Chemistry of pyrotechnics

REQUIREMENTS FOR A GOOD HIGH-ENERGY MIXTURE

The requirements for a commercially-feasible high-energy mixture can be summarized as follows, keeping in mind the preceding discussions of materials and factors that affect performance

1. The composition produces the desired effect and is efficient both in terms of effect /gram and effect /dollar.

2. The composition can easily and safely be manufactured, handled, transported, stored, and used, assuming normal treatment and the expected variations in temperature.

3. Storage lifetime is acceptable, even in humid conditions, and there is reasonably low toxicity associated with both the starting materials and reaction products.

These requirements seem rather simple, but they do restrict or eliminate a number of potential starting materials. These compounds must either be deleted from our "acceptable" list or special precautions must be taken in order to use them. Examples include

Potassium dichromate (K 2Cr2O 7): This is a strong oxidizer, but it only contains 16% oxygen by weight. It has a corrosive effect on the mucous membranes, and its toxicity and suspected carcinogenicity suggest the use of alternate oxidizers.

Ammonium perchlorate (NH,,ClO,,): This is a good oxidizer, and can be used to make excellent propellants and colored flames. However, it is a self-contained oxidizer-fuel system (much like ammonium nitrate). The mixing of NH 4+ (fuel) and C1Oa - (oxidizer) occurs at the ionic level. The potential for an explosion cannot be ignored. Conclusion: if this material is used, it must be treated with respect and minimum quantities of bulk powder should be prepared.

Magnesium metal ( Mg) : This is an excellent fuel and produces brilliant illuminating mixtures. The metal is water-reactive however, suggesting short shelf-life and possible spontaneous ignition if magnesium-containing mixtures become wet. Conclusion: replace magnesium with the more stable aluminum (or possibly titanium) metals. If magnesium gives the best effect, coat the metal with an organic, water-repelling material.