Flame Mixtures* Amount 10)
blue
red
yellow
potassium chlorate dextrin copper(ll)ammonium chlorideb laC1ose
16 12
4 6
strontium nitrate potassium chlorate dextrin barium nitrate
Sodium axalate
sulfur
dextrin pink
potassium perchlorate calcium sulfate dextrin
white
potassium nitrate suilur antimony sulfidec
12
3 3
' ~ ~ r n l x w e ebesrnrBdinamoI, ~ l d dryatrnosphersfortherninirnm~m~u~ttf
The demonstration device assembled and ready for use
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A particularly convenient arrangement that would facilitate the described apparatus is the assembly of a set of different test solutions-each different solution being stored in its own spray bottle. The set could also include a bottle of deionized water to be used between tests for clearing the current atmosphere inside the flame test device. Listine 20 different solutions that soan the colors of the Handvisibleuspectrum, The Chemical ~ u b b e Company's r book of Chemistrv and Physics (63rd ed., Flame and Bead ~ e s t s , ~ e c t i oD,n p 138) is in excellent resource for planning flame tests.
Vivid Flame Tests Sus~lrrm BY
David J. Ager,' Michael €4. East, and Robert A. Miller Unlverslty ol Toledo Toledo. OH 43606 CWCKEOBY
Alfred A. Schilt Northern lllinolr UnlversHy DaKalb, IL 60115 Flame tests can be extremely useful for lecture demonstrattms in qualitative analysi; and as an introduction to atomic absorption spectrometrv. flame test demon. A good . stration can.-however, present certain problems. When the metal salt is sprinkled or hlown into a flame, the color is ofwnshort-lived and not intense. If the room lieht cannot be " dimmed, some colors are almost impossible to see even with a small class size. If a " eas source is not available. an alcohol flame or a portable propane torch can be used, but again dim liehtine is reauired. .. ~ l t e r n a t i v emethods for the production of colored flames have beensuggested that require themixingofthe metal salt with a cvmbustible mixturesuchasgunpowder or potassium chlorateand sugar.' With such mixtures, we have found that ronsiderable experimentation is necessary to obtain a vivid color without the production of excessive amounrs of smoke or the masking df the color by the "parent" combustion process. As our chemical demonstrations are presented at a wide variety of schools and other institutions, we found i t necessary to have flame tests that (1) rely on an internal
time. ineither the snhydmus or dihydrateformsare suitabierubstitutes. bCwp~ii)miwlde 'Antimony potassium tanrate is a suitable substitute. combustion source, (2) produce avivid color that can be seen without the room light being dimmed, and (3)produce little smoke. Many teachers use the analogy of fireworks while demonstrating flame tests, and we have adapted tableau fires (the simplest form of firework) to our needs.3 All of the recipes fulfill our first two requirements, but some care must be exercised with the combustion byproducts, and use of a particular formula must be judged for the site of the demonstration. It is recommended that the white and yellow fire mixtures be ignited in a hood or open space as sulfur dioxide is produced. The intense colors allow the demonstrations to be performed in the open air as they are easily seen in a shaded area. The white fire has been included as the color of the mixture can produce some interesting discussion among students about the expected flame color. Preparation Ensure that all chemicals are dry and have not started to decompose through prolonged or improper storage. The ingredients should he around individually to a fine powder wjth a mortar and pestle. Once the required amount of a powdered chemical has been weighed out, the mortar and pestle should be washed thoroughly and dried (not with organicsolvents!). The ingredients for the required formula, once individually ground and weighed, should be placed in a 250-mL beaker and stirred thoroughly with a wooden soatula. Do not attemot to mind t h e mixture because spontaneous detonation~could~occur. The mixtures should be kept in a drv atmosohere until used. If stored, a plastic container is recommended, but the formula shoul'd bk used as soon as possible and not stored for prolonged periods.
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Author to whom correspondence should be addressed. Present address: NutraSweet Research and Development, 601 E. Kensington Rd.. Mount Prospect. IL 60056. Shakhashiri. B. 2. In Chemical Demonstrations; University of Wisconsin: Madison, 1983; Vol. 1, p 79. Weingant, G. W. Pyrotechnics. 2nded.; Chemical Publishing: New York, 1947. Volume 65 Number 6 June 1988
545
Formula Each mixture contains a chemical source of oxygen, a combustible material based on carbon or sulfur, and one or two metal ions as the color source (see table). Procedures Place 2 to 15 e of the reouired mixture. according to the room or demonstration site, on an asbestos sheet or Pyrex watch glass. The oink and white flame mixtures are surorisinglrd:lfficult to ignite, hut this ran hro\.ercome by placing a piece of wooden splint into rhr side of the pile. Ignite with a
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546
Journal of Chemical Education
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match at arm's length. Some of the mixtures produce smoke, and use of a hood is recommended. The white fire produces copious amounts of sulfur dioxide. This noxious gas is also oroduced during combustion of the vellow flame mixture. ~ h e s latter e mi&es must be ignited ih a hood or open space. The residues should he neutralized. if necessarv. and washed with water. Acknowledgment The authors wish to thank Philip Brehm, Dension University, Granville, Ohio, for the kind donation of reference 2.
