00:00:01 Hello, I am Harry Sello. It is my pleasure to introduce

00:00:06 Tempest in a Test Tube, a television show which made its debut August 24, 1955

00:00:13 on KQED Channel 9, the educational station for the San Francisco Bay Area.

00:00:20 Tempest was a series of fifty-three half-hour shows pioneering a new approach

00:00:26 in which I, as lecture demonstrator, gave live, unrehearsed presentations

00:00:31 of a series of chemical experiments. These were designed to illustrate

00:00:36 basic, simple chemical principles. The purpose was to stimulate an interest

00:00:42 in chemistry by teenage students and by adults. The talks and experiments

00:00:49 had to be entertaining, educational, and simple. Spontaneity and liveliness

00:00:55 were key to the approach. All the experiments used in the shows were designed

00:01:00 and constructed by members of the California section of the American Chemical Society.

00:01:06 The participants were employed by the Shell Development Company, Emeryville,

00:01:11 and by Chevron Research, Richmond. A grant of $52,000 from the Ford Foundation

00:01:18 and National Educational Television permitted the filming of the first 24 shows

00:01:23 of the series. The management for the ACS consisted of Alan Nixon, section chair,

00:01:30 Fred Strauss, TV committee chair, myself as first emcee, and Aubrey McClellan,

00:01:37 second emcee. We four constitute the core of the present committee.

00:01:44 The series was extremely popular then with KQED viewers of all ages.

00:01:52 The senior chemist committee of the California section today is determined

00:01:58 to revive Tempest for the benefit of elementary schools, high schools,

00:02:03 adult education classes, ACS local sections, historical archives, TV stations,

00:02:10 and similar organizations. We believe in chemistry as a second language.

00:02:17 While basic principles have not changed, practices have.

00:02:23 Forty-five years ago, such simple chemical demonstrations were not treated

00:02:27 with the degree of safety considerations that they are today.

00:02:32 Today, even such simple demonstrations would be carried out with the proper regard

00:02:38 for safety glasses, shields, protective gloves, laboratory coats,

00:02:44 and visible fire extinguishers. The principle of safety first would be explicitly present

00:02:51 as part and parcel of a modern Tempest in a Test Tube.

00:03:14 Tempest in a Test Tube.

00:03:43 Tempest in a Test Tube, a series of experiments designed to explain the mysteries

00:03:48 of chemistry and the laws that govern it.

00:03:53 Produced by KQED San Francisco, in cooperation with the California section

00:04:04 of the American Chemical Society, for the Educational Television and Radio Center.

00:04:16 And now let's go to our laboratory and meet Dr. Harry Sello.

00:04:22 Howdy. I'd like you to come with the old prospector out in the desert and see what we can find.

00:04:32 Here's a good-looking rock pile. Let's try him out.

00:04:37 Uh-uh. Nothing. Uh-uh.

00:04:47 It's a strike. Uranium.

00:04:54 Well, enough of the old prospector.

00:04:58 We have found our uranium. Let's take it to the laboratory and see just what we can learn about it.

00:05:07 The rock I just picked up is a piece of stone that contains pitchblende, a uranium ore.

00:05:15 The instrument I used to find that rock is a Geiger counter. That was the clicking noise.

00:05:23 It really buzzes when I get close to the active rock.

00:05:27 Take the probe away and all you hear is some background clicks just from the general area.

00:05:34 A little bit contributed by that rock.

00:05:39 The property that's made use of here to find the rock is called radioactivity.

00:05:46 You see, what the rock does is give off a sort of a radiation, a kind of light that's invisible to the human eye, but nevertheless is there.

00:05:55 It has an activity due to this radiation. Putting the two words together, radiation activity, you get radioactivity,

00:06:02 which is the property exhibited by such minerals as this piece of uranium, really uranium ore.

00:06:11 It was this property that was discovered in 1896 by Becquerel, a French physicist.

00:06:17 Quite by chance he discovered this. He had a piece of photographic film in a cupboard.

00:06:22 In the same cupboard he stored a piece of uranium ore.

00:06:32 Putting the two together, you get this picture.

