s;eptu.mbeh 33, 1880.] 



FOREST AND STREAM. 



145 



tlien, may furnish oxygen to the combustible just as 

 readily aa the molecules of the atmosphere do, and in a 

 more couceutrated form. Hence, by placing tlie oxygen 

 containing substances with the combustibles we may 

 shut them in from the air, and by sufficiently stimulating 

 their molecularenergy, by the application of heat, producfe 

 combustion. 



Cfimpowder.— loiter or saltpeter is a substance rich in 

 oxygen. Charcoal or carbon is a combustible. Now, if 

 niter be brought into contact with charcoal and some 

 sulphur be added to facilitate ignition, we hare all the 

 non^itions necessary to combustion. This is the common 

 Kunpowder. If, now, a certain quantity of this 

 iirid be confined, as in a gun, away from the air, 

 .3 nited, the result will be a combustion. The oxygen 

 which is stored in the niter is so concentrated that it al- 

 lows a very rapid combustion. This is termed an explo- 



o-glyeerine.—ln place of the charcoal, another 

 Liatible substance, glycerine, may be employed, and 

 instead of the niter, nitric-acid may be used to secure the 

 reqaisite supply of oxygen. This is the compound known 

 as nicro-glycerine. If a mass of nitro-glycerine be con- 

 fined and ignited the result will also be an explosion. 



Now, how shall we explain the tremendous difference 

 of the two explosives? In each compound we have 

 simply combined the conditions necessary to combustion, 

 and the result in each case is simply the production, by 

 a chemical reaction, of a large volume of gas and the 

 consequent liberation of molecular energy in the gas. 

 What is the difference ? 



Simply this : Wliereas, in the gunpowder the union is 

 of the atoms of diil'erent molecules ; in the nitro-glycer- 

 ine it is of atoms within the same molecule. Before the 

 atoms) of the gunpowder oxygen molecules and niter 

 molecules can unite, they must each pass out from their 

 molecules ; in nitro-glycerine they are already in the 

 Bame molecule. 



Explosion of fifMH^ozuder,— Letus goback. Gunpowder 

 ia manufactured by mechanical processes. The charcoal, 

 sulphm- and niter are each ground into dust and then 

 intimately mixed. But by no mechanical treatment can 

 the molecules of the sulphur, niter and charcoal be 

 changed into molecules of any other substance, and 

 hence in the mass of gunpowder, which consists of 

 grains, each individual grain is made up of countless 

 molecules of sulphur, niter and carbon. The generation 

 of gases can be produced only by the union of the atoms 

 of one molecule with the atoms of other molecules, and 

 tlie process of combustion beginning at one side of one 

 molecule of one grain must extend first through this 

 molecule to the next, and so on to the center of the gr.'iin, 

 and thrnugh to the other side, then to and through the 

 next grain, and so on through all the grains to the ctn- 

 ter of the mass and then through to the other side. The 

 process is one requiring a certain definite interval of 

 time. The generation of gas being progressive the pres- 

 sure must also be cumulative. 



Explosion of Nitroglycet-ine.—Begianing with the 

 manufacture, we find a radical difl'erence between the 

 mixture of the ingredients of gunpowder and the union 

 of the ingredients of nitro-glyceiine. The first was a 

 mechLmical itiixtiire ; the second is a chemical reaction.. 

 The atoms of the nitric-acid molecule unite with the. 

 atoms of llie glycerine molecules and form new mole- 

 cules, which are different substances from the old. 

 Hence, nitro-glycerine is not nitric-acid and glycerine ; it 

 is nitro-glycerine. 



Again, it has been demonstrated by chemical analysis 

 tliat eaeh molecule of this new substance, nitro-glycerine, 

 contains, \yrapped up within itself, the different atoms, 

 which, under the conditions of explosives, may combine 

 witii each other to form new molecules of gas. Hence. 

 in an explosion of nitro-glycerine, it is not necessary for 

 the atoms of one molecule to be set free from that mole- 

 eiile, and to pass out from it to the atoms of other niole- 

 euits. The element of time is thus eliminated, and the 

 process is instantaneous. The conditions which will ex- 

 plode one molecule of nitro-glycerine are sufacient to ex- 

 plode the millions of millions of molecules of the entire 

 mass. The explosion of every part of the entire mass is 

 then simultaneous. This ia termed detonation, 



The different exhibitions of force by slow and quick 

 explosions are too familiar to need rehearsal here. Our 

 study of the subject thu.s far enables ns to understand 

 the piineiples underlying these different effects. 



The moleeules of gas move in straight lines in all di- 



reeriniii-. Tims, when a solid or hquid substance is 



cuhvi'MimA into gas, the pressure of the gas must be ex- 



eii.ii in every direction at once. If an interval of time 



I 1 1 lowed, this pressure concentrates itself in the 



I t least resistance. If no interval of time be al- 



Ij .,1, it cannot so concentrate itself, but must be 



eveiy where alike on every part of tlie surface of the con- 



iMniing body. The difference between the two explosions 



■'< the dilTerenee between a push and a blow. The 



uie of gas, in tlie ime ease, is like a leaden bullet 



I ^11 from tlie hand against a board and rebounding ; 



in the other caae it becomes the same leaden bullet driven 



•with frightful velocity from the muzzle of a gun through 



the board. 



