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Most
fireworks contain substances like potassium nitrate or saltpetre for
supplying oxygen. Substances
like charcoal and sulphur are
sometimes added because they combine with the oxygen to produce heat
and light. A mixture of saltpetre, sulphur, and charcoal constitutes
black powder, used for pyrotechnics before it was adapted for
military purposes. A large number of flammable substances, such as
starch, gum, sugar, shellac and other petroleum derivatives are
often used in the mixture instead of charcoal and sulphur.
Shortly
after 1800, people began to use potassium chlorate as a substitute
for some or all of the potassium nitrate in the explosive mixture.
Even today, potassium chlorate or potassium perchlorate is an
important ingredient in most fireworks mixtures.
How the colors
are produced
There is no describing the myriad colors that are produced by
firecrackers. The red color that we see is produced because
compounds of a chemical called strontium have been used. Using
copper compounds produces the blue color. Yellow is the result of
sodium being added to the gunpowder and white is produced when
magnesium is used.
How the sparks
are produced
Metal flakes are added while making firecrackers. It is these
flakes that produce the sparks. Metals like titanium
and aluminium are used
for this purpose.
The different
types
Fireworks are mainly of two types: force-and-spark and flame. To
make the first variety, potassium nitrate, sulphur and finely ground
charcoal are mixed along with additional ingredients that produce
the various types of sparks.
The second variety,
the flame, refers to the stars and colors that are produced when
(firecracker) rockets burst in the sky. To obtain the effect,
potassium nitrate, sulphur and salts of antimony are used. When you
see the stars bursting out in bright colors, do remember that
potassium chlorate (or potassium perchlorate) has been added along
with a metal salt.
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