00:06:38 Here is the rock, which I'll handle with gloves, because it's a pretty hot rock, so as to speak.

00:06:48 By the way, I think I should turn this down a little bit because it's kind of noisy.

00:06:55 There. We can always turn it up to listen to the radioactivity.

00:07:00 A rock such as this, Becquerel stored in a cupboard where he had some photographic plate.

00:07:05 Well, here is a picture you get when you put this particular rock on a piece of film, like so, and leave it sit,

00:07:13 and then develop the film. The picture is taken of this particular stone.

00:07:17 In fact, you can see the line across the film is the same as the line, the faint line across the rock.

00:07:27 This showed to Becquerel that there was something active about the mineral that he had in his cupboard that could expose film.

00:07:34 This is one of the main properties of radioactive materials.

00:07:38 They can cause photographic film to be sensitized.

00:07:44 In the same year, one of the colleagues of Professor Becquerel, a very famous woman, Madam Curie,

00:07:51 discovered the first radioactive element, polonium, and later that same year, radium.

00:08:00 This opened up a wide field of research about atoms, molecules, and about the property of radioactivity.

00:08:08 It is from this kind of a start, from this particular start, that we have learned the most about atoms and molecules that we know today.

00:08:17 Let's go on now and look at this property that atoms and molecules have when they exhibit, when radioactivity is exhibited.

00:08:28 Before progressing just further about radioactivity, let's examine a related property so that we can understand radioactivity a little bit better.

00:08:38 Here is an interesting little gadget. It's called an electroscope.

00:08:44 Here's how you use an electroscope.

00:08:47 A glass rod, a piece of soft facial tissue, and by wiping this particular piece of paper along this piece of glass, I can build up a static electrical charge.

00:09:01 Now, I'll bring this close to the electroscope.

00:09:06 Not enough charge. Try it again.

00:09:14 There. Notice that the two leaves, which were together before bringing the rod close, are now apart.

00:09:23 I can bring them together by touching this electroscope with my finger.

00:09:28 The leaf collapsed.

00:09:30 See, there are two leaves in there. As soon as I charged the electroscope, one of them flipped up just like I'm doing with my fingers.

00:09:36 Let's repeat that just to see it happen.

00:09:41 Needs a little bit more rubbing to build up a bigger charge.

00:09:44 This rod crackles a little bit as I rub it this way.

00:09:47 There. Quite visible that it brings it out, and it's staying there, and I ground it by touching it with my finger.

00:09:57 Rubbing the rod on the paper wipes electrons from the paper onto the glass rod, those parts of an atom.

00:10:06 Bringing this rod with its electrons close to the electroscope causes the electrons in the wire of the electroscope to run away from those on the rod,

00:10:16 since like charges in electricity repel, so that the ones in the electroscope will run down toward the leaf.

00:10:23 They'll run into both legs of this Y-shaped device and cause the aluminum foil, which is one of the leaves, to spring up,

00:10:31 so that it can get away with its electrons from the other piece of foil with its electrons.

00:10:37 All that occurs in one instant as I bring this close.

00:10:40 Now let's see if I can put a charge on this electroscope and keep it there.

00:10:46 There. This time I touched the electroscope.

00:10:50 That is, I transferred the electrons, some of them, from the rod to the electroscope, so it keeps the little leaf up.

00:10:59 Let's go to the next step.

00:11:02 Here is a piece of radioactive material.

00:11:05 Actually, this is the same material that Madame Curie discovered, polonium.

00:11:11 It has been plated onto a brass strip of metal.

00:11:15 I will bring this close to the electroscope.

00:11:17 The leaf now is in this position, sort of partly open.

00:11:21 As I brought this close now, the electroscope leaf collapsed.

00:11:32 Without actually touching the electroscope, I caused the leaf to collapse.

00:11:37 This means that now I have provided some way for the electrons to be removed from down in the Y-shaped portion.

00:11:46 Just exactly what happened.

00:11:51 The electrons were down on the leaves.

00:11:55 When the piece of polonium was brought close to the tip of the electroscope, the air around it, the electroscope, was changed so that it could conduct electricity.

