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Still air results (enclosed environment)


The start weights of iodine used for the experiments were as follows (assuming 100% conversion of 3I2 to NI3).

Flask number Mass of I2 used (g) No. moles I2 No. moles of NI3 produced Solvent used
1 0.5211 2.0531 x 10-3 6.8437 x 10-4 None
2 0.5102 2.0102 x 10-3 6.7007 x 10-4 Water
3 0.4998 1.9692 x 10-3 6.5640 x 10-4 Pyridine
4 0.5027 1.9806 x 10-3 6.6020 x 10-4 0.880 S.G. NH3
5 0.5225 2.0586 x 10-3 6.8620 x 10-4 2M NH3 (aq)

Sample 3 dissolved on contact. It was impossible therefore re-weigh it.

With the exception of samples 1 and 3, there was no detectable mass change over the period of time used. It is possible to conclude that over a short period of time, NI3 is stable when kept under a non - organic solvent.

Sample 1 had lost 0.0299 g after this period of time and on moving the sample, no explosion had occurred. Examination of the paper did not show any evidence of sample detonation (normally apparent by small pinholes appearing in the paper with brown / purple marks around the edges).

Further contact with the sample caused a small detonation, though not to the same degree as if the sample had been freshly made and used within a few minutes.

A possible reason for the lack of detonation may be that some iodine had sublimed from the surface of the crystal structure with the resultant material having less of an explosive potential. This reason can be verified by the study of other nitrogen containing explosives and detonators. After a period of time, the explosive potential decreases due to break down of the explosive, nitrogen being used by any fungi which may grown on the explosive. This is possible as a large number of commercial explosives contain compounds on which moulds can grow on.

Method Sonic bath

The masses of iodine used for this series of experiments are given in the table below. It is assumed that there is a 100% conversion of 3I2 to NI3.

Flask number Mass of I2 used (g) No. moles I2 No. moles of NI3 produced Solvent used
1 0.5003 1.9712 x 10-3 6.5707 x 10-4 None
2 0.5118 2.0164 x 10-3 5.0410 x 10-4 Water
3 0.5201 2.0492 x 10-3 6.8307 x 10-4 Pyridine
4 0.5031 1.9822 x 10-3 6.6073 x 10-4 0.880 S.G. NH3
5 0.4899 1.9302 x 10-3 6.4340 x 10-4 2M NH3 (aq)

The temperature in all of the flasks at the start of the experiment was 23 C 0.2 C.

Sample number Time for detonation (mm:ss) Final temp of flask Diff. C
1 0.23 23 C 0.2 C 0
2 4.55 23.8 C 0.2 C 0.8
3 0 (see below) 23 C 0.2 C 0
4 9.59 24 C 0.2 C 1
5 6.02 23.9 C 0.2 C 0.9

The NI3 dissolved instantly on contact with the pyridine. This experiment did not yield a decomposition as there was no NI3 to decompose.

Method Direct heating.

The following masses were used for this experiment. It was assumed for a 100% conversion of 3I2 to NI3

Sample number Mass I2 used (g) No. moles I2 No. moles NI3
1 0.5111 2.0137 x 10-3 6.7123 x 10-4
2 0.4988 1.9653 x 10-3 6.5510 x 10-4
3 0.5051 1.9901 x 10-3 6.6337 x 10-4

The experiment was performed three times to ensure consistency of results. The samples detonated at 23 seconds (average) with the temperature at 42 C.

Method Sonic detonation

A sample of 0.5312g I2 (2.0929 x 10-3 moles yielding 6.9763 x 10-4 moles NI3) was used for this experiment. Subsequent experiments used a similar weight, though these were not performed quantitatively. The frequency range went from 1 Hz to 5 kHz.

The first part of the experiment determined the degree of error between the value given on the signal generator dial and that which was recorded using the oscilloscope. The diagram below (diagram 11) shows that this error is very small (there is very little deviation in the line from linearality)

Diagram 11. Error level in the given and true signal frequencies

The major problem with moving the speaker was that any vibrations may detonate the NI3. It was simpler to keep the speaker at a constant distance from the sample and move the sample by the use of lab jacks to the appropriate height. The movement would be far gentler and less likely to detonate the sample.

The NI3 detonated at 1100 Hz after being subjected to this for 4 minutes 57 seconds.

The power output of the speaker was measured using a Blackstar 3225 Multimeter which was connected across the internal electronics of the speaker. This connection was to ensure that the power being measured was the power after amplification. A signal was fed into the speaker. The voltage and current was then measured. The signal was at 1100 Hz.

The power input was also found by measuring the voltage and current directly from the signal generator into the multimeter.

Input readings Speaker readings
Volts 2.05 0.02 Volts 5.70 0.02
Current 25.1 0.3 mA Current 688 0.3 mA
Power (watts) 5.15 x 10-5 Power (watts) 3.92

If it is assumed that the speaker is 1% efficient, that is, the power output is 1% of the post amplified sound, the rest being absorbed back into the speaker or converted to heat energy within the speaker, then the amount of power absorbed by the NI3 can be found.

The distance from the sample to the speaker was 48 cm at 1100 Hz. The diameter of the NI3 as measured across the face of the sample, and not taking into account any dips or troughs for the uneven-ness of the sample surface, (these, to an approximation, will cancel each other out) was 0.5 cm.

To calculate the amount of power incident to that of the NI3, the following calculations are required equations (20) and (21) were used. The result was then multiplied by 60 (to convert the answer into power per minute) and then further multiplied by 5 for the total amount of power to which the sample was subjected.

Not all of the power was absorbed at once by the sample. This was apparent as the sample did not detonate for 5 minutes. It was shown that only 5 % of the power was absorbed by the sample, the rest was reflected. This measurement was performed by placing a microphone at an angle of 45 from the speaker and 0.48 m from the sample. The power of the reflected signal was measured by connecting the microphone directly to a multimeter. Thus the total power the sample was subjected to should be multiplied by 5/100, to give the amount of power which was absorbed by the sample.

The 0.5g samples of NI3 were detonated by the adsorption of 4.56 milli Watts of power over approximately 5 minutes.