It was shown by Kamlet and Jacobs that an explosive's detonation velocity D and detonation pressure P-D are governed largely by (a) the loading density of the explosive, and (b) a factor phi that depends upon the number and masses of gaseous detonation products and the accompanying heat release. For a series of different explosives, we show that the density and phi are both important in determining D and P-D. For a given explosive, however,. is approximately constant and so D and P-D correlate quite well with the density, as has long been known. We propose that phi be interpreted as a measure of the intrinsic detonation potential of an explosive, that is independent of the external factors that affect the loading density. Comparison of phi values for different explosives can provide useful insights into features that promote high detonation velocities and detonation pressures. The parameter phi is related to a property introduced earlier, explosive power, but phi takes into account the fact that part of the carbon content of an explosive typically remains as a residue after the detonation process.