00:12:04 It was what we call ionized, made into charged particles.

00:12:09 These charged particles were then attracted over to the electroscope, which itself was charged in the opposite way.

00:12:17 A minus charge in the electroscope attracted the positive charges of these air molecules and neutralized each other so that the electroscope leaves could collapse.

00:12:27 Here is the way the chemist looks at it in a chart.

00:12:30 The ionization of air.

00:12:32 This means forming ions.

00:12:34 Ions are little, are atoms or groups of atoms which have an electrical charge.

00:12:39 In the case of nitrogen, N2, the symbol, nitrogen became a positively charged ion because it lost an electron due to the polonium radiation breaking the nitrogen electrons away.

00:12:53 The same thing happened to oxygen.

00:12:56 These two charged particles were then attracted over to the electroscope and resulted in neutralizing the electrons which were put on the electroscope originally by the glass rod.

00:13:08 Well, the whole purpose of this particular experiment is to show that by using an electroscope, one can determine whether a particular material is radioactive or not.

00:13:20 Because if a material is radioactive, we will ionize the air and the charge will leak off from the electroscope.

00:13:26 Leak off the electroscope, really.

00:13:29 This type of instrument, a little bit more refined, was practically the only thing that was used by the early research people in radiation, in radioactivity.

00:13:39 They built very fine such electroscopes and made lots of measurements in those days that are quite true even today.

00:13:48 Let's go on then and look at this property of radioactivity just a little bit further.

00:13:53 We now know that the second property of something that's radioactive is that it can ionize air.

00:14:00 The first was it can expose film.

00:14:02 The second is that it can ionize air.

00:14:04 Let's look a little further at still a third property, that which is exemplified by the Geiger counter.

00:14:12 For this, I'll leave my counter over here.

00:14:24 Turn it on, let it warm up a little bit.

00:14:31 The probe of the Geiger counter, which is connected to the meter, actually has in it a little mica window.

00:14:43 This mica window picks up radioactivity, which is then reflected in the meter.

00:14:48 Now, we'll need a little volume on this to make it work.

00:14:56 There we go.

00:14:58 We also need a little power, you see, since this is electrically operated.

00:15:03 Now you can begin to hear the Geiger counter.

00:15:06 This comes from the samples of uranium ore here, plus some of the natural background that exists around us all the time.

00:15:16 Let me just clamp this probe in so I won't break it.

00:15:20 This thin window is just a very, very thin wafer.

00:15:23 One merely has to touch it with a finger in order to break it, if you wanted to break it, that is.

00:15:29 Now I talked about having hot rocks over there.

00:15:32 It's also kind of warm thermally, as well as radioactivity, radioactively warm.

00:15:41 The term hot is, of course, used quite a bit in radio, in talking about radioactivity,

00:15:46 because we talk about things being hot in a radioactive sense as well as being hot in a temperature sense.

00:15:52 Now the Geiger counter is ready to operate.

00:15:54 It has a scale on it which can pick off various degrees of counting.

00:15:59 The lowest part counts up to 300 counts per minute and 1,000 and 3,000 and so forth.

00:16:05 I'll keep it over on the 30,000 side.

00:16:07 It means full scale is 30,000 counts per minute.

00:16:10 Each little click is one count.

00:16:14 Let's bring over this polonium that was used on the electroscope and see what the Geiger counter says about it.

00:16:22 Now the clicking rate is so low now in background that it doesn't even lift the needle from the pin.

00:16:32 I'll bring the polonium up.

00:16:38 In fact, it's so fast, counting so fast, it is just jamming.

00:16:41 All you get is a steady buzz.

00:16:45 Notice a peculiar thing.

00:16:47 Notice a peculiar thing.

00:16:50 Nothing happens if I'm more than an inch away from the probe of the Geiger counter,

00:16:54 but as soon as I get to within about an inch,

00:16:57 I immediately get enough radiation to push the needle right off scale,

00:17:03 way more than 30,000 counts per minute.

00:17:07 What this shows is that if this particular radiation source is more than an inch away or so from the Geiger counter,

00:17:13 nothing will register, just background.

00:17:15 This tells us something about the particular kind of radiation.

