Period of the autocatalytic

The SADT for a high explosive of the true AC type depends on the induction period of the autocatalytic reaction however, the autocatalytic reaction does not depend, in principle, on the quantity of the high explosive. On the other hand, as will be explained hereafter in the present chapter, the SADT for a powdery chemical of the quasi-AC type depends on the phase transition, the melting however, it does also not depend, in principle, on the quantity of the chemical. 

Based on our understanding above referred to, an important and useful proposition is obtained that it is possible, in principle, to regard the SADT calculated in accordance with Eq. (59) holding for the induction period of the autocatalytic reaction, or of the quasi-autocatalytic reaction, of 2 cm of a chemical of the AC type, including every powdery chemical of the quasi-AC type, confined in the closed cell and subjected to the isothermal storage test, as the SADT for the chemical, having an arbitrary shape and an arbitrary size, confined in an arbitrary closed container of the corresponding shape and size, and placed in the atmosphere under isothermal conditions. 

On the other hand, when confined in the closed cell and subjected to the isothermal storage lest performed at a T, on the low temperature side, the time interval up to the start of the quasi-autocatalytic reaction occumng simultaneously with the finish of melting of 2 cm of a powdery chemical of the quasi-AC type becomes naturally far longer, and the temperature decrement caused by melting also becomes of the order of 0,1 0.2 K only. In the meantime, the rate of increase in temperature of the chemical after the start of the quasi-autocatalytic reaction also becomes so slow, as shown in Fig, 16, that it becomes somewhat uncertain to locate the point of time b on the chart of the strip-chart recorder (see Fig. 143 in Subsection 10.2.5, as an example). The same is true of the induction period of the autocatalytic reaction of a high explosive of the tnie AC type (see Fig. 125 in Subsection 9.3.5, as an example). 

In other words, the concept of the SADT is in harmony only with the induction period of the autocatalytic reaction, or of the quasi-autocatalytic reaction, of 2 cm of a chemical of the AC type, including every powdery chemical of the quasi-AC type, confined in the closed cell and subjected to the isothermal storage test. 

Five induction periods, of the autocatalytic reaction, of 0.4 g each of five samples of collodion cotton confined each in the closed cell and subjected each to the isothermal storage test performed at each T, in the range of 72,97 to 94.98 "C with mutual intervals of 2 7 K, recorded each for the time. At, from the insertion of each cell into the isothermal storage testing device till the start of the autocatalytic reaction of collodion cotton at the corresponding T, are presented in Fig. 125, The time axis on the other side in Fig. 125 and that in Fig. 126 are graduated in d to meet the sense of long time, respectively. The points marked with b" on the curves in Fig. 125 correspond to the point of time b ill Fig. 6 in Section 3.1, respectively. 

The individual values of the two coefficients, a and b, of Eq. (59) holding for the individual induction periods of the autocatalytic reaction of 2 cm each of the seven high explosives of the true AC type, other than collodion cotton, confined each in the closed cell and subjected each to the isothermal storage test were also calculated by applying the regression analysis to the individual... 

The characteristic of the self-heating process or behavior of collodion cotton has been described in detail in Subsection 9.3.5, so that only the difference, in the effect of humidity on the induction period of the autocatalytic reaction, between collodion cotton and nitroglycerin is described here. 

The reason why wet nitroglycerin starts the autocatalytic reaction later than dry nitroglycerin at the same temperature is not explainable herein. There may, however, exist some difference, in the mode of the decomposition reaction during the induction period of the autocatalytic reaction of nitrate esters, betw een the liquid water which may be present in wet nitroglycerin at temperatures near 55 °C and the aqueous vapor which may be present in wet collodion cotton at temperatures near 80 X. ... 

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