The Earth Story

In Your Element! The Chemistry of Fireworks

The art of using mixtures of chemicals to produce explosives is an ancient one to say the least. Black powder - a mixture of potassium nitrate, charcoal, and sulfur - was being used in China well before 1000 AD and is also used in military explosives, construction blasting and, of course, fireworks. Years and years ago fireworks just used to be basically rockets and loud bangs and the colours such as orange and yellow came from charcoal and iron fillings. However, great advances in chemistry in the 19th century had new compounds finding their way into fireworks. Salts of copper, strontium, and barium added some brilliant colours. Magnesium and aluminum metals gave a dazzling white light. So, how do fireworks actually produce these brilliant colours and rather loud bangs? Well, it’s all thanks to nature’s elements and chemistry. There are really only a handful of different chemicals that are actually responsible for the most spectacular effects. To produce the noise and flashes, an oxidizer, (something that has a strong affinity for electrons) is reacted with a metal such as magnesium or aluminum mixed with sulfur. The resulting reaction produces a brilliant flash, which is due to the magnesium and aluminum burning, and the rapidly expanding gases produce a loud bang.

For a colour effect, an element with a coloured flame is included. Yellow colours in fireworks are due to sodium, strontium salts give the red colour and barium salts give the green colour. Achieving the vivid white flashes and the brilliant colours requires complex combinations of chemicals. For example, because a white flash produces high flame temperatures, the colours tend to wash out. Another problem arises from the use of sodium salts. Because sodium produces an extremely bright yellow colour, sodium salts cannot be used when other colours are desired, (It would be worth checking out the energy states of atoms that goes into more detail about the colours that elements give off during different energy levels).

In short, the manufacturing of fireworks that produce these desired effects requires a very careful selection of chemicals. People have even written books on the subject; there is an entire plethora available. No wonder fireworks cost so much!

~ JM

Image Credit: http://bit.ly/1zaRnEs

More Info: Check out this very informative short video explaining the chemistry in more detail: The Chemistry of Fireworks – Reactions:http://bit.ly/1pEedlY

Atomic Spectra - Interactive: http://bit.ly/1FVECSa

Flame Coloration by Element: http://bit.ly/1Cch6i0

Benitoite: California's state gemstone.

This blue lovely is only found in sizes larger than sand grains in one location worldwide, the mines in San Benito county of California located at the headwaters of the river bearing the same name. Discovered in 1907, it is a very popular collector's piece with American mineralogists. Many specimens have a greyish colour component added to their usual blue-violet, and the shade of this specimen is exceptionally fine. Chemically it is a barium titanium silicate. Benitoite fluoresces a beautiful sky blue shade in UV light (see our past post on glowing diamonds for an explanation of fluorescence at http://tinyurl.com/kebod3b).

It occurs in association with several other rare minerals, including neptunite and natrolite, and results from an uncommon association of geological forces. Hot fluids percolate through serpentine (altered olivine, see our past post at http://tinyurl.com/kjxc3es). The rarity comes from the particular chemistry of these hydrothermal solutions, combining elements in unusual combinations. It is suggested that fluids that had leached elements from two different geological formations mixed within the serpentine. How these formed is still poorly understood though they were metamorphic, The veins of serpentine (possibly old altered dykes) occur within brecciated grey-green glaucophane schists. Such schists are usually formed when a piece of crust is partly subducted and then springs back up due to its greater buoyancy than the mantle, being metamorphosed on its plunge down and bouncing up so fast the new minerals don't have time to return to their original form. Such minerals are known as metastable, ie existing outside their formation environment.

Its colour is probably caused by the same combination of iron and titanium passing electrons back and forth as blue sapphire. It is strongly dichroic, exhibiting different colours when viewed from different angles.

With a Mohs hardness of 6.5 faceted gems are used in jewellery, mainly expensive and unique designer pieces from California. Supply cannot keep up with demand, so prices are high, and since the mine is getting depleted, this situation will continue into the future, unless a new deposit is found.

Loz

Image credit: marinminerals.com

http://www.benitoite.com/benitoite/benitoit.shtml http://www.statesymbolsusa.org/California/gemstone_benitoite.html http://www.galleries.com/Benitoite A visit to the mine: http://luminousminerals.com/benitoite.shtml http://webmineral.com/data/Benitoite.shtml http://www.mindat.org/min-624.html

Uranocircite  Uranium minerals, despite their radioactivity and toxicity tend to have vivid and pretty colours and nice forms making for attractive specimens, despite their special storage and handling needs. They are also very soft and flaky so caution must be exercised when handling them and the hands thoroughly washed afterwards. The example in the photo is a barium uranium phosphate containing water in its structure, and commonly occurring in bright yellows and greens. The name comes from the Greek for falcon (and the associated goddess Circe), since it was discovered in Falkenstein (falcons stone) in Germany. It is a secondary mineral, formed by alteration of primary ones by the chemical action of the waters within the Earth commonly found in quartz veins. It is rare, but popular among collectors due to its beauty. Crystals are commonly square to tabular, but bladed aggregates such as this one and crusts are also common.  It converts to meta-uranocircite as it inevitably dehydrates, losing the water holding the plates together, and it should therefore be stored in a sealed container away from other minerals since the radioactivity might affect their colour and only handled occasionaly. Uranium minerals are also commonly fluorescent, emitting visible light when exited by the higher energy wavelengths of ultraviolet which bumps electrons up a shell within the atom. The visible light is emitted when the electron returns to its normal rest state due to the law of conservation of energy. Uranocircite's glow is a bright green. Sources include Bergen in Germany, Brazil, Cornwall, the USA, Zaire/DRC and France. The specimen in the photo comes from Minas Gerais in Brazil, and measures 4.9 x 3.2 x 2.4 cm. Loz Image credit: Rob Lavinsky/iRocks.com http://www.dakotamatrix.com/mineralpedia/7348/uranocircite http://www.galleries.com/Uranocircite http://www.mindat.org/min-4105.html http://webmineral.com/data/Uranocircite.shtml#.VGul68lQBZ4