Table 2. Tltles of Colors of Transltlon Metal Complexes Demonstrations' Markus K m e t m Allan Weber Dave Bracken Nate Yates Grant Taylor Tracy Croll Rhonda M w r e Craig Refosco Craig Arnold Sondra O'Block Daneen Charlett
"Patriotic Colors of Co(l1) in Organic Solvents" "A Rainbow Array of Nickel Complexes" "Chioro and Thiocysnato Complexes of Cobalt(ll1)" "Red, White, Blue iron(ll)/(lll) Complexes" "Precipitates and Complexes of Ag(1)" "Prussian Blue" "Precipitates and Complexes of Nickel(1l)" "Precipitates and Complexes of Iron(ll1Y "lodo Complexes of Mercury" "Bromo Complexes of Copper" "Precipitates and Complexes of Cobalt(1lY'
tor and the runner up a t the local restaurant of the winner's choice. These included some very nice and not inexpensive establishments, and the tab was to be picked up hy the instructor! The second prize was having to have lunch with the winner! The titles of the demonstrations performed are given in Table 2. Each demonstration was also reported in a normal lahoratorv renort. The respo1;se by the students was most favorable. They liked the flexibility and choice involved. Some went to great extents to put on a good show. One student dressed as a magician with a black cape and top hat. One prepared a very nice poster to complement her explanation. Several had written out all the pertinent equations on the hoard heforehand and/or prepared attractive overhead transparencies. One did a rather extensive search of the literature to prepare for the session. In general there was some good, constructive competition to see who would win the prizes. Some had difficulties doing the demonstrations. In some cases, they were not as well prepared regarding the experimental method as thev should have been. Several were rather badlv blistered, hot by the chemicals involved, but by the questions thrown a t them, not all of which came from the instructor. Several noted they had learned a great deal, not only about their particular system, but how to prepare for an oral presentation. I t was apparent that each gained some valuable insieht - on what it takes to talk chemistry in front of a group. In addition to making progress toward fulfilling the goal of increasing oral communication skills on a technical subject, other positive advantages were realized. First was the increased interaction between instructor and individual student. We all look for a variety of ways to increase that interaction. We cannot help students most effectively by just lecturing to them. Any and all out of class interchange helus build a relationshin throueh which we influence. couusel;andjust enjoy theco~pany~fourstudents.Thisa~tivity brought students. ~articularlvthose I did not know well, intu my office earlier a i d more oiten. Second, there was appreciable discussion among students themselves on the tecbnical subject at hand. I v h e any activity that promotes students learning from each other and comparing notes on their studies. Thirdly, students (often in consultation with their peers) had to deal with problems that were often unexpected and not explained in the text of the source of the demonstration. Examples of these problems were the nature of a hydrate, how to handle organic solvents, the danger of potassium cyanide (why is putting it in an acid a hazard?) and the ever-present problem of remembering how to make up solutions of various concentrations. Lastly, there were several situations in which the color changes could not be fully explained by the simple crystal field theory, which I develop in this sophomore inorganic course. A better explanation is afforded by the adjusted crystal field theory using TanaheSugano diagrams, etc. (which I teach in the post-Physical 544
Journal of Chemical Education
Chemistry Advanced Inorganic course). At first I feared that this might be a disadvantage to student-selected demonstrations hut I found that with some thoughtful and selectedly simplified explanations, some students were stimulated by this reference to these more advanced topics. I think one or two of them enrolled in the second course as a result of this exposure to these systems. In conclusion, my students and I found this activity valuable and worthy of our time. We encourage you and your students to give it a try. Literature Cited 1. Rurkeft. A. R.: h n k l e , S . B. J , Chcm Edur. 19R3.fi0.469. 2. C n d r n m M' D.: Rean..l.I'.-I. Chrm Edac. 19fi1,6O, 488. 3. Lngoai~,.l..T .l.rhrm. M u r . 19Rd.6I.RI2 4. J. rhrm Edur. 1985.62. 14. 5 1.ahianea.D. A ; Rwver. W . I . J . rhrm Edrrr. IWS. 62,400. R Afhioo.C F .I. Chem Fdul 19Rq.fi:I.Bli. 7. l C h c r n d u r . 1987,El. I l l 8. Rodger.,(;. E.: l.andoll, H . I: I.r h r m Edsr. 1973.50.7ffi. 9. Rndwri.C F 4.rhnm.Mur. 19P1.61.9911. 10. .I. Chrm E C r 19R7.64.104. I I . Rlmeft?. R. W. .I. Chem. Edur. 19RO.S7.fin. 12. Ramelle,R. W . J Chrm. Educ. 19~4;6l,ffi0. I?. Chen. I ' S. Enfrrloinin~ond EdacntinnaiChsmirnl lhmonstrations:Chemical Elements: Camnrillo.~~,'1974. d ~ d in chemirtry.6th d.; uiviaion 14.A I Y ~H.~ ,N.;uatton.F B. ~ ~ nsmonstrntinns Chemical Fducafion:Easton, PA. 1965. IS. Shakhnrhiri,B.7. Chcmicol D*monsfmtions,A Handbook for Teoehersoichemistry: Univer.iity of Wirconnin: Msdison. WI, 1983;Val. I.
A Flame Test Demonstration Device SUBMITTED BY
Edward M. Gouge PresbyterIan College Cllnton, SC 29325 CHECKED BY
George Wollaston Clarlon Univerrlty Clarion. PA 16214
The \.slue of flame tests in contemporary chemical educatiun rannut be understated. Elemental analvsis. descrinrive chemistry, and the quantum theory of matt& are just three examples of topics whose development in the classroom can he strengthened by one or more flame test demonstrations. Indeed, student fascination alone can in some cases justify the time spent displaying the beautiful, alluring array of elemental colors. A simnle. inexnensive. homemade device can enable a classroom leader'to demonstrate intensely colored, longlived flames that in most cases can be observed easily by a large group of students a t one time. Materials for constructing the device, which can best he described as an exhaust hood for a lab burner, are a 2-L plastic soft-drink bottle and an atomizer from a spray bottle that is manually pumped (hair spray bottles are a convenient source). Using a razor, the bottom of the bottle is removed and a hole large enough toadmit burner tubing is cut in the bottle near the neck. The barrel of a common Tirrill burner is removed and inserted into a cork or rubber stopper through which an appropriately sized hole has been bored; the stopper itself should have a diameter lareer than the diameter of the bottle's mouth. With the base of the burner placed inside the bottle and the gas hose run through the hole and connected to the base, the barrel is inserted through the bottle's mouth and reattached to the base of the hurner. The whole assembly is then suspended with a utility clamp attached to a support rod. A drawing of the assembly ready for demonstration is shown. After the burner is struck and the flame is adjusted properly, a saturated, aqueous solution of the element whose chiracteristic flame i s to be observed is aspirated into the open part of the soft drink bottle using the atomizer. The aerosol, after being exhausted through the barrel, will produce an intensely colored flame that lasts several minutes.
Flame Mixtures* Amount 10)
potassium chlorate dextrin copper(ll)ammonium chlorideb laC1ose
strontium nitrate potassium chlorate dextrin barium nitrate
potassium perchlorate calcium sulfate dextrin
potassium nitrate suilur antimony sulfidec
' ~ ~ r n l x w e ebesrnrBdinamoI, ~ l d dryatrnosphersfortherninirnm~m~u~ttf
The demonstration device assembled and ready for use
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.
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