THE DETONATION PROCESS 89 



the equilibrium constants being taken from data given by Lewis and 

 von Elbe (68). 



The compositions found by Brinkley and Wilson for TNT of density 

 1.46 and by Jones for a slightly different value 1.5 are given in Table 3.2. 

 Jones' results as compared to those of Brinkley and Wilson give larger 

 quantities of CO2 and CH4 at the expense of H2O and CO. The avail- 

 able experimental data of detonation products of course include equi- 

 librium shifts on cooling of the product gases and so are not directly 

 applicable for comparison. They do, however, indicate much smaller 

 quantities of methane, and it is not unreasonable to believe that these 

 may have been formed as a consequence of reactions during the cooling 

 process. The reactions involving CO and CO2 may also be expected to 

 shift, and on the whole it is reasonable to suppose that the compositions 

 obtained by Brinkley and Kirkwood approximate the actual conditions 

 more closely. This is particularly true when the compositions are con- 

 sidered in connection with calculation of detonation properties, as the 

 Brinkley- Wilson method is based in part on such data. As might be 

 expected their results do give much better agreement on detonation rate 

 than do those of Jones. The values are compared in Table 3.3. 



The observed detonation velocity for po = 1.50 is 6,620 m./sec. 

 from Messerly's data (72), and at po = 1.46 interpolation between values 

 gives 6,470 m./sec. in excellent agreement with Brinkley and Wilson. 

 Experimental data for pressures behind the detonation front indicate 

 values of the order of 200 kilobars,^ but are sufficiently inaccurate that 

 they constitute only a qualitative indication. 



Detonation velocities are measured by a number of methods, one of 

 the most elegant employing a camera with a drum rotating at high speed 

 on which is recorded the advance of the luminous detonation front along 

 a stick of explosive initiated at one end. This same general technique 

 has been employed to estimate the detonation pressure by an ingenious 

 method in which the velocity of a shock wave started by the detonation 

 in a lead strip is measured, the pressure being estimated from compres- 

 sibility data for lead. The procedure involves an extrapolation which, 

 together with experimental errors, makes the results only approximate. 

 Shock wave velocities in water can also be measured and can similarly 

 be used to estimate pressures near small charges, an experimental pro- 

 cedure described more fully in Chapter 6. 



3 This value was estimated from experiments made at the Explosives Research 

 Laboratory, Bruceton, Pa., in which the shock wave velocity through a lead sheet 

 in contact with a pentohte slab was measured. The measured velocity was 2,670 

 m./sec, corresponding to a pressure of 140 kilobars on the basis of extrapolated 

 compressibility data. The detonation pressure was estimated to be from 40 to 80 

 kilobars higher, the difference being due to loss of pressure in expansion of the prod- 

 uct gases against the lead. Because of the extrapolation of the pressure-velocity 

 curve for lead and this correction, the figure obtained is only quahtatively reliable. 



