Source of information: ttp://mysite.du.edu/~jcalvert/phys/bang.htm#Arom
In 1838 M. Pelouze treated cotton with concentrated nitric acid, producing cellulose nitrate, a substance later called guncotton. In 1845, Schonbein showed that the nitration could be accelerated by mixed nitric and sulphuric acids, and dreamed that guncotton could replace black powder. This new explosive proved very unpredictable. In 1847, a guncotton factory exploded in England. Von Lenk worked for years in Austria to adapt guncotton to ballistics, but explosions in 1862 and 1865 put an end to his experiments. Not until 1865 did Sir Frederick Abel at Woolwich Arsenal finally produce a safe guncotton, by rigorously purifying the raw materials and carefully controlling the manufacturing process. Guncotton was a much more powerful explosive than black powder, but it was difficult to use. E. O. Brown showed that moist guncotton (which was relatively safe) could be exploded by a little dry guncotton (which was sensitive to shock) and a detonator. Guncotton releases about 1100 kcal/kg, nearly twice the heat of black powder, and two-thirds that of nitroglycerine.
There is no molecule of cellulose, but the formula C24H40O20 describes its composition. It is, of course a carbohydrate, since H and O are in the ratio 2:1, consisting of linked sugar molecules. Sugar is rich in -OH groups. Nitration replaces -OH by -NO3, so if n hydroxyls have been replaced, the formula becomes C24H40-nO20-n(NO3)n. The percentage of nitrogen is easily worked out as N% = 1400n /(648 + 45n). The usual range of n for manufactured cellulose nitrate is 8-12.
Highly nitrated guncotton is insoluble in 2:1 ether-alcohol mixtures, but pyroxyline is completely soluble. Pyroxyline, dissolved in ether, makes films called collodion that were used for early motion picture film. It can be plasticized by a hot mixture of camphor and alcohol. Fillers and pigments can be incorporated, and the mixture hardens as celluloid or xylonite, the first plastic, which filled a long-standing need. It was invented simultaneously in the United States and Britain.
Meanwhile, in 1846, Antonio Sobrero in Milan synthesized glyceryl trinitrate by treating glycerol with concentrated nitric and sulphuric acids. Fortunately for him, he did not synthesize much before discovering that it was a powerful and sensitive explosive, which was named nitroglycerine. This was a much purer and more controllable explosive than guncotton, but it was too sensitive to be generally used, and too powerful for guns. Alfred Nobel, who had become wealthy through the family oil wells in Russia, became fascinated with this powerful explosive and looked for ways to employ it. In 1865, he discovered that nitroglycerine could be detonated by a mercury fulminate primer in a copper tube. The copper cap containing mercury fulminate for detonating gunpowder had been invented in 1816. The next year, he found that nitroglycerine could be rendered insensitive to shock by adsorption in diatomaceous earth, or kieselguhr. 75% nitroglycerine in 25% kieselguhr made an explosive that you could use as a hammer, but would explode with full power when detonated by a fulminate primer. This explosive was called dynamite.
Glyceryl trinitrate is the nitric ester of glycerol, a thick liquid with density 1.6 g/cc, melting at 13°C and becoming rather volatile above 50°C. It invariably explodes at 200°C to 260°C, with a propagation velocity of 7450 m/s. It is difficult to detonate when frozen (below 13°C!). Its vapors cause headache. It is used in small amounts as a medicine to dilate cardiac blood vessels and relieve angina pectoris. The stoichiometric reaction is 4C3H5(ONO2)3 > 12CO2 + 10H2O + 6N2 + O2, which provides 330 kcal/mol, or 1470 kcal/kg. Note that the reaction products are completely gaseous, and that there is excess oxygen, so it produces little smoke. In the diagram, the nitrate group is written ONO2 instead of NO3 to show that O is bonded to the carbon, not N. The NO3's have replaced the OH groups of glycerol.
Guncotton and nitroglycerine are high explosives, which means that they decompose at very high rates, and have a property called brisance, a somewhat foggy concept expressing the shattering power of an explosive. Brisance is a combination of a fast rise of pressure and rapid projection of mass, probably equivalent to the creation of a strong shock front. Black powder is very low in brisance, while guncotton and nitroglycerine are high. In the 1920's and 1930's, liquid nitroglycerine was used for "shooting" oil wells to stimulate production.
Ammonium nitrate, NH4NO3, is also an excellent explosive, used in certain dynamite mixes (Nobel, 1879) and as a nitrate oxidizer in pyrotechnics. It is very hygroscopic and must be protected against moisture. It decomposes to nitrogen and water, giving very little smoke, by the ideal reaction 2NH4NO3 = 2N2 + 4H2O + O2. The excess oxygen can be used to oxidize some organic material mixed with the nitrate, such as wood meal, starch or diesel oil. Explosives of this type have been widely used since 1867. It is rather insensitive, and must be strongly detonated. Its density is 1.725 g/cc. Amatol is a mixture of ammonium nitrate and TNT (see below), either 80:20 or 50:50. The nitrate oxidizes the TNT so that no smoke is produced. It was a popular shell filling, economizing on the expensive TNT and stretching out toluene supplies.
Ammonium nitrate is an excellent nitrogen fertilizer. For this reason, it is readily available in bulk. After World War II, fertilizer-grade ammonium nitrate (FGAN) was shipped in large quantities from Texas to France to aid the recovery of European agriculture. On 16 April 1947, SS Grandchamp blew up at Texas City, followed by the SS Highflyer on the 17 th. On 28 July 1947, SS Ocean Liberty blew up in the harbor of Brest, France. These disastrous explosions demonstrate the power of ammonium nitrate, and led to more careful handling of this cargo.
Permissible or permitted explosives, also called safety explosives, are explosives approved for use in coal mines where there is a hazard of methane explosions. One modern permitted explosive is ANFO, an ammonium nitrate-fuel oil mixture. The idea is to minimize the flame on explosion, and keep it below the temperature that will ignite the methane. These explosives usually contain mainly ammonium nitrate, sensitized with nitroglycerine so they can be exploded with normal detonators (No. 6), and cooling salts, such as sodium nitrate or sodium chloride, or other organic fuel. Low-velocity grades are specially useful for producing lump coal, since they will not shatter the coal as much as the more powerful explosives. It is not a good idea to do blasting in a gassy mine anyway, so it is better to avoid explosions by adequate ventilation than to rely on permissible explosives, which might ignite the methane anyway.
1. J. H. McLain, Pyrotechnics (Philadelphia: Franklin Institute Press, 1980). This is an absolutely excellent and extremely informative book that suffers only from an inadequate index, though references to the literature are extensive.
2. H. Ellern, Modern Pyrotechnics (New York: Chemical Publishing Co., 1961). Another excellent book, with much interesting practical information. Particularly good on spontaneous combustion.
3. H. Brunswig (C. E. Munroe and A. L. Kibler, transl.), Explosives (New York: John Wiley & Sons, 1912).
4. St. H. Brock, A History of Fireworks (London: Harrap, 1947). History of pleasure fireworks by a member of the prominent British fireworks family.
5. J. Bebie, Manual of Explosives, Military Pyrotechnics and Chemical Warfare Agents (Boulder, CO: Paladin Press, 1942). An excellent dictionary of all the terms, trade names, code names and other lore pertaining to explosives.
6. J. Akhavan, The Chemistry of Explosives, (London: The Royal Society of Chemistry, 1998).