2. Explosive mixtures of the chlorate class. 3. Explosive compounds of the nitro-substitution class. 4. Explosive compounds of the nitric-derivative class. 5. Explosives of the Sprengel class. 6. Fulminates and Amides. 7. Ammunition. Of the seven classifications of explosives, we are dealing with but four in the subject of Bomb Fighting, namely, as classified above, 1, 3, 4 and the Fulminates. =Nitrate Class.= Explosive mixtures of the nitrate class. The best known example of this class is gunpowder, the characteristics of which are that it consists of a mechanical mixture of nitrates with some base containing charcoal or other substance yielding carbon. The nitrates carry the oxygen which combines with the base, under favorable circumstances developing a large volume of gases at a high temperature, so that if the powder is confined at the time of explosion there will be produced an enormous disruptive effect. The standard composition of gunpowder is:-- Potassium Nitrate or Salt-petre 75 parts. Charcoal 15 parts. Sulphur 10 parts. It might be interesting to note that the charcoal employed for military and sporting powder is made from dog-wood, while for inferior grades of powder willow and alder are used. =Explosive Compounds of the Nitro-Substitution Class and Nitric-Derivative Class.= The two explosives of these classes which are generally known are gun-cotton and nitro-glycerine, with special preparations made from them, such as dynamite, blasting gelatine, etc. =Gun-Cotton.= Gun-cotton is made by treating suitably prepared cotton with a mixture of one part by weight of nitric acid and three parts sulphuric acid. The immersion lasts 48 hours, the temperature being maintained at 60 deg. F. The cotton is then subjected to a thorough and prolonged washing, after which it is carried through various processes to prepare it for use. The cellulose of the cotton has thus been converted into tri-nitro cellulose. By varying the strength of the acids different degrees of nitration may be obtained. Gun-cotton is extensively used for military purposes.