Tag: fireworks

Chemistry of Fireworks – Bangs, Crackles & Whistles

The Chemistry of Fireworks: Bangs, Crackles & Whistles

Infographic on the chemistry behind firework bangs, crackles and whistles. Bangs are produced by the ignition of an explosive mixture, usually an oxidiser, sulfur and aluminium. Compacted, confined gunpowder also produces a loud bang. Crackling fireworks originally used a mix of lead tetroxide and magnallium, but now bismuth compounds are more commonly used. Whistling fireworks use aromatic organic compounds such as gallic acid tightly packed into a tube with oxidisers. Small explosions caused by these compounds lead to oscillations in the gases produced, creating a standing wave in the tube that gives a whistling effect.
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With the 5th of November approaching, the distant reports of early fireworks displays can already be heard in the evenings here in the UK. Discussion on the chemistry of fireworks usually centres on the compounds used to generate their array of colours, but there’s a whole lot of chemistry behind the sounds they make too. Here we take a brief look at some of the ways in which pyrotechnic chemists give fireworks their characteristic bangs and screeches.

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The chemistry of the colours of fireworks

Infographic on the chemistry of fireworks. Red fireworks: strontium salts. Orange fireworks: calcium salts. Yellow fireworks: sodium salts. Green fireworks: barium salts. Blue fireworks: copper salts. Purple fireworks: combination of strontium and copper compounds. Silver: white hot magnesium and aluminium. White: burning metal. Fireworks also contain fuel to allow the firework to burn, oxidisers to provide oxygen for combustion, binders to hold the mixture together and chlorine donors to strengthen some colours.
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The colours in fireworks stem from a wide variety of metal compounds – particularly metal salts. ‘Salt’ as a word conjures up images of the normal table salt you probably use every day; whilst this is one type of salt (sodium chloride), in chemistry ‘salt’ refers to any compound that contains metal and non-metal atoms ionically bonded together. So, how do these compounds give a huge range of colours, and what else is needed to produce fireworks?

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