In the discharge of a flre-arm, the pressure of the vol- 

 ume of gas generated by the slow form of explosion in- 

 creases in force and exerts itself in every direction 

 against the surfaces of the gun-chamber and the ball, 

 until it attains a degree of strength sufficient to overcome 

 the resistance of the ball. At that pomt the ball yields, 

 and the pressure at once concentrates itself in the line of 

 this yielding. 



On the other hand, the generation of gas, in the explo- 

 sion of a charge of nitro-glycerine in a gun-chamber, 

 would be instantaneous throughout the whole charge. 

 It would exert itself in every direction at once, and 

 there would be no yielding of the least resistant body to 

 admit of the pressure concentrating itself in the line of 

 least resistance. For to yield requires motion ; motion 

 requires time ; but there is no time ; consequently, no 

 motion. The ball, it is true, would be blown out of the 

 gun, but not before every side of the cliamber alike hatl 

 received the same blow, by which also would the gun be 

 shattered.* 



n, 



THE OBDEES OF EXPLOSIVES, 

 An explosive compound we have seen to be a mixture 

 of substances capable of rapid conversion into gases by 

 the operation of heat. 



An explosion may be defined as "a chemical reaction 

 causing the sudden or extremely rapid formation of a 

 very great volume of highlj-^ expanded gas." 



The effect of the ex])losion, we have also learned, de- 

 jjends upon the rapidity with which it is generated. Meas- 

 ured by this effect, explosives are now divided into two 

 genera,l orders, the first and the second— quick and slow, 

 high and low. It will be more convenient for us to first 

 consider 



EXPLOSIVES OF THE SECOND OBDEE. 



1. In an explosive of the second order the explosion, 

 or freeing of the gases, ia brought about by simple igni- 

 tion. 



3. The process is gradual, from one side of the molecule 

 tlu-ough to the other, from one side of the grain through 

 to the other, and from one side of the mass to the 

 other. 



3. Tills requires time. 



4. Up to a certain point the explosive force grows more 

 powerful as the explosion progresses ; it is cumulative. 



Ti. It concentrates itself in the line of the least resist- 

 ance, and is never greater upon any other part of the 

 containing body than upon the part which yields ; i.e., 

 "it can never be greater than the resistance of the least 

 resistant part." 



6. Confined in a gun this class of explosives are pro- 

 jectile, or ballistic ; they are therefore adapted for use 

 in ordnance and fire-arms. 



7. The distinctive t3'pe of this class is gunpowder. 



EXPLOSIVES OP THE FIRST ORDER. 



1. In an explosive of the first order the explosion, or 

 freeing of the gases, is by detonation. 

 3. It is en masse. 



3. It is instantaneous. A ton explodes just as quickly 

 as an ounce. 



4. It is not cumulative. 



•5. The force is exerted upon every part of the contain- 

 ing body alike. 



6. It is shattering ; and therefore explosives of the first 

 order carmot be used in guns. The smallest charge 

 would burst the gun, 



7. The distinctive type of this class is nitro-glycerine. 



III. 

 DETONATION. 



Before going further we must consider more fully the 

 mechanical nature of the form of explosion called deto- 

 nation. 



Detonation is the instantaneous conversion of the 

 whole ma-ss of a body into gas. Those who liave studied 

 it the most tlioroughly, in theory and by experiment, 

 as exhibited by the typical detonating explosive, nitro- 

 glycerine and its compounds, have determined that ; — 



1. Three agencies combine to produce the action, 

 namely, heat, pressure and motion, the last being either 

 shock, jar or vibration. No one of these alone will pro- 

 duce detonation. 



3. Heat aloue will not produce detonation, A match 

 will ignite unconflned nitro-glycerine, but the liquid 

 ceases to burn when the heat of the match is removed. 

 Nitro-glycerine may be burned with a wick the same as 

 whale oil ; a rag saturated with it burns slowly. Thrown 

 upon the fire or upon a redhot btove, it burns but does 

 not explode. 



3. Simple pressure alone will not produce detonation. 

 This ia sViowii by the fact that the liquid may be stored 

 m such a shape that the pressure of the mass upon the 

 layers next to the bottom must be immense, yet no ex- 

 plosion is caused thereby, 



4. Motion (vibration or jar) does not produce detona- 

 tion. When the nitro-glycerine is spread out on an an- 



♦For an elueidntion of the foregoing subject the reader Is refer- 

 red to Prof. J. P. Cooke's "The New Chemistry" (Applt-ton iCo. 

