A Safer "Rainbow Flame" Demo for the Classroom

19 Comments 6:35 am




Demo instructions available here:
http://www.acs.org/content/dam/acsorg/about/governance/committees/chemicalsafety/safetypractices/flame-tests-demonstration.pdf
(note: this demonstration does not require barium chloride, which is toxic — the video demonstration does not include this compound)

A C&EN infographic on the demo is available here: http://cenm.ag/labdemo

A chemistry demonstration commonly known as the “rainbow flame” experiment has resulted in a number of serious injuries in classrooms in recent years. The experiment is meant to show how various metal salt solutions can create flames of different colors, but it can be unsafe if teachers use highly flammable solvents like methanol or ethanol in the procedure. To prevent future injuries, the American Chemical Society (ACS) Committee on Safety recommends that rainbow flame experiments involving flammable solvents be discontinued immediately. In this new video, Kim Duncan and James Kessler of the ACS Education Division demonstrate a much safer alternative using the same metal salts dissolved in water (rather than in ethanol or methanol).

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19 thought on “A Safer "Rainbow Flame" Demo for the Classroom”

  1. Thank you so much for this video. I'm a writer and am current writing a children's story based on the old Are You Afraid of the Dark series from the 90s and I wanted to come up with a cool but safe way for the kids in the story to make their campfire burn like a rainbow when they add their "Midnight Dust" to it for effect.

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  3. I remember this experiment very clearly from high school chemistry class being performed by my teacher and a lab assistant in front of each of my classes lab groups one group as a time and thought it was one of the “cooler” experiments because we could see the “Rainbow” of metal salts burning all at one time in beakers. For the life of me if this experiment is done properly (borosilicate glass beakers, less than 10ml of Ethanol (not Methanol), beakers extinguished and allowed to cool fully before adding additional metal salts or Ethanol, Never pouring Ethanol from bottle into beaker, lighting the beakers with a split from a meter or more away, and keeping students a meter or more away while the experiment is burning, and a lab assistant manning a fire extinguisher while the experiment is being demonstrated.) that this experiment can go wrong. My guess the reason that this experiment has gone wrong recently is the teacher added more solvent Methanol or Ethanol to beakers that are burning or still hot, in other words not following common sense lab safety protocol.

  4. We do this with Q-tip swabs soaked in the metal salts in water solutions. The Q-tip won't catch fire until well after all the metal salt has burned off and the students can see the color very well. They then put the used Q-tip in a beaker of water that is disposed of. Easy, safe and effective. Students love it.

  5. Using saturated solutions like this is wasteful and not needed. The old method using spray bottles and 0.1m (aq) solutions is far more effective. Use distilled water for the students and have an ethanol set for a demonstration by an experienced teacher or technician.

  6. I'm not surprised that safety is at the forefront here, given the most recent (completely avoidable) incident involving the methanol-solutions version of this demo. I do agree this is a far safer method for flame tests. But aren't we crossing over into paranoia to recommend an impact shield for holding some soaking wet wood splints into a burner? I'm all about keeping kids (and teachers!) safe, but this just seems way over the top. Maybe everyone in the room should wear respirators or haz-mat suits while are at it? 😉 These kinds of blanket statements (whether they are from the National Fire Protection or re-stated by the ACS) do have a cost associated with them: unnecessary bans and impediments to great science teaching.

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