Signal Compound

a pyrotechnic compound in a cartridge, flare, rocket or similar device used to produce a flare or smoke signal that can be observed over distances of several kilometers.

Compounds for signal flares contain 60–70 percent oxidizer—usually sodium nitrate (yellow flame), strontium nitrate (red flame), or barium nitrate (green flame)—up to 15 percent fuel, such as magnesium, that provides a very bright flame, and a binder, such as synthetic resins. Compounds that produce green and red flames also contain chlorine-containing additives, for instance, hexachlorobenzene or polyvinyl chloride. Good flame color can also be obtained by using ammonium perchlorate as an oxidizer and by partially replacing the binders with hexamethylenetetramine (urotropin).

Compounds for signal smokes contain 35–40 percent potassium chlorate or perchlorate, 20–25 percent hydrocarbons and synthetic resins, 40–45 percent thermally stable organic dyes capable of sublimation, most frequently fatty rhodamine orange, methylene blue, and anthraquinone dyes.

Pyrotechnic signals are used in sea and air transportation, in fireworks, and in the filming of motion pictures.