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

00:00:11 August 24, 1955 on KQED Channel 9,

00:00:16 the educational station for the San Francisco Bay Area.

00:00:21 Tempest was a series of fifty-three half-hour shows pioneering a new

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

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

00:00:36 to illustrate basic, simple chemical principles.

00:00:41 The purpose was to stimulate an interest in chemistry by teenage students

00:00:46 and by adults. The talks and experiments had to be entertaining,

00:00:51 educational, and simple. Spontaneity and liveliness were key to the

00:00:56 approach. All the experiments used in the shows were designed and

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

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

00:01:11 Emeryville, and by Chevron Research, Richmond. A grant of $52,000

00:01:16 from the Ford Foundation and National Educational Television

00:01:21 permitted the filming of the first 24 shows of the series.

00:01:26 The management for the ACS consisted of Alan Nixon, section chair,

00:01:31 Fred Strauss, TV committee chair, myself as first MC,

00:01:36 and Aubrey McClellan, second MC. We four

00:01:41 constitute the core of the present committee.

00:01:46 The series was extremely popular then with KQED viewers of all

00:01:51 ages. The senior chemist committee of the California

00:01:56 section today is determined to revive Tempest for the

00:02:01 benefit of elementary schools, high schools, adult education classes,

00:02:06 ACS local sections, historical archives, TV stations,

00:02:11 and similar organizations. We believe in chemistry as a second

00:02:16 language. While basic principles have not changed,

00:02:21 practices have. 45 years ago, such simple

00:02:26 chemical demonstrations were not treated with the degree of safety

00:02:31 that they are today. Today, even such simple demonstrations

00:02:36 would be carried out with the proper regard for safety glasses,

00:02:41 shields, protective gloves, laboratory coats, and visible

00:02:46 fire extinguishers. The principle of safety first would be

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

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00:03:41 Tempest in a Test Tube, a series of

00:03:46 experiments designed to explain the mysteries of chemistry and the laws that

00:03:51 govern it. Produced by KQED San

00:03:56 Francisco.

00:04:01 In cooperation with the California section of the American

00:04:06 Chemical Society.

00:04:11 For the Educational Television and Radio Center.

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

00:04:21 Sello. Howdy. I'd like you to come with the old

00:04:26 prospector out in the desert and see what we can find.

00:04:31 Here's a good looking rock pile. Let's try

00:04:36 him out.

00:04:41 Nothing.

00:04:46 It's a strike. Uranium.

00:04:51 Well, enough of the old prospector.

00:04:56 We have found our uranium.

00:05:01 Let's take it to the laboratory and see just what we can learn about it.

00:05:06 The rock I just picked up

00:05:11 is a piece of stone that contains pitchblende, a uranium ore.

00:05:16 The instrument I used to find that rock is a Geiger counter. That was the clicking

00:05:21 noise. Really buzzes when I get close to the active

00:05:26 rock. Take the probe away and all you hear is some

00:05:31 background clicks just from the general area. A little bit contributed

00:05:36 by that rock. The property that's made use of

00:05:41 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

00:05:51 light that's invisible to the human eye, but nevertheless is there.

00:05:56 It has an activity due to this radiation. Putting the two words together, radiation activity,

00:06:01 you get radioactivity, which is the property exhibited by such minerals

00:06:06 as this piece of uranium, really uranium ore.

00:06:11 It was this property that was discovered in 1896 by Becquerel,

00:06:16 a French physicist. Quite by chance he discovered this. He had a piece of

00:06:21 photographic film in a cupboard. In this same cupboard he stored

00:06:26 a piece of uranium ore.

00:06:31 Putting the two together, you get this picture.

00:06:36 Here is the rock, which I'll handle with gloves

00:06:41 because it's a pretty hot rock, so as to speak.

00:06:46 By the way, I think I should turn this down a little bit because it's kind of noisy.

00:06:51 There. We can always turn it up to listen to the radioactivity.

00:06:56 A rock such as this, Becquerel stored in a cupboard where he had some photographic

00:07:01 plate. Well, here is a picture you get when you put this particular rock

00:07:06 on a piece of film, like so, and leave it sit, and then develop the film.

00:07:11 The picture is taken of this particular stone. In fact, you can see the line across

00:07:16 the film is the same as the line, the faint line across the rock.

00:07:21 This showed to Becquerel that there was something active

00:07:26 about the mineral that he had in his cupboard that could expose film.