 33). This folumecontaiaetheuiost admirable eyjitorae of thKsei 

 enoe of chemistry that we have ever seen. We have not hesitaK d 

 to make use of Prof. Cooke's iJlustraiions and in si, me eases of h s 

 languu8e,aud we here malte a geneial aglcuowledgement to him. 



vil and struck with a hammer, although the whole sur- 

 face is jarred thereby, only that portion of It which is 

 between the face of the hammer and the face of the an- 

 vil wiU explode. 



5. Again, the pressure of a greater degree of any one 

 of these three agencies admits of a less proportion of the 

 other two. Thus the greater the degree of heat the less 

 may be the pressure and jar ; the greater the pressure the 

 less the heat and jar ; the greater the jar the leas the heat 

 and pressure. 



Now let us consider the conditions of the detonation of 

 nitro-glycerine and its compounds when confined, for in- 

 stance, in a borehole. Just here we must keep in mind 

 that confinement is not pressure, although it may be an 

 aid to secure pressure. 



6. If a mass of nitro-glycerine be closely confined in a 

 bore-hole, and be simply ignited at one end, the expansion 

 of the volume of gases formed by the combustion of a part 

 of the charge, creates pressure upon the remainder of 

 the mass, until, at a certain point, this pressure becomes 

 powerful enough, in conjunction with the attendant heat 

 and jar, to detonate the rest of the charge. This is a 

 partial detonation of the charge. The action is best 

 shown by an experiment with dynamite, which is a com- 

 bination of nitro-glycerine with a solid substance : A 

 charge of dynamite closely confined in a gas-pipe and 

 simply ignited at one end, will burn through a certain 

 length of the charge, and the rest will, by the pressure, 

 heat and jar, be detonated. The interior of the tube 

 thus burst will be marked so plainly by the two processes 

 that it is possible to determine just where simple combus- 

 tion ended and detonation began. It will be readily un- 

 derstood that the greater the pressure by the confining 

 body the less ignition is necessary, and vice versa. 



7. Again, when the confinement, and consequently the 

 pressure, is less, the detonation may be produced by giv- 

 ing the charge a greater shock. This may be done by 

 means of a strong percussion cap. In the present prttc- 

 tice with high explosives the method of confinement and 

 ignition is not employed ; the approved mode is that of 

 Nobel's invention, the use of a strong cap. 



A clear understanding of these different conditions of 

 detonation will enable us to intelligently study a third 

 order of explosive compounds. 

 IV. 

 EXPLOSIVES OF A TWO-FOLD CONSTITUTION, 



These partake of the nature of low explosives and also 

 of the nature of high explosives ; that is to say, accord- 

 ing to the .adjustment of the conditions of their explo- 

 sion, they may be exploded either by ignition, gi-adually ; 

 or by detonation, en masse i or parlially by ignition and 

 partially by detonation. To this class belong the nitro- 

 cellulose combinations; i. e., the combinations of nitric- 

 acid and celltdose. Cellulose is the vegetable fiber of 

 wood, cotton, etc. — the skeleton of vegetation. 



The prominent type of this class of explosives is 



Gt/N-COTTON. 



1. Gun-cotton is the fiber of cotton treated with nitric- 

 acid. 



!. It is, as an explosive agent, analagous to gunpowder 

 in that it is a porous solid ; is when dry highly in flammable, 

 antl when ignited without confinement it burns like gun- 

 powder by ignition. 



3. It is, as an explosive, analagous to nitro-glycerine. 

 It is made in essentially the same way, hy a chemical 

 reaction, the principal difference being that the nitro- 

 ceUulose, a porous solid, is not so sensitive as the nitro- 



;lycerine, a solid. 



4. This is a ilifferenm of degvee only, not of hind. 



5. It is a difference wlueh may be easily removed by 

 mechanical means, i. e., by bringing the molecules of 

 the mass into closer contact. 



6. This may be done by pressure. 



7. Under pressure gun cotton is analagous to nitro- 

 glycerine in its explosion. It detonates. 



8. The explosion of gun-cotton ignited unconflned is 

 analagous to that of gunpowder ; confined, to that of 

 nitro-glycerine. 



It took along time for men to learn this. The history 

 of the use of the material is curious ; for us it is also in- 

 structive. 



First manufactured in 1888, it was, as its name implies, 

 thought to be a suitable material to supply the place of 

 black powder as a projectile explosive. It was employed 

 in ordnance and in fire-arms. Sometimes It went all 

 right. Sometimes it went all wrong ; exploded with ter- 

 rhfic power, burst the cannon, shattered the ftre-armsy 

 blew men's thumbs off. The manufacturers claimed that 

 they could make it uniform. For all that wo know to 

 the contrary they sent for some of the cotton, contended 

 that it must iiave been the manufacture of the old com- 

 pany, that it did not have the seal of the new company 

 on the tops of the caus : and tlien— in due form, as in 

 such cases made and provided — proclaimed in the papers 

 that their pressure gauge at Bigtown proved conclu- 

 sively not only that this cotton was weaker than that of 

 their own make, but also that the_ fault must have been 

 wholly with the thumbs. But, at all events, the gun 

 cotton burst the guns and blew off the thumbs. 



After Nobel's invention of the method of detonating 



