Aluminium block bath

Fig. 1. Shallow aluminium block-bath for heating many test-tubes.

Fig. 2. Top surface of deep aluminium block-bath for evaporation to dryness in test-tubes.

It is always indispensable for almost all self-heating chemicals, irrespective of whether they are of the TD type or of the AC type, to determine the or the T, of each run by inserting the reference cell assembly into the adiabatic jacket in the adiabatic self-heating process recorder, or into the aluminium block bath in the isothermal storage testing device, prior to the insertion of the sample cell... 

The cross section of the device is shown in Fig. 119. The aluminium block bath measures 107 mm by 107 mm and 79.6 mm in height. The glass closed cell measures 1.4 cm in outside diameter and about 3 cm in length in other words, it... 

Figure 119. The cross section of the isothermal storage testing device, a. To a temperature recorder b. Thermocouple c. Aluminium lid d. Aluminium block bath e. Glass closed cell f. Sample g. Heater.

Preheating of the aluminium block bath of the isothermal storage testing device and the choice of a nominal T, in the isothermal storage test performed for 0.4 g of collodion cotton confined in the closed cell... 

Insertion of the reference cell assembly into the preheated aluminium block bath in the isothermal storage testing device and the determination of the exact value of TV of the run... 

The reference cell assembly is raised with a pair of fairly large pincers and is inserted carefully down to the bottom of the hole, 23 mm in diameter, 75 mm in depth, bored vertically at the center of the upper surface of the preheated aluminium block bath which is set in the isothermal storage testing device in the meantime, the temperature of the bath is maintained at the T, K of the run throughout every run. 

The exact value of T, of the run is then determined as the arithmetic mean of a series of digital outputs of T, recorded for 2 d prior to the insertion of the sample cell assembly into the aluminium block bath. Fluctuations of the values of T, during this time are within 0.05 K. 

The test, including the heating of the aluminium block bath, is interrupted automatically as soon as the temperature of collodion cotton in the cell increases by 0.3 K (by 0.2 K, as to nitroglycerin) from the T, in order to prevent the cell from exploding. As a matter of fact, however, the test is usually interrupted as soon as the temperature of the high explosive in the cell increases obviously in excess of the T,. ... 

The temperature of the aluminium block bath is set at a proper value, i.e., the nominal T, of the run, by means of the ten-key on the block bath on the basis of the self-healing property of the powdery chemical of the quasi-AC type tested to give estimated values of At of 1 7 d in the isothermal storage test. It is usually a temperature 0" 15 K. lower than the endothermic peak temperature, which is measured by thermal analysis, such as DTA or DSC, of each chemical in the case of powdery chemicals of the quasi-AC type tested herein, with the result that the 7) ranged from 30.08 t for AMVN to 94.0 C for ABCN. As to LPO, the T, ranged from 48.55 to 53.0 C. 

Insertion of the sample cell assembly into the alnminium block bath and the start of the isothermal storage test for 1.2 g of LPO confined in the closed cell and inserted into the aluminium block bath maintained at the T,... 

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