00:17:18 We'll get to that in a moment.

00:17:21 Look what happens now.

00:17:23 I bring the polonium source up.

00:17:27 Very active.

00:17:30 Needle off the pin.

00:17:32 I will now slip this thin sheet of paper between the polonium and the Geiger counter.

00:17:40 The paper is enough to stop the radiation.

00:17:43 All you get now is a sort of a general background.

00:17:48 Jammed.

00:17:51 Nothing.

00:17:52 Background counts.

00:17:56 This shows that polonium gives off a particular kind of radiation,

00:18:00 which we'll get to in just a moment.

00:18:02 By the way, you might have noticed when I first came up to this instrument that I had to turn the strip over.

00:18:08 This is a piece of brass strip which has just been coated on one side with polonium.

00:18:13 There's the active side.

00:18:14 This is the inactive side.

00:18:16 Needless to say, it shows that the polonium doesn't go through the piece of brass.

00:18:20 I'll put this back.

00:18:23 That showed one kind of radioactivity.

00:18:28 Let's try still another.

00:18:29 Here's a little pellet.

00:18:30 Now, this particular pellet I can handle because it's encased in a shield.

00:18:39 Pretty active.

00:18:41 Not as active as the polonium, but...

00:18:49 About 20,000 counts per minute.

00:18:54 Let's try my piece of paper on this one.

00:18:56 Paper.

00:18:57 Source.

00:19:03 No effect.

00:19:06 Now, let's try a quarter inch piece of lead.

00:19:10 A quarter inch thick piece of lead.

00:19:13 Here's the source.

00:19:14 Active.

00:19:16 Nothing.

00:19:17 Just background.

00:19:18 Active.

00:19:22 Just a little bit.

00:19:24 Less than 500 counts per minute.

00:19:27 Paper was not enough to stop the radiation from this source where it was enough to stop it from the polonium.

00:19:33 It took a quarter inch thick piece of lead to stop this particular radiation.

00:19:37 This tells us that there is still another kind of radiation.

00:19:40 The Geiger counter operates on a similar principle to that which was illustrated in the case of the electroscope.

00:19:48 In this probe is a chamber full of gas.

00:19:52 Down the center of this chamber is a highly charged wire.

00:19:58 As the radiation goes into the probe, shoots into this chamber of gas,

00:20:03 the gas is ionized just in the same way that I pointed out the air was ionized around the electroscope.

00:20:09 Electrons are kicked out in this ionization of the gas inside.

00:20:15 These electrons kick out more electrons.

00:20:17 There's a multiplication effect.

00:20:19 And all of the electrons inside, well not every one, but most of them then,

00:20:25 get over onto the charged wire in the center of the probe.

00:20:28 This causes an electrical current to flow, registering on the needle in the meter.

00:20:36 Well, we've now seen the other property that was illustrated by the radioactive materials.

00:20:41 Exposure of film, ionization of air, now ionization of gas in the Geiger counter,

00:20:47 and then record of this particular ionization.

00:20:51 Well, what then is radioactivity?

00:20:54 Radioactivity is the breaking apart spontaneously, that is by itself, of certain elements,

00:21:01 like radium or uranium or polonium.

00:21:04 In nature, quite by themselves, as they occur, they are constantly disintegrating, breaking apart.

00:21:12 This is called natural radioactivity, as it occurs in nature, natural.

00:21:17 The radiation consists of several kinds, actually three, which we pointed out by the Geiger counter.

00:21:25 Let's write them down.

00:21:26 The chemist has been very tricky here, he just writes down by using Greek letters

00:21:31 the three kinds of radiation that there are in natural radioactivity.

00:21:35 Alpha radiation, symbol alpha, Greek letter.

00:21:41 Beta radiation, I'm already using the Greek letter first.

00:21:48 Beta radiation, symbol beta, and gamma radiation, symbol gamma.

00:21:57 The three kinds of radiation in natural radioactivity.

00:22:00 Alpha radiation, alpha rays, are simply helium nuclei, pieces of a helium atom.

00:22:12 EI.

00:22:15 Betas, beta radiation, are streams of electrons.

