In the manufacture of gunpowder all that is absolutely necessary is to mix the three ingredients thoroughly and in the proper proportions. But to fit the powder for use in firing small arms and cannon it is made into grains of various sizes, the small sizes being used for the small arms with short barrels, and the large sizes for cannon. The reason for this is that if the powder is made in very small grains it all burns at once, and the explosion takes place so suddenly that an exceedingly strong gun is required to withstand the explosion, while if larger grains are employed the burning is slower and continues until the projectile has traveled to the muzzle of the gun. In this way the projectile is fired from the gun with as much force as if the explosion had taken place at once, but there is less strain on the gun. What Causes the Smoke When a Gun Goes Off? Powder of this latter kind always produces a considerable quantity of smoke when it is fired, because there is a quantity of fine particles formed from the breaking up of the saltpeter and from some of the charcoal which is not completely burned. This smoke forms a cloud that takes some time to clear away, which is a very objectionable feature. In order to get rid of it, efforts were made to produce a substance that would explode without leaving any solid residue, and that could be used in guns. These efforts were finally successful, and there are now several brands of smokeless powder in use. What is Smokeless Powder Made Of? The most satisfactory forms of smokeless powder are all made from guncotton or nitrocellulose. This substance, which is made by treating cotton with a mixture of nitric and sulphuric acids, is a chemical compound, not a mixture like gunpowder; and when it is exploded it is all converted into gases, of which the chief ones are carbonic acid gas, nitrogen, and water-vapor. To cause the explosion of guncotton it is not necessary to burn it, but a mere shock or jar will cause it to decompose with explosive violence. Of course, such a violent explosive as this could not be used either in small arms or in cannon, but guncotton can be converted into less explosive forms which are suitable for use in guns, and the majority, of smokeless powders are made in this way. The methods used in producing the smokeless powders are kept secret by the various countries that use them. What is Nitroglycerine?