Monthly Archives: December 2014
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A glow stick is a self-contained, short-term light-source. It consists of a translucent plastic tube containing isolated substances that, when combined, make light through chemiluminescence, so it does not require an external energy source. The light cannot be turned off, and can be used only once. Glow sticks are often used for recreation, but may also be relied upon for light during military, police, fire, or Emergency operations.
|Chemistry of Glow Stick Colours|
A glow stick contains two chemicals and a suitable dye. The chemicals inside the plastic tube are a mixture of the dye and diphenyl oxalate. The chemical in the glass vial is hydrogen peroxide. By mixing the peroxide with the phenyl oxalate ester, a chemical reaction takes place, yielding two molecules of phenol and one molecule of peroxyacid ester (1,2-dioxetanedione). The peroxyacid decomposes spontaneously to carbon dioxide, releasing energy that excites the dye, which then relaxes by releasing a photon. The wavelength of the photon—the color of the emitted light—depends on the structure of the dye.
As stated by the excellent article by Compound Interest, a range of different chemicals can be used, including those shown above, as well as one or two additional dyes. Whilst the molecules of the dye are always present in the solution, the hydrogen peroxide and the diphenyl oxalate are slowly used up by the reaction, until one runs out and the reaction ceases – and it’s at this point that the glow stick will stop emitting its glow.
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It’s that time of year when we think about whether to get a ‘real’ Christmas tree or whether to get the artificial one out of the loft to decorate.
One of the problems of real trees is needle drop. First you have to decorate the tree without getting too many injuries from the sharp needles. Then you have to face the task of collecting the fallen needles on the carpet as the tree slowly withers.
Scientists have looked into the problem of needle drop.
Researchers identified a plant hormone, ethylene responsible for needle loss in balsam fir. They made the discovery by placing fir branches in containers of water inside a growth chamber. After ten days the branches began to produce ethylene and three days later the needles began to drop. After 40 days, the branches were completely bare.
To test that the needle loss was in fact due to the ethylene, the researchers used two chemical compounds that interfere with this hormone: 1-MCP and AVG. After exposing the branches to one of these two products, the needle retention period rose to 73 and 87 days, respectively.
It should be possible to dissolve AVG in the water added to the tree stand, which would prolong the tree’s lifespan indoors. Any Ethylene inhibitors should work.
There are other ways to prolong the life of your tree.
Choose your tree carefully. Norway spruce (traditional choice but with a quick needle drop rate); Nordmann fir (dark green and expensive but also boasts of a slow needle drop); Noble fir (the king of Christmas trees and again holds a better track record of needle drop than the Norway spruce); Fraser fir (excellent needle-holding properties and a lovely pine fragrance to boot and resembles the Norway spruce).
Make a new cut on the stump when you first buy it or get it home, at least an inch above the previous cut. Put the tree in water immediately, and maintain the water level. Keep temperatures in your home slightly cooler, if possible, and position the tree away from the kitchen. Also, keep fruits away from the tree as they give off ethylene. Lastly, leave the lights on at night. Being left in the dark causes a tree to respire more, using up its carbohydrates. As a result, says Dr. Raj Lada of the Christmas Tree Research Center, “it can be starved to death.”
Above all else – decorate and enjoy – don’t eat all the chocolates on the tree before Christmas!
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