00:07:31 This is one of the main properties of radioactive materials.

00:07:36 They can cause photographic film to be sensitized.

00:07:41 In the same year, one of the colleagues of Professor Becquerel,

00:07:46 a very famous woman, Madame Curie, discovered the particular,

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

00:07:56 This opened up a wide field of research about atoms and molecules

00:08:01 and about the property of radioactivity. It is from this kind of a start,

00:08:06 from this particular start, that we have learned the most about atoms and molecules

00:08:11 that we know today. Let's go on now and look at this property

00:08:16 that atoms and molecules have when they exhibit, when radioactivity is exhibited.

00:08:21 Before progressing just further about radioactivity,

00:08:26 let's examine a related property so that we can understand radioactivity

00:08:31 a little bit better. Here is an interesting little gadget.

00:08:36 It's called an electroscope. Here's how you use an electroscope.

00:08:41 Glass rod, a piece of soft facial tissue,

00:08:46 and by wiping this particular piece of paper along this piece of glass,

00:08:51 I can build up a static electrical charge.

00:08:56 Now, I'll bring this close to the electroscope.

00:09:01 Not enough charge. Try it again.

00:09:06 There. Notice that the electroscope

00:09:11 There. Notice that the two leaves

00:09:16 which were together before bringing the rod close are now apart.

00:09:21 I can bring them together by touching this electroscope with my finger.

00:09:26 The leaf collapsed. See, there are two leaves in there. As soon as I charged

00:09:31 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 It needs a little bit more rubbing to build up a bigger charge.

00:09:46 The rod crackles a little bit as I rub it this way. There, quite visible

00:09:51 that it brings it out, and it's staying there, and I ground it

00:09:56 by touching it with my finger. Rubbing the rod on the paper wipes

00:10:01 the 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

00:10:11 causes the electrons in the wire of the electroscope to run away from those on the

00:10:16 rod, since like charges in electricity repel, so that

00:10:21 the ones in the electroscope will run down toward the leaf. They'll run into both legs of this

00:10:26 Y-shaped device and cause the aluminum foil, which is

00:10:31 one of the leaves, to spring up so that it can get away with its electrons from the other piece of foil

00:10:36 with its electrons. All that occurs in one instant as I bring this close.

00:10:41 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.

00:10:51 That is, I transferred the electrons, some of them, from the rod to the electroscope so it keeps

00:10:56 the little leaf up. Let's go to the

00:11:01 next step. Here is a piece of radioactive material.

00:11:06 Actually, this is the same material that Madame Curie discovered, polonium.

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

00:11:16 I will bring this close to the electroscope. The leaf now is in this position, sort of partly open.

00:11:27 As I brought this close now, the electroscope leaf collapsed.

00:11:34 Without actually touching the electroscope, I caused the leaf to collapse.

00:11:39 This means that now I have provided some way for the electrons to be removed

00:11:44 from down in the Y-shaped portion. Just exactly what happened.

00:11:52 The electrons were down on the leaves. When the piece of polonium was brought

00:11:57 close to the tip of the electroscope, the air around it, the electroscope, was changed

00:12:02 so that it could conduct electricity. It was what we call ionized,

00:12:07 made into charged particles. These charged particles were then attracted

00:12:12 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

00:12:22 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 the chart. The ionization of air.

00:12:32 This means forming ions. Ions are little, are atoms,

00:12:37 or groups of atoms which have an electrical charge. In the case of nitrogen,

00:12:42 N2, the symbol, nitrogen became a positively charged ion because

00:12:47 it lost an electron due to the polonium radiation

00:12:52 breaking the nitrogen electrons away. The same thing happened to oxygen.

00:12:57 These two charged particles were then attracted over to the electroscope and

00:13:02 resulted in neutralizing the electrons which were put on the electroscope

00:13:07 originally by the glass rod. Well, the whole purpose of this particular

00:13:12 experiment is to show that by using an electroscope, one can

00:13:17 determine whether a particular material is radioactive or not. Because if a

00:13:22 material is radioactive, it will ionize the air and the charge will leak off from the electroscope.

00:13:27 This type of instrument, a little bit more refined,

00:13:32 was practically the only thing that was used by the early research people

00:13:37 in radiation, in radioactivity. They built very fine such electroscopes

00:13:42 and made lots of measurements in those days that are quite true even today.

00:13:47 Let's go on then and look at this property of radioactivity just a little bit further.

00:13:52 We now know