masses and danger in the undetonated remnants of the broken products. In addition, potentially dangerous leakage occurred during storage and transport.
Alfred Nobel systematically investigated the possibilities for making the best use of nitroglycerin. After experimenting with detonating mixtures of nitroglycerin and black powder under various conditions, he concluded that the full effect of nitroglycerin as an explosive could only be obtained by detonating it with a compound such as mercury fulminate that was exploded in close proximity (Drinker 1888). The market for nitroglycerin explosives was brisk but premature explosions still made safety a serious problem. In 1867, Nobel observed that the mineral kieselguhr packed around containers of nitroglycerin absorbed leaking explosive. He made a solid nitroglycerin-kieselguhr mixture containing 25% kieselguhr (McAdam and Westwater 1958) into cartridges which themselves had strong explosive properties. He called the product dynamite and demonstrated that dynamite could be handled safely and detonated when required. With its discovery “The blasting of roads and mines now entered a new era, as did the military art” (Halasz 1959). In another development Nobel combined guncotton with nitroglycerin to make a very powerful explosive that he called blasting gelatin.
Dynamite was quickly found in practice to be effective for breaking and moving rocks because of its high detonation velocity and explosive power. The two explosives, black powder and dynamite, were extensively used until 1920 when dynamite started to take over the market and became dominant by 1950.