Factors affecting sensitivity measurements

In this chapter we will briefly survey some of the most commonly used measures of sensitivity, as well as some earlier correlations between sensitivity and molecular properties. This will provide a basis for further discussion of factors affecting sensitivities and the subsequent presentation of correlations developed in our laboratory. It is often the exceptions to structure-sensitivity relationships that offer the greatest promise in broadening our understanding of the reactivities of energetic compounds. Studies of several exceptional systems will be presented and discussed in the light of unique structural or reactive features which can account for their observed behavior. 

Dunkle s Syllabus (1957-1958) Shock Tube Studies in Detonation (pp 123-25) Determination of Pressure Effect (144-45) Geometrical and Mechanical Influences (145-48) Statistical Effects of Sensitivity Discussion on Impact Sensitivity Evaluation (148-49) Pressure in the Detonation Head (175) Temperature of Detonation (176) Charge Density, Porosity, and Granulation (Factors Affecting the Detonation Process) (212-16) Heats of Explosion and Detonation (243-46) Pressures of Detonation (262-63) A brief description of Trauzl Block Test, Sand Test, Plate Dent Test, Fragmentation Test, Hess Test (Lead Block Crushing Test), Kast Test (Copper Cylinder Compression Test), Quinan. Test and Hop-kinson Pressure Bar Test (264-67) Detonation Calorimeters (277-78) Measurements... 

Several forms of the superoxide 02 radical ion formed on the surface of ZnO, MgO, CoO/MgO and Si02 have been reported in [40, 83]. The species were differed by the orientation of the 0-0 residue relatively the surface and the metal ion Mn+. The correlation between distances and angles in the most probable structures with the experimentally measured gz values was found, and the dynamic behaviour observed in some cases was also discussed [83], Calculated EPR spectra of the adsorbed 02 for different charges of the metal ion Mn+ (2 < n < 6) showed that gz values are sensitive to the ionic charge and the increase of n+ causes the decrease of gz [83]. The z-axis of the tensor is usually in the direction of the internuclear axis and the x- direction is that of the mole-cular orbital hosting the unpaired electron. The data in Table 8.3 show that the dependen-ce of gz on n+ is, however, valid quantitatively not always because of rather many factors affecting the gz value (distances to the neighbouring atoms, orientation, local fields, etc.). Additional detailed information can be found in references cited in this section. 

Fluorescence is generally more sensitive to environmental factors than absorbance measurements. Signal intensity may be affected by pH, temperature, quenching, interfering substances, solvent, or interference from Rayleigh and Raman scattering. Many fluorescent species contain ionisable groups whose fluorescent properties are sensitive to pH. In some cases only one of the ionised species may be fluorescent. An example is the barbiturates which only fluoresce at elevated pH in the di-anionic form. The relationship of fluorescence intensity with pH should always be examined as part of the development of the method. 

Chapters 4-6 deal explicitly with the standard "sensitivity" tests and with some of the recent attempts to improve them. Other discussions in the chapters try to understand the function of the tests, interpret their meaning, and detail the material and other factors known to affect the measures of sensitivity. 

The nonreproducibility of data implies that the tests and the meaning of the term "sensitivity" need further study and understanding [6]. Questions arise as to whether certain tests actually measure the effect of the specified stimulus, even as one among several stimuli directed at the test sample by the apparatus. Kistiakowsky and Connor [1] concluded that a definite mechanical sensitivity of an explosive was not found. Koenen et al. [2] and Afanas ev and Bobolev [5] also concluded that an intrinsic impact sensitivity of an explosive does not exist, but is a function of the test method, container, compression, arrangement of the sample, state of the sample tested, its method of preparation, particle size and shape, and possibly the climactic conditions during testing. By extension these factors can also be expected to affect sensitivities to other stimuli. 

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