I forwarded this to the folks who do most of the demos here - and who helped develop the splint and flame version of this demo.
I've included what I received from Josh. I think his idea is pretty brilliant.
Debbie M. Decker, CCHO, ACS Fellow
Past Chair, Division of Chemical Health and Safety
University of California, Davis
Birkett's hypothesis: "Any chemical reaction
that proceeds smoothly under normal conditions,
can proceed violently in the presence of an idiot."
I'm a bit worried about that method, primarily because of the spray bottles themselves. Even assuming you have one rated to contain and deliver methanol, I don't think I've ever used a normal trigger-style spray bottle that doesn't drip, and most of the ones I've used over extended periods have eventually begun to leak. I think there's a good possibility of the flame tracing back to the nozzle, and if methanol has leaked down the side of a plastic bottle containing a significant quantity of fuel, I could see that going poorly. I would also never do the experiment with an adjustable spray nozzle, as one accidental twist would change a fine mist into an unexpected stream.
However, if you were to use a pocket sprayer (like this one, or this one), you could minimize a lot of those risks -- the total size of the bottle limits your fuel to 2 - 8 mL, and each pump can only deliver a measured quantity of mist, with no way to turn it into a stream. The bottles are cheap enough to be discarded if they ever start dripping or leaking, and they're generally designed to dispense alcohol-based cleaners or disinfectants, so they should hold up decently well. I'd personally be willing to try it with pocket sprayers, but I can't say for sure whether it's an acceptable method without testing it thoroughly.
Then again, I still think someone should test this demo with wickless alcohol lamps -- it's less impressive than a cloud of flame, but you could actually see all the colors going at the same time without resorting to open petri dishes.
On Tue, Oct 17, 2017 at 11:49 AM, Debbie M. Decker <dmdecker**At_Symbol_Here**ucdavis.edu> wrote:
What do we think? I'm interested in your perspectives.
From: ACS Division of Chemical Health and Safety [mailto:DCHAS-L**At_Symbol_Here**PRINCETON.EDU] On Behalf Of Patrick A Ceas
Sent: Tuesday, October 17, 2017 11:02 AM
Subject: [DCHAS-L] Rainbow Flame Method using a spray bottle?
Please excuse the cross postings.
With National Chemistry Week just around the corner, I am wondering if any of you allow your faculty to perform the "Rainbow Flame Demonstration" using spray bottles?
For this method there are a series of spray bottles, each with its own unique salt solution dissolved in methanol. Each bottle is sprayed at an open flame and you get a nice colorful "WOW!" result as the mist ignites (one spray bottle at a time, not all bottles at once). This would be done in a public space (all viewers seated at least 10 feet away, as per NFPA 45).
My faculty like this method because they say that the sprayed mist poses little risk. I would very much appreciate your comments, and if you do allow some method of the Rainbow Demo then what is your SOP if you don't mind sending (can send offline).
I am very much aware of the recent rainbow accidents, and I also have the ACS "A Safer Rainbow" video, so please don't reply with links to those various accidents. I do not, however, have any links to accidents caused by using this spray bottle method. If you are aware of such links then please do send those. Or, do you consider the spray bottle method to be an acceptable method? My gut tells me that it is not an acceptable method (there seems to be many variables with using spray bottles, including flashback potential), but I will gladly accept the wisdom of the group.
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