[neact] Re: More on HS chlorate explosion-tsw reply
- From: Morgan Hanna <mhanna@xxxxxxxxxxxxxxxxx>
- To: neact@xxxxxxxxxxxxx
- Date: Fri, 22 Jan 2010 22:01:34 -0500 (EST)
A number of years ago I read that when working with potassium chlorate you need
to make sure your glassware is clean(no hydrocarbons). This used to be a
standard high school lab heating up the potassium chlorate and determining the
yield of KCl. Unfortunately it periodically exploded covering the students in
broken glass. Instead of having the students perform this experiment, today I
think most of us do this as a demo with the gummy bear illustrating a number of
topics in chem. I use new test tubes and perform the reaction behind a
splash/blast shield. I hope this great demonstration does not become deemed too
dangerous. It is a memorable teachable moment that my past students remind me
about.
----- Original Message -----
From: "Jerusha Vogel" <jj@xxxxxxxx>
To: neact@xxxxxxxxxxxxx
Sent: Friday, January 22, 2010 7:10:49 PM
Subject: [neact] Re: More on HS chlorate explosion-tsw reply
Oops, I knew that – thanks for the correction. It was KClO3 that I used. That’s
what comes from typing when the kids are clamoring for food. So you think this
demo could be used successfully and more safely with the potassium perchlorate?
JV
From: neact-bounce@xxxxxxxxxxxxx [mailto:neact-bounce@xxxxxxxxxxxxx] On Behalf
Of Ted Wysocki
Sent: Friday, January 22, 2010 6:40 PM
To: neact@xxxxxxxxxxxxx
Cc: ted w
Subject: [neact] Re: More on HS chlorate explosion-tsw reply
As I read throught the e-mails I find that KClO4, which is actually Potassium
Perchlorate, is being referered to as Potassium Chlorate. Potassium Chlorate is
KClO3.
I have worked with both in an explosives/ pyrotechnics company, and found
formulations using as the oxidizer KClO4 being less sensitive than those made
with Potassium Chlorate.
We also found slight traces of copper or copper compound increased the
sensitivty.
Could someone tell me which of these two compounds was used, ...that resulted
in the explosion?
Ted.
Date: Fri, 22 Jan 2010 17:37:00 -0500
From: jj@xxxxxxxx
Subject: [neact] Re: More on HS chlorate explosion
To: neact@xxxxxxxxxxxxx
This is a very popular demo with the kids and I have done this many times with
the gummy bear with no problems. You heat a pyrex test tube with a small amount
of KClO4 over a Bunsen burner. It liquefies and decomposes. You can see a white
cloud of gas moving up the test tube. At this point I do the oxygen test to
show the kids the identity of the gas and then to finish it off, I throw a
gummy bear in. A light purple flame that looks like a blow torch comes shooting
out as the sugar reacts – it’s a great demo that can demonstrate flame tests,
types of reactions, and even review the electron movement in the potassium atom
causing the violet color! My colleague was doing this same demo in the hood in
front of her class when the oxygen produced got trapped under some liquefied
KClO4 and cause it to splatter outward violently. The teacher was burned on her
hand and wrist by the molten KCl. Since it was in a hood no kids were hurt, but
we started using heavy gloves when doing the demo. My school had the hood in
the middle of the room so the kids could be on one side looking through the
glass, while I was on the other with the glass partly up to reach in. That made
it even safer for the kids – but few rooms are set up that way.
Jerusha Vogel
From: neact-bounce@xxxxxxxxxxxxx [mailto:neact-bounce@xxxxxxxxxxxxx] On Behalf
Of Lois Ongley
Sent: Friday, January 22, 2010 5:00 PM
To: neact@xxxxxxxxxxxxx
Subject: [neact] Re: More on HS chlorate explosion
Speculation would indicate that it was just potassium chlorate heated with
stick of gum dropped in. A common enough HS experiment on You tube as gummi
bear sacrifice.
