Dynamites

secondary explosives that contain a significant amount of liquid nitric esters. The main component of dynamites is nitroglycerin, usually mixed with nitroglycol or diethylene glycol dinitrate to lower the solidification temperature. Dynamites are classified as mixed or gelatine, depending on their composition, and as high-percentage or low-percentage, depending on the amount of nitroglycerin.

Mixed dynamites consist of nitric ester and a powdered porous absorbing agent. For example, high-percentage mixed dynamite, or Guhr II dynamite, is a mixture consisting of 25 percent kieselguhr and 75 percent nitroglycerin (by weight). This moist, friable substance is similar to oily chernozem. Low-percentage mixed dynamites, called detonity (a mixture of nitroglycerin with diethylene glycol dinitrate [6-15 percent], ammonium nitrate, trinitrotoluene, and aluminum powder), are widely used in the USSR. Detonit is a friable powder with a density of 1.0-1.3 g/cm³ and a heat of explosion of 5,030-5,870 kilojoules per kg (kJ/kg), or 1,200-1,400 kilocalories per kg (kcal/kg).

Gelatin dynamites are plastic, high-density mixtures based on gelatinized nitric esters. The esters are produced by introducing pyroxylin (not more than 10 percent) into the nitric ester. In particular, nitroglycerin gelatinized by 7-10 percent pyroxylin is called blasting gelatin. This elastic semitransparent substance is one of the most powerful explosives: heat of explosion, 6,500 kJ/kg (1,550 kcal/kg); rate of detonation, 8 km/sec; density, 1.6 g/cm³. Gelatin dynamites can vary in composition. For example, high-percentage gelatin dynamite has 62 percent liquid nitric esters, 3.5 percent pyroxylin, 2.5 percent sawdust, and 32 percent sodium and potassium nitrates (by weight); density, 1.4-1.5 g/cm³; heat of explosion, 5,450 kJ/kg (1,300 kcal/kg). The main shortcomings of gelatin dynamites are a decrease in detonating capacity when stored (so-called aging) and freezing of the mixture of nitric esters at temperatures below -20°C.

Dynamites are prepared by mixing the components in mechanical mixers. The product is then placed in paper cylinders (cartridges) 2-3 cm in diameter and about 10 cm long. In the late 19th and first half of the 20th century, dynamites were the main type of industrial explosive. Attempts were also made to use them in military affairs. High cost and danger of handling led to the replacement of dynamites by ammonites, dynammons, and water-filled explosives. However, there is still considerable production of dynamites in a number of countries. They are used mainly in the mining industry in underground workings in hard rock, where high potency and detonating ability are required. Dynamites are used to a limited extent in the USSR for blasting operations in very hard, tough rock that is abundant in water (in mines where there is no danger from gas or dust).