This article is from the Pyrotechnics FAQ, by Hans Josef Wagemueller firstname.lastname@example.org with numerous contributions by others.
Gallic acid (3,4,5-trihydroxybenzoic acid)
This is used in some formulas for whistling fireworks. Whistle mixes
containing gallic acid are generally the most sensitive of the whistling
fireworks, with high sensitivity to both friction and impact when used
with chlorates, but cannot be used with perchlorates either. There are
safer alternatives for whistle compositions.
Gum arabic (Gum Acacia) -- Binder
An example of the various wood-resin-based adhesives used to bind firework
compositions. Others used include Red Gum and Gum Copal.
Black powder is the mainstay of pyrotechnics. At a basic level it is
a mixture of potassium nitrate, charcoal and sulphur. However, simply
mixing these ingredients together will not produce proper black powder.
It merely produces a much milder version, which itself is used
extensively in pyrotechnics, and is commonly called meal powder.
True black powder takes advantage of the extreme solubility of potassium
nitrate by mixing the very fine milled ingredients into a dough with
water, then using strong compression to force the water out of the
mixture, so that tiny crystals of potassium nitrate form in and around
the particles of the other ingredients. This produces a product that
is far fiercer than the simple meal powder.
Hexachlorobenzene, C6Cl6 -- Colour Enhancer
Used as a chlorine donor in coloured compositions that require one.
Rarely used, with PVC, Saran and Parlon being preferred.
Hexachloroethane, C2Cl6 -- Smoke Ingredient
The basic ingredient in many military smoke formulas. Not often used
with inorganic smoke mixtures, except those containing zinc.
Iron, Fe -- Fuel
The metal filings are used mainly in gerbs to produce sparks. Iron will
not keep well in firework compositions, and so it is generally pre-coated
with an oil/grease. One simple method is to add 1 gram of linseed oil to
16 grams of iron filings, mix, and boil off the excess oil.
Linseed oil -- Stabilizer
Used to coat metal powders in order to prevent them from oxidation, both
prior to use and in the firework composition. Polyesters are used in
commercial fireworks, but linseed oil remains an accessible option to the
Lithium carbonate, Li2CO3 -- Colouring Agent
Used to colour fires red. It has no advantage over strontium salts for
the same purpose.
Magnesium, Mg -- Fuel
Used to produce brilliant white fires. Should be coated with linseed oil/
polyester resin if contained in a composition which is not to be used
immediately, as it may react with other components of the mixture. The
coarser magnesium turnings are sometimes used in fountains to produce
crackling sparks. Magnesium-aluminium alloys give similar effects, and
are rather more stable in compositions.