00:22:21 And gamma radiation are just rays, very similar to light, only invisible.

00:22:28 In the case of the Geiger counter, the alpha radiation was stopped by the paper, as we showed.

00:22:34 But this wasn't enough to stop the beta radiation and the gamma radiation.

00:22:37 For that it took the little piece of lead.

00:22:41 This radiation, then, points to the fact that there are various parts to an atom.

00:22:46 An atom, then, looks something like this.

00:22:49 There is a center called the nucleus with electrons spinning around on the outside,

00:22:55 sort of a miniature solar system.

00:22:58 And to date we have identified, in chemistry and physics, several parts to an atom.

00:23:04 Let me just quickly make a list of the parts of the atom that we now know.

00:23:09 Protons.

00:23:12 Electrons.

00:23:16 Neutrons.

00:23:19 These are the main parts.

00:23:21 In addition to those, there are several more.

00:23:23 Just to give them their names.

00:23:25 Positrons.

00:23:29 Neutrinos.

00:23:34 Mesons.

00:23:35 I'll write this up here.

00:23:37 There are three kinds of these now known.

00:23:39 Then we have two others, which are rare.

00:23:42 Antiprotons.

00:23:45 And antineutrons.

00:23:48 Well, the ones that are really important are these three.

00:23:51 They're located, the two protons and neutrons are located in the nucleus of an atom.

00:23:56 Electrons are around the outside.

00:23:58 The chemist is concerned with these outer electrons.

00:24:01 Let's go on then and look at yet another very interesting way of actually seeing some radioactivity occur.

00:24:08 We saw a meter, but we didn't see the radioactivity.

00:24:12 We saw a reading on the meter.

00:24:14 Here is a device called a cloud chamber.

00:24:17 I'll turn the light on.

00:24:20 The whirring noise is the fan, which is cooling this sharp beam of light of the projector.

00:24:28 Putting out the light, the fan is cooling it.

00:24:31 Now, in the center of this dish, well, in the dish there is a liquid.

00:24:38 The liquid vaporizes rather readily.

00:24:42 Now you can begin to see, I'll interrupt this for a moment, you can begin to see some of the action which is occurring.

00:24:49 Notice the sharp streaks of light that shoot across the cloud chamber.

00:24:56 Each one of those streaks is a radioactive, is a particle resulting from radioactive decay.

00:25:02 Either an alpha particle or a beta particle.

00:25:08 The long, straight tracks are the alphas, and the even longer, rather winding, wavery tracks are the electrons, or the betas.

00:25:18 Here's how a cloud chamber works.

00:25:21 You're familiar with the fact, I'm sure, that in a raindrop, at the center of a raindrop is usually a particle of dust.

00:25:27 This comes about by the virtue of the fact that water vapor can accumulate under certain conditions.

00:25:36 When it's considered to be super saturated in air, let's say, water vapor can accumulate around a dust particle and form a little drop.

00:25:44 In this chamber we have not water, but methyl alcohol.

00:25:48 The chamber is full of vapors of methyl alcohol.

00:25:52 The vapors are all just about ready to condense into a fog, but they need something to get them started.

00:25:56 A piece of dust would do it.

00:25:58 In this case, the alpha particles do it.

00:26:01 So every time an alpha particle charges across the chamber, it collects fog along its track.

00:26:07 That's the little shadowy streak you see.

00:26:10 This will go on and show the radiation as long as that source, which happens to be radium, is not used up, which will last for many, many years.

00:26:22 Let's go on now a little further and look at the various uses of radioactivity.

00:26:30 Here's one right here.

00:26:32 Here's one right here.

00:26:35 Oh, by the way, while I have it here, here is a picture which was taken of a cloud chamber much more elaborate than the one I just showed you.

00:26:44 A very, a big one, which can do a much finer job than the one I did show you.

00:26:50 The faint streaks going down the paper are actual pictures of these fog tracks.

00:26:56 The kinky lines resulting are the lines of the alpha particles and betas, the same as you saw in the cloud chamber.

00:27:04 This is the kind of picture that is taken by people doing research in radiation chemistry or in radioactivity.

