I do this demo every semester with my lab safety training for every section of every lab. I got it, I believe, as a Flinn Notes, many years ago. You use disposable petri dishes, draw eyes on bottom of each with marker, place an egg white in each, then place on document reader (we used to use an overhead projector) and add drops of 18 M Conc. H2SO4 to the first one, and have them count seconds until it is opaque (less than 3). Then put 20 % or higher NaOH, about 2-5 mL (liquid plumr or draino work too) in other dish, and mix. I use a gloved hand, because it turns solid like jello- jiggler within a minute or two, so it becomes possible to pick up the egg white. It does not change color. Within 5 minutes or so, you can turn the dish over without the egg white being able to run out.
The message then is, we don’t have the time to get to the eye wash if we let anything this concentrated get into our eyes. The eyewash is only an effective remedy for something this concentrated, if the splash guard safety goggles KEEP IT OUT OF OUR EYES and give us the time to wash it off. Then, all semester, a two second reminder about cooking eyes is all it takes to get them to keep those goggles on, as they need to.
Lead Chemistry Instructor
Western Technical College
400 7th St. N.
LaCrosse, WI 54601
"It's better to be careful 100 times, than to be killed once."
I first saw the "egg" demonstration in a J. T. Baker safety course in 1978. Two eggs were used. One egg was placed in concentrated sulfuric acid and the other in a concentrated (6 M) sodium hydroxide solution. I do not recall the length of time each substance was in contact with the egg.
The egg in the sulfuric acid was "cooked" from the outside in. The egg yolk stayed fluid. Our instructor stated this the the effect of a corrosive material.
The egg in the sodium hydroxide solution was "cooked" from the inside out. The yolk was "hard" while the egg white was relatively fluid. In this case our instructor stated this was the effect of a caustic material.
David A. Katz
Chemist, Educator, Expert Demonstrator, Science Communicator, and Consultant
Programs and workshops for teachers, schools, museums, and the public
133 N. Desert Stream Dr. * Tucson, AZ 85745-2277 * USA
voice/fax: (520) 624-2207 * email: dakatz45**At_Symbol_Here**msn.com
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----- Original Message -----
From: Stephen Stepenuck
Sent: Saturday, February 07, 2015 2:45 PM
Subject: Re: [DCHAS-L] DCHAS-L Digest - 4 Feb 2015 to 5 Feb 2015 (#2015-16) Eye protection education
1. Re Mel Charlton's post about the eye protection video, I agree with
David Katz, et al. that it was most likely Norman Quam's production, where
they painted mannequin heads with solutions of Fe(III) or thiocyanate, and
exploded flasks containing the other reactant, causing red spots/blotches
wherever the eye/face protection had failed, or not covered. Someone should
certainly resurrect and reproduce that video, rather than "reinvent the
wheel," as Mel says [if only for the safety implications].
2. Re the suggestion of using NaOH in a Petri dish as a demo, I haven't
seen anyone mention a variant that I have found to be strikingly effective
when trying to "reach" people [young academic, or older industrial types] to
wear their eye protection *all* the time: It was not my idea, and I can't
remember where I first saw it to give the inventor credit, but: separating
the white of an egg, telling the students that that is similar to [some]
tissue in the eye, then putting that in a Petri dish on an overhead
projector [if you can find one that works] then asking the class to count
the time before my added drop of concentrated HCl [i.e. not base] coagulated
the previously transparent egg white, frequently yielded outright gasps from
the audience. Of course, the "instant cataract" projects black on the
screen. Then all the instructor need do was ask "Could YOU see through
that?" and/or "Could you beat that to the eye/face wash?" and the point was
made. I had much less trouble enforcing eye protection after that demo.
Suggestion: I would NOT tell them what the chemical was, except that it
was a very common one that they had all probably used, nor that this type of
damage might be repairable by eye surgery, whereas that from a base would be
much more difficult, if even possible, to repair.
Stephen J. Stepenuck, Ph.D.
Professor of chemistry emeritus
Keene State College
Keene NH 03435-2001
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