GUNPOWDER 763 



pears, however, that an Arabic manuscript exists in the collection of thoEscurial which 

 unmistakeably describes gunpowder and its properties, the date of which is anterior 

 to 1250. Mallet. 



This-well known composition is employed for charging the numerous varieties of 

 fire-arms. Its use depends upon the fact that, at the moment of ignition, violent 

 deflagration takes place, accompanied by the evolution of a large volume of gas. It is 

 evident that if the explosion occurs in a limited space, a vast pressure accumulates and 

 becomes a propulsive force. The gas produced by the explosion of good gunpowder 

 occupies .nearly 900 times the volume of the powder itself; but, owing to the high 

 temperature, the space occupied by the gas at the moment of formation is probably 

 nearly 2,700 times greater than the volume of the powder. One of the most popular 

 errors regarding the projectile force of explosive substances arises from the extremely 

 vague meaning generally attached to the words strong, powerful, and other equivalent 

 terms. It is this which leads so many to imagine the possibility of attaining 

 marvellously long ranges by means of the various fulminating substances known 

 to chemists. The latter are unfit for use in fire-arms, owing to a variety of circum- 

 stances. One of them is the extreme rapidity of their explosion. The whole mass ap- 

 pears to be converted into gas at once, whereas in gunpowder the ignition proceeds from 

 particle to particle. The action of fulminates is also too local ; if a portion of any of 

 the more violently explosive substances be fired on a piece of metal, the latter will bo 

 perforated or depressed exactly at the spot occupied by the substance, and if it be 

 attempted to use it to charge fire-arms, they will be destroyed, and yet, in all proba- 

 bility the bullet not projected. Moreover, it is impossible to use fulminates success- 

 fully for charging shells, because the latter, instead of being blown into pieces of 

 moderate size, capable of inflicting large wounds and throwing down buildings, 

 become converted into fragments so small as to be far less destructive. 



It has been found that no composition fulfils so many requisites for charging fire- 

 arms as a mixture, in due proportions, of sulphur, nitre, and charcoal. It is this 

 composition which, in the form of small grains, more or less polished, constitutes 

 gunpowder. The latter should possess several properties which, although sometimes 

 tending in opposite directions, are not entirely incompatible, and may therefore be 

 nearly attained in practice. Some of the principal of these are the following : 

 1. The proportions should be so adjusted that the combustion may be complete, and 

 little residue be left after explosion. 2. The powder should be as little hygrometric 

 as possible. 3. It should be sufficiently, but not too explosive. 4. It should be hard 

 and dense enough to bear carriage without breakage of the grains. 



Too great a proportion of carbon and sulphur will cause rapid fouling of the gun, 

 and the explosive force will be less than it should be ; too small a proportion of 

 sulphur will render the powder too hygrometric. The presence of soda Or chloride of 

 potassium in the nitre will lead to the same fault. The powder must be sufficiently 

 stamped, or it will not possess the fourth requisite. 



The history of gunpowder may be conveniently studied under the following 

 heads : 



Preparation of the ingredients. 



Mixture and granulation. 



Modes of estimating projectile force. 



Analysis of gunpowder. 



PBEPAEATION or THE INGBEDEBNTS. 



Preparation of the Nitre. The nitre employed for powder is always in a state of 

 almost absolute purity, especially as regards the presence of the chlorides of potassium 

 or sodium. The crude nitre of commerce contains several impurities, among which 

 are found nitrates of soda and lime, chlorides of potassium and sodium, and sulphates 

 of potash and soda. They are all removed by crystallisation. The principal impurity 

 is common salt. The process of purification is founded on the fact, that the latter 

 substance is almost equally soluble in hot or cold water, whereas nitre is far more 

 soluble in hot than in cold water. The following is the French mode of refining 

 saltpetre : 1,200 kilogrammes are gently heated with 600 litres of water in a copper 

 boiler. The solution is constantly stirred and skimmed, and more nitre is added, 

 until the total quantity is 3,000 kilogrammes. As soon as the whole is added, and it 

 is presumed that all the nitre is dissolved, the common salt is removed from the 

 bottom of the boiler. The solution is now to be clarified with glue. For this pur- 

 pose 400 litres of water are added by small portions, and then 1 kilogramme of the 

 glue dissolved in hot water. The scum, which soon rises, is removed, and the fluid is 

 boiled until clear. The whole is then allowed to cool to about 194, and the solution 

 of nitre is carefully decanted from the layer of common salt into the crystallising 