Lois Ongley
From: neact-bounce@xxxxxxxxxxxxx [mailto:neact-bounce@xxxxxxxxxxxxx] On Behalf
Of Kenneth Bowers
Sent: Friday, January 22, 2010 4:49 PM
To: neact@xxxxxxxxxxxxx
Subject: [neact] Re: More on HS chlorate explosion
I have conducted what I believe is the same experiment many times.
I always have done the experiment outside.
Can you provide more information on the catalyst used ?
Was concentrated sulfuric acid part of the experiment ?
Retired now from full time teaching. I still work on a regulart basis as a
substitute.
Kenneth Bowers
On Jan 22, 2010, at 12:22 PM, Stephen Stepenuck wrote:
Some follow-up info on the high school potassium chlorate explosion. This too
is from the ACS Division of Chemical Health and Safety’s email list.
This account seems to me to be a strong argument for purchase and use of
portable safety shields, and long heavy gloves for the teacher.
[Apologies for accidental post earlier. Maybe when I’m 137 I’ll learn to
triple-check the address line...]
Steve
* * * * * * *
New York
http://www.dailyfreeman.com/articles/2010/01/21/news/doc4b57e5a7a5748273921860.txt
Teacher recovering; cause of blast uncertain
Published: Thursday, January 21, 2010
By JAY BRAMAN JR.
Correspondent
BOICEVILLE — The explosion on Tuesday that injured an Onteora High School
chemistry teacher and seven of his students came as a surprise to everyone, but
probably no one more than the longtime teacher himself.
Donald Bucher was demonstrating an experiment with the chemical potassium
chlorate when the explosion — which was strong enough to damage a window in the
classroom — occurred. Onteora school district Superintendent Leslie Ford said
on Wednesday that Bucher had conducted the same experiment dozens of times
before, without incident, and that the cause of the explosion remained a
mystery.
Ford said Bucher was resting at home on Wednesday, recovering from his injury,
and that an investigation of the incident will begin shortly.
“We still don’t know what happened,” the superintendent said. “But we will
debrief Mr. Bucher when he is well enough to return.”
Ford said a small piece of glass punctured Bucher’s arm and cut an artery. “He
was bleeding quite a lot,” she said.
A reporter’s calls to Bucher’s home were not answered on Wednesday.
The seven students who were injured, all 11th-graders, were treated at Kingston
and Benedictine hospitals, primarily for minor cuts, and released.
Ford said the explosion occurred when Bucher dropped a stick of gum into a test
tube containing potassium chlorate, a chemical used in matches, explosives,
gunpowder and fireworks.
Ford said school district officials reviewed the chemistry class’ lesson plan
and concluded the experiment had been performed safely by Bucher in the past.
She also said it is a standard high school chemistry experiment and that Bucher
executed each of its steps properly on Wednesday.
“The goal of the experiment was to determine the amount of oxygen in the
potassium chlorate,” Ford said.
The superintendent said possible causes of the accident were a faulty test tube
or the chemical itself being compromised.
All the remaining potassium chlorate in the classroom was removed, bagged
locked in a secure location elsewhere in the building by Michael O’Rourke of
the Risk Management Department at Ulster BOCES, Ford said.
O’Rourke said on Wednesday that the chemical will be disposed of properly and
other chemicals in the school will be checked for problems.
According to a Web site co-maintained by the National Oceanic and Atmospheric
Administration, potassium chlorate is a white crystalline solid. It is used in
matches, explosives, gunpowder and fireworks; as a disinfectant; and as an
oxidizing agent. It forms a flammable mixture with combustible materials, and
the mixture can be explosive if combustible material is finely divided.
Potassium chlorate can be ignited by friction, and contact with strong sulfuric
acid may cause fires or explosions, according to the Web site. Also, it may
spontaneously decompose and ignite when mixed with ammonium salts and may
explode under prolonged exposure to heat or fire.
Ulster County Emergency Management Director Art Snyder appeared before the
Onterora Board of Education during the body’s regularly scheduled meeting
Tuesday evening. He outlined the procedures for hazardous materials disposal,
though Ford noted the procedures were not required in Tuesday’s incident.
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