00:27:11 This was given to us by the University of California Radiation Laboratory, where they have tremendous cloud chambers, having pictures taken of them all the time.

00:27:21 By the way, I wanted to mention that this matter of a piece of radioactive material being able to expose photographic film is made use of in the safety considerations of radioactivity.

00:27:34 Here is what a chemist studying radioactivity would call a film badge.

00:27:40 This little thing contains a piece of film.

00:27:42 When working around radioactivity, you wear this all the time.

00:27:46 Every time you come near some radiation, why, it exposes the film.

00:27:49 At the end of each week, this may be then processed.

00:27:52 Then you can have a measure of how much radioactivity you ran into.

00:27:57 We were talking then, going to talk then about the uses of radioactivity as well.

00:28:02 Here is one of the most striking uses of radioactivity that many of you probably know about.

00:28:08 Nuclear fission or a chain reaction.

00:28:13 Let's just run through this chart.

00:28:15 Here is a schematic picture of a kind of uranium, uranium-235, one of the isotopes of uranium.

00:28:23 We'll have more to say about isotopes in a later talk.

00:28:26 A neutron, pictured by this black dot, will collide or can collide with a uranium-235 nucleus and cause that nucleus to split into two pieces, almost equal halves.

00:28:43 At the same time, additional neutrons are given off.

00:28:47 These two then go on and split two other nuclei.

00:28:52 These are the bigger pieces given off, and four neutrons are shown on the schematic diagram.

00:28:58 This isn't exactly what happens, but it's this type of thing.

00:29:01 So from one neutron hitting uranium-235 nucleus, we now have a multiplication up to four.

00:29:08 The whole result then can be multiplied many, many millions of times.

00:29:12 Since energy is given off every time this splits, you get a tremendous amount of energy.

00:29:17 This is what an atom bomb, a fission bomb, will do.

00:29:21 However, in a practical sense, this can be built into the form of a reactor.

00:29:26 Uranium-235, fuel elements, reacting all the time.

00:29:31 To control the reaction, graphite rods can be dropped in between, just in the same way that I used paper to stop alpha radiation.

00:29:39 The whole thing is encased in a thick concrete shield to protect the users.

00:29:43 This is a practical use of radioactivity.

00:29:47 Still another is in the use of tracers in medical uses.

00:29:50 For example, by making radioactive iodine, it's possible for a doctor to map out the area of a goiter,

00:29:57 if a person has a goiter in a thyroid gland and a growth on the thyroid gland.

00:30:02 By using a Geiger counter and radioactive iodine fed to the patient,

00:30:05 you can map out the area of the goiter and show where the surgery should occur.

00:30:09 Well, let's look and see what we've learned about radioactivity.

00:30:14 The old prospector discovered a piece of uranium.

00:30:17 He used a Geiger counter to discover this.

00:30:19 This made use of one of the properties of a piece of radioactive material.

00:30:24 We defined the term radioactivity, meaning radiation activity,

00:30:31 a mysterious kind of light invisible to the eye, active, hence radiation activity or radioactivity.

00:30:41 We showed that one of the things a radioactive material could do is ionize air,

00:30:46 knock the electrons from nitrogen and oxygen molecules,

00:30:50 make them into ions, which are positively charged particles,

00:30:54 and they could then discharge a previously charged electroscope,

00:30:58 which we showed in our second experiment.

00:31:02 This property was made use of, as I say, in the Geiger counter,

00:31:05 which is an instrument for measuring radioactivity.

00:31:08 We then showed that there are various kinds of radioactivity,

00:31:11 one which was stopped by paper, this was the alpha radiation,

00:31:15 the other which was stopped by a thickness of lead.

00:31:19 This was the beta and gamma radiation.

00:31:23 We then looked at an example of radiation occurring instantly at the moment in the cloud chamber

00:31:30 where a piece of radium was sending off alpha and beta particles.

00:31:33 These were tearing through a cloud chamber, leaving fog tracks.

00:31:37 Finally, we mentioned the practical use of radioactivity in nuclear reactors and in tracers.

00:31:44 Thank you.

00:32:14 This is National Educational Television.