34 MODERN SCIENCE READER 



gunpowders, and perhaps the easiest way of showing the 

 striking difference between the old gunpowders and some 

 of the modern propellants is to give you two tables 1 exhibit- 

 ing, first, the volume of gas generated by the explosion; 

 second, the units of heat generated ; and third, the product 

 of the units of heat and volumes of gas, which represents 

 approximately the comparative potential energy of the 

 explosives. 



For cordite, the first modern propellant adopted in Eng- 

 land, we were indebted to the labors of the late Sir F. Abel 

 and Sir James Dewar, and the value of the propellant is 

 sufficiently shown by the fact that with the same maxi- 

 mum pressure artillerists have been able to more than 

 double the energy of the projectile. 



It will be observed that the figures I give as representing 

 the comparative energies of the old propellants vary from 

 200,438 to 179,478, while the similar figures for the modern 

 explosives vary from 1,090,873 to 851,212, or more than 

 four times as great, and the diagram I also show exhibits 

 the comparative pressures developed up to the density of 

 5, thus at the density of 5 the pressure of gunpowder is 

 about 1,700 atmospheres amide powder 3,500 atmos- 

 phereswhile the modern explosives at the same density 

 lie between pressures of 8,600 and 7,200 atmospheres. 



Turning now to the total volumes of gas generated and 

 the units of heat developed by the explosion, I find in the 

 various explosions I have examined the same general rules 

 hold. With the increase of density the volumes of gas 

 decrease and the units of heat increase. 



Now, I have pointed out that with the increase of density 

 there is in all cases a decrease, in most cases a considerable 

 decrease in the volume of gas, and as the pressures devel- 

 oped increase much more rapidly than the density, it is 

 obvious that with increase of density there must be a very 

 considerable increase of temperature. 



At a density of 0.5 I place the temperatures of the high 

 J See original publication if detailed information is desired. 



