Pyrotechnic Composition - Materials Used - Oxidizers

Oxidizers

Perchlorates, chlorates and nitrates are the most commonly used oxidizers for flash powders. Other possibilities include permanganates, chromates, and some oxides. Generally, the less the oxidizer, the slower the burning and the more light produced. For use at very high temperatures, sulfates can be used as oxidizers in combination with very strongly reducing fuels.

Oxidizers in use include:

  • Perchlorates (also serving as chlorine donors):
    • Potassium perchlorate – common, relatively stable. Almost non-hygroscopic. Low solubility in water. Produces high temperature flame and smoke of potassium chloride. Safer replacement of potassium chlorate. Impact-sensitive with phosphorus,
    • Ammonium perchlorate – the most common oxidizer for modern solid rocket fuels; more sensitive to mechanical stimuli than potassium perchlorate. Uncommon in fireworks; creates hot flame, enhances barium, strontium and copper colorants by acting as a chlorine donor. Reacts with magnesium when wet and liberates heat and ammonia, can self-ignite. In contact with potassium nitrate (e.g. in black powder) produces potassium perchlorate and hygroscopic ammonium nitrate; no such reaction with sodium nitrate. Reacts with potassium chlorate, producing unstable, gradually decomposing ammonium chlorate; such combination has to be avoided.
    • Nitronium perchlorate
  • Chlorates (also serving as chlorine donors, incompatible with ammonium salts because of forming unstable explosive ammonium chlorate, incompatible with sulfur and other acidic chemicals because of production of spontaneously igniting chlorine dioxide; very dangerous with phosphorus; should not be combined with hydrocarbon fuels/binders, e.g. asphalt or gum arabic; should be replaced with safer perchlorates wherever possible):
    • Potassium chlorate – much less stable than perchlorate, hazardous, avoid if possible. High burning speed, easy ignition. Slightly more hygroscopic than potassium nitrate. Produces smoke of potassium chloride. Can act as a chlorine donor. High impact and friction sensitivity with sulfur and sulfides. With ammonium salts produces unstable ammonium chlorate. Used in match head compositions, some colored smokes, and small firecrackers and toy caps.
    • Barium chlorate – also serves as a green colorant in fireworks; sensitive, better to avoid. Almost non-hygroscopic. Compositions may spontaneously combust in sunlight. Very good green colorant, even in lower-temperature flames.
    • Sodium chlorate – much less stable than perchlorate, hazardous, also serves as yellow colorant, hygroscopic
  • Nitrates (when mixing with aluminium, boric acid should be added as a stabilizer):
    • Potassium nitrate – very common, used in black powder and wide variety of compositions. Not very hygroscopic. At lower temperatures (with ordinary fuels like rosin or shellac) not very efficient, does not burn well, produces potassium nitrite. At higher temperatures, with charcoal and sulfur or with magnesium, decomposes well. Does not produce sufficient temperature to make colored flames, except when magnesium is added. Makes good sparks. Presence in dust makes the dust hazardous and very flammable.
    • Sodium nitrate – also a yellow colorant, hygroscopic. Gives intense yellow light, used for illumination compositions. Presence in dust makes the dust hazardous. At lower temperatures produces nitrite ash, at higher temperatures decomposes completely.
    • Calcium nitrate – also a red-orange colorant, enhances other colors
    • Ammonium nitrate – used in some less common composite rocket propellants, hygroscopic, decomposes at too low temperature; when dry reacts with Al, Zn, Pb, Sb, Bi, Ni, Cu, Ag, Cd; when wet reacts also with Fe. Forms an explosive compound with copper.
    • Barium nitrate – most common oxidizer/colorant for green and white colors, but with somewhat weak colorant effect;requires a chlorine donor. Also used in flash powders and some military infrared flares. Barium also serves as a stabilizer for the mixtures; decomposes at higher temperatures than nitrates of lighter metals and promotes higher burning temperatures. With aluminium produces bright silver sparks; when used with aluminium, addition of boric acid as stabilizer is advised. Not very hygroscopic.
    • Strontium nitrate – most common oxidizer/colorant for red colors in flares, fires, and stars; strontium also serves as a stabilizer for the mixtures. At lower temperatures (with organic fuels) produces strontium nitrite ash which can smother the flame; decomposes completely at higher temperatures (with magnesium). Colorant for low-temperature flames, colorant and oxidizer for hot flames.
    • Caesium nitrate – used in some military infrared flare compositions
  • Permanganates:
    • Potassium permanganate – used in early mixtures, now considered to be sensitive and unstable
    • Ammonium permanganate – a moderately powerful explosive
  • Chromates:
    • Barium chromate – used in delay compositions, e.g. in fireworks rockets
    • Lead chromate – used in delay compositions
    • Potassium dichromate – used infrequently as an oxidizer; can be used as a surface treatment for passivation of magnesium particles, also as a catalyst and in some matches; potassium perchlorate often added
  • Oxides and peroxides:
    • Barium peroxide – unstable, spontaneously decomposes, compositions containing it should not be stored
    • Strontium peroxide
    • Lead tetroxide – versatile but toxic
    • Lead dioxide – used in friction-sensitive compositions, e.g. matches
    • Bismuth trioxide – used as a safe alternative to lead tetroxide in some compositions
    • Iron(III) oxide – a high temperature oxidizer, a catalyst
    • Iron(II,III) oxide – an oxidizer in Thermite and Thermate
    • Manganese(IV) oxide – an oxidizer in manganese thermite, a catalyst
    • Chromium(III) oxide – an oxidizer in chromium thermite
    • Tin(IV) oxide – an oxidizer in some delay charges
  • Sulfates (reactions require high temperatures and strongly reducing fuels):
    • Barium sulfate – a high-temperature oxidizer for e.g. strobe compositions, a green colorant
    • Calcium sulfate – a high-temperature oxidizer for e.g. strobe compositions, a red-orange colorant; calcium salts used to deepen fireworks colors
    • Potassium sulfate – a high-temperature oxidizer, a purple colorant
    • Sodium sulfate – a high-temperature oxidizer, a yellow colorant
    • Strontium sulfate – a high-temperature oxidizer, a red colorant
  • Organic chemicals
    • Guanidine nitrate – used in some high power rocket fuels, propellants, and blue firework compositions
    • Hexanitroethane – used in some special military compositions
    • Cyclotrimethylene trinitramine – used in some double-base propellants
    • Cyclotetramethylene Tetranitramine – used in some double-base propellants
  • Others
    • Sulfur – oxidizer for zinc in zinc-sulfur fuels
    • Teflon – oxidizer for some metal fuels
    • Boron – oxidizer for titanium, forming titanium diboride

Corresponding sodium salts can be substituted for potassium ones.

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