Flame tests

The ideal heat source has a high temperature and produces a non-luminous flame. The Bunsen burner is ideal. The next best flame is again refined heavy oil – hot and non-luminous. Spirit burners produce a non-luminous flame at much greater cost, unless methylated spirits are used as fuel in which case the flame is much cooler. A butane lighter produces a very hot flame of sufficient size and time for flame tests although the non-luminous region is small. Kerosene stoves will work for some salts, especially if you pull the wicks longer or remove the outer protective shell (usually green) to give students access to the hotter blue flame in between the inner shells. As can be seen by the above discussion, alcohol infused heavy oil burners provide the best compromise heat source. They are also the easiest of these heat sources to use – pour the fluid into an open-topped metal container and set it on fire. They are also the safest heat source – they produce no smoke (unlike kerosene and candles), do not have fuel that spreads when it spills (kerosene and ethanol), nor can explode like gas. Students do not have to hold the burning apparatus (as with a lighter) and the flame may be extinguished by simply blowing it out or smothering it with a lid. Finally, the burners themselves are free – soda bottle tops, medicine and liquor bottle caps, cut aluminum cans, and metal tins; different sizes for different size flames. If you have access to this fuel, we strongly recommend using it. No matter which heat sources you use, always have available fire-fighting equipment that you know how to use. See item 5 in Specific Guidelines to Reduce Risk for more about fires. Remember that to put out a Bunsen burner safely, you need to turn off the gas.

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