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Rough Science 6 Colorado: Safety Video Diaries: Jonathan Hare

Updated Wednesday 9th November 2005

Exclusive video extra in which Jonathan Hare talks about the challenge for the Safety programme, from the sixth BBC/OU TV series Rough Science, based in Colorado

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Okay, on the first day of the programme we were playing around with putting the acid in the bicarbonate of soda and when you do that you get a reaction which makes the mixture froth up, and the idea is that we’re going to spray this onto a fire. And of course as it’s mainly water it’s going to put out the fire, but also the foam produced by this we hope will blanket the flames, stop the oxygen getting in, put the fire out as best we can.

So we played around. The first thing we needed to do was make the acid and so Mike B came up with this fantastic idea of heating pyrite. And so the first day I spent really helping Mike B set up the apparatus. And you roast the pyrite, it produces fumes, and if you bubble these fumes through water then it produces the acid that we need. Probably a mixture of acids but certainly a bit of sulphuric acid.

Ideally we want to get the fumes from the pyrite into the water and bubble it through, so we needed some pumping system because we didn’t think there’d be enough pressure just due to the reaction. So made up a little pump, which is just basically a large cylinder with water in it and you allow the water to fall out one end and that naturally produces a vacuum behind it. And so we used that vacuum that was created to pull air through the system, so it’s going to pull air through the apparatus mixed with the acid fumes, then bubble it through various different chambers full of water, then that water will turn acidic.

So that was the first day, and that seemed to work okay but we didn’t test it until the second day when we did the litmus test, and Mike’s results on that were fantastic, it turned the litmus red which showed that it was very acidic, so we got the result which was excellent. Then the next thing was to try putting the acid with the bicarbonate and unfortunately that was really disappointing to start with. It certainly worked but the bubbles that were produced went up and came down very quickly. So that was really disappointing. I was a bit worried at that stage.

And then Ellen suggested putting liquorice root in with the mixture, which seems a bit strange, but when we tried it it worked really, really well. What you do is you basically get the root of the liquorice plant, you grind it up in water then that water is full of the liquorice extract, and basically when that’s in the mixture the bubbles that are produced go through this liquid, agitate it, and the liquorice seems to cover the bubbles so that it produces, rather than just bubbles it produces a sort of foam which hangs around for a long time. So this is perfect for the fire extinguisher because when you spray that on the fire, not only have you got carbon dioxide from the reaction but these bubbles hang around for a long time smothering the flames, getting rid of the oxygen out of the fire.

So at the end of day two that was fantastic because we had acid that worked, bicarbonate that frothed and also we had a nice foam from the liquorice extract. So then on day three I had to get my brain together to try and make something that you could carry around like a fire extinguisher that was going to be safe to use and was going to work when we wanted it to work and not by accident. So I found that quite hard. For some reason at the end of this day I wasn’t, it wasn’t that I wasn’t inspired, I was just quite stuck for ideas.

So we tried various different things, and one idea was just simply to load the bicarbonate of soda into the acid. We have a bung on top of the cylinder and then jet the flame out, and the first time we tried this it was really funny because I didn’t expect the pressure to be very great but actually it was so great it blew the top off and foam went everywhere and I got covered in foam, which I didn’t expect at all.

So on the second one we had to make sure that the bung was really attached really firmly to the cylinder, so I used wire to wrap it on, used a slightly bigger tube so that the foam could get out easier so that the pressure wouldn’t build up too much. And that worked really well, it was really nice. We had a plastic container, like a drinks container, the acid in the bottom and then we made a little sort of umbrella to hold the bicarbonate of soda and we could fill that up from the outside, put the bung on with the tube.

And then when we wanted to use it we just simply turned it upside down, the chemicals mixed together, that produces a foam, and the liquorice extract made the foam really thick and then it flew out because of the pressure of the gas and we were able to jet it onto the flames. And we hadn’t tried it properly until we tried putting out the fire and I must admit, when we walked up to the fire and I saw there was quite a big fire, I didn’t think we were going to have enough foam to put the fire out. But it worked really well. That was just fluke I think but Mike and I were able to put the fire out completely so it was excellent.





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