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Structure
Interesting Questions, Facts and Information
- There are a total of 10 general entries.
Special Topics
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 Interesting Questions, Facts, and Information
 Chemistry
carmine. Carmine is a very large metal complex with an aluminium ion at its centre. It is used as a biological stain in medical laboratories. It takes 70,000 insects to produce one pound of carmine! In solution form, it is known as cochineal extract and is used as a food colouring.
| The gemstones ruby and sapphire are both forms of aluminium oxide - alumina (Al2O3). Their different colours are caused by metal ion impurities replacing aluminium ions at random points throughout the structure. Which metal ion impurity is responsible for ruby's red colour? | The Very Colourful Chemistry Quiz
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chromium 3+. Once again, the wavelength of the light absorbed by the substance in question is what gives it its colour. The inclusion of the metal ion impurities into the alumina structure alter the wavelength of light that is absorbed, and therefore the colour of the stone. Alumina with both iron 3+ and titanium 4+ impurities gives the blue stone known as sapphire, while alumina with iron 3+ impurities gives the amber-coloured stone known as topaz.
lycopene. Lycopene has a very similar structure to carotene, which explains their similar colours. Lycopene is also found in pink grapefruit, guava and watermelon. A number of studies have suggested that lycopene may be a useful cancer-preventative agent.
melanin. Melanin is a dark brown/black pigment also found in skin - the amount determines how dark or light your skin is. Freckles are small concentrations of melanin. Hair also contains another pigment called phaeomelanin, which is a red-brown or yellow-brown colour. The relative amounts of melanin and phaeomelanin in your hair determine its colour.
lawsone. Lawsone is another organic molecule that absorbs visible light, making it coloured. A common feature of all organic molecules that absorb visible light is conjugation - this means that the molecule contains alternating single and double bonds. The more extensive the conjugation, the stronger the absorption. The "-one" in the name lawsone refers to the presence of ketone (C=O) groups. These are in conjugation with a benzene ring in lawsone, giving an extended conjugated system.
carotene. I was surprised to learn that the pigment that gives carrots their orange colour is also responsible for giving oranges their colour, too! Carotene is a large organic molecule that absorbs light at around 450 nanometres (the blue region of the visible spectrum), meaning that it appears orange. Green oranges contain chlorophyll in their skins, but this is gradually lost and replaced with carotene as the fruit matures.
chlorophyll. The chlorophylls are large organic molecules with a magnesium ion in the middle, a kind of molecule known as a metal complex. There are two different types of chlorophylls; a and b. The two types differ only in the type of side chain attached to one of the carbon atoms in the molecule. Chlorophylls absorb light in the 640-660 nanometre range (in the red region of the visible spectrum) meaning that they appear green or blue-green, which is the complementary colour to red.
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