Today we're going to be looking at a demonstration that's so simple that if
you're already familiar with it you may not have checked out your risk
assessments in a while. And if that's the case, then stick around because you could
be finding that you're doing it dangerously wrong. If not, then you're in
for a treat because this makes for a great alternative to demonstrations such
as the 'elephant's toothpaste' demonstration; this is 'genie in a bottle'.
As with any demonstration, on the EiC website you can find all of the details you need.
But we're going to start today with the safety information because I'm going to
be using some 100 vol. hydrogen peroxide, I'm going to be rocking the
splash proof goggles, I've got some gloves here, and we also need to have a
little bit of a chat about what kind of glassware we want to be using to perform
this demonstration. So I'm gonna be using some borosilicate flasks here with a
wide-ish neck between sort of 30 to 40 mm and I've got a bung that fits
nicely into there. Because people are sort of doing like a genie demonstration,
sometimes they can be tempted to use a volumetric flask because it has a
slightly more exotic shape. These are made out of the wrong type of glass, they have
these thinner, narrower, longer necks and have been known to explode in the past
during this demonstration. So absolutely never, ever, ever use a volumetric flask
for this demonstration. You can use a small PET [poly(ethylene terephthalate)] bottle. These are okay but you
might find that the heat during the demonstration causes them to deform a
little bit. So, once they've been used for one time just get rid of them straight
away afterwards. So, I'm all goggled up, but before I pop on my gloves I'm actually
going to load up my catalyst because I need to sort of tie some knots and
it might be a little bit fiddly if I'm trying to tie a knot in some string with some gloves on.
Now I've got here 0.5 g of manganese(IV) oxide
and I'm going to sort of make a little pouch using some tissue
paper. And I'm gonna tie that up with a piece of thread basically. The thread
needs to be long enough that I can tie up my knot and still have like about 10 cm
hanging out of the end of the flask.
Okay, so I've got a couple of pouches: time to pop my gloves on.
So, here's my 250 ml borosilicate flask.
You'll notice I'm using a special type of bung here which
has got a hole in it. That's really important because actually if the
catalyst were to drop into the peroxide too soon,
then if you've got a bung without a hole in it then you can actually and again
end up with risk of explosion. So this is going to just add an extra safety net for us.
So, making sure that you use a funnel,
because you don't want to be actually touching the sides of the flask,
we've got 25 cm³ of our 100 vol. peroxide
Okay, and that's loaded in there making sure that there
isn't any peroxide lurking for us on the side of the flask.
Get my catalyst.
Set it up so it's hanging above the liquid.
So, now I'm ready to go, I'm going to find that when the reaction starts, it's going
to be producing some aerosolised water, essentially some mist, but also
within there there's going to be some droplets of hydrogen peroxide. For that
reason we want the audience about 5 m away and protected behind some
safety screens. And because of that I'm going to take off my microphone, so that
in order to initiate all I need to do is take out the bung okay and the string
will drop in, the catalyst gets going, let's see what happens.
So, a quick look around at the area surrounding the demonstration afterwards
will give you a clue into why you want your audience a decent distance away.
And you can see these small particles of manganese(IV) oxide that have been
distributed around the area of the demonstration. It's for this reason you
absolutely don't want to be using lead oxide as a catalyst, because you will be
dispersing lead particles into the classroom. Either way, really quick, simple,
easy demonstration. Just check the risk assessments and of course CLEAPSS members,
if they have any special guidance that they want to look for, can get in contact
with CLEAPSS for a special risk assessment, as this demonstration is
unlikely to be covered by your model risk assessments. Give it a try and I'll
see you next time, thanks very much.