Melting pyrotechnics

Sodium nitrate is also used in formulations of heat-transfer salts for he at-treatment baths for alloys and metals, mbber vulcanization, and petrochemical industries. A mixture of sodium nitrate and potassium nitrate is used to capture solar energy (qv) to transform it into electrical energy. The potential of sodium nitrate in the field of solar salts depends on the commercial development of this process. Other uses of sodium nitrate include water (qv) treatment, ice melting, adhesives (qv), cleaning compounds, pyrotechnics, curing bacons and meats (see Food additives), organics nitration, certain types of pharmaceutical production, refining of some alloys, recovery of lead, and production of uranium. 

A stoicheiometric mixture with sucrose ignites at 159°C, and has been evaluated as a rocket propellant [1], Dry powdered mixtures with glucose containing above 50% of chlorate explode under a hammer-blow [2], Pyrotechnic mixtures with lactose begin to react exothermally at about 200°C, when the lactose melts, and carbon is formed. This is then oxidised by the chlorate at about 340° C. The mechanism was studied by DTA [3],... 

Any gas-producing pyrotechnic compositions must be both hot enough to melt and volatilise the dye and gassy enough to disperse the... 

Differential thermal analysis (DTA) has provided a wealth of information regarding the thermal behavior of pure solids as well as solid mixtures [10]. Melting points, boiling points, transitions from one crystalline form to another, and decomposition temperatures can be obtained for pure materials. Reaction temperatures can be determined for mixtures, such as ignition temperatures for pyrotechnic and explosive compositions. 

Phosphorus is available in two forms, white (or yellow) and red. White phosphorus appears to be molecular, with a formula of P,. It is a waxy solid with a melting point of 44°C, and ignites spontaneously on exposure to air. It must be kept cool and is usually stored under water. It is highly toxic in both the solid and vapor form and causes burns on contact with the skin. Its use in pyrotechnics is limited to incendiary and white smoke compositions. The white smoke consists of the combustion product, primarily phosphoric acid (H 3PO,). 

Several metallic sulfide compounds have been used as fuels in pyrotechnic compositions. Antimony trisulfide, Sb 2S3, is a reasonably low-melting material (m.p. 548°C) with a heat of combustion of approximately 1 kcal/gram. It is easily ignited and can be used to aid in the ignition of more difficult fuels, serving as a "tinder" in the same way that elemental sulfur does. It has been used in the fireworks industry for white fire compositions and has been used in place of sulfur in "flash and sound" mixtures with potassium perchlorate and aluminum. 

TABLE 5.8 Melting and Boiling Points of Common Non-Gaseous Pyrotechnic Productsa... 

Dlphenylamlnochlorarslne (DM) Is a canary-yellow crystalline solid (see Table 4-1). It Is Insoluble In water, but soluble In organic solvents It melts at 195°C and bolls at 410°C.S it was first prepared by Welland in Germany (1915) and independently (1918) by Adams in the United States. During and after World War I, it was known as Adamsite. Slm O described Its odor as that of burning fireworks. DM can be disseminated as an aerosol, either from pyrotechnic mixtures in grenades or bombs, sprayed as a solution, or dispersed as a dust. It has been described as an irritant smoke, a stemutator, and a "sneeze gas."... 

Kosowski, B.M., and Taylor, R.C. (1995) Methods and compositions for melt-cast explosives, propellants and pyrotechnics. US Patent 5,431,756. 

In a nutshell, Mg and Al are the most commonly used pyrotechnic fuels to create heat and light. Both have been used in the development of radiation effect. While Mg is the fuel of choice for most illuminating and tracer formulations, Al is still the main ingredient of photoflash and thermite formulations. The pyrotechnic behavior of Mg is due to its low melting and boiling points in comparison to most... 

Some of the important properties which are considered when choosing the ingredients for pyrotechnic formulations are density, hygroscopicity, melting and boiling points and decomposition temperatures, oxygen content of oxidizers, thermal conductivity of fuels and containers, nature of combustion products and toxicity etc. 

---