Quasi-autocatalytic reaction

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. 

When confined in the closed cell and subjected to the isothermal storage test performed at a T 2 cm of a powdery chemical of the quasi-AC type warms slowly up to the T, but the temperature remains near the T, over a long time, because a phase transition, the endothermic melting, of the chemical occurs almost simultaneously with the exothermic decomposition reaction all through this time. Once, however, the chemical finishes melting in the course of time, an apparently sudden quasi-autocatalytic reaction of the resultant liquefied chemical starts. 

Figure 7. The induction period, of the quasi-autocatalytic reaction, of 2 cin of a powdery clicmical of the quasi-AC type confined in the closed cell and subjected to the isothermal storage test performed at a T, on the high temperature side, recorded for the time. At, from the insertion of the cell into the isothennal storage testing device till the start of the quasi-autocatalytic reaction occurring simultaneously with the finish of melting of the chemical at the T,.

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). 

Nevertheless, however, it is probable, based on the total information obtained above, that tetryl will not start the quasi-autocatalytic reaction at temperatures at which it does not melt. 

It is indispensable also in the isothermal storage test performed for a powdery chemical of the quasi-AC type to confine the chemical in any closed cell, because, once a powdery chemical of the quasi-AC type finishes melting in the cell, the quasi-autocatalytic reaction of the chemical starts, accompanied with the vigorous evolution of some gases including the vaporized chemical itself... 

As to a powdery chemical of the quasi-AC type, there also exists the following fact. That is, as seen in Fig. 7 in Section 3.3, no heat loss occurs at all from the liquefied chemical of the quasi-AC type to the atmosphere at b , i.e., at the time when a powdery chemical of the quasi-AC type starts the quasi-autocatalytic reaction simultaneously with the finish of melting of the chemical, because the condition,... 

Record of the induction period of the quasi-autocatalytic reaction of 1.2 g of LPO confined in the closed cell and subjected to the isothermal storage test performed at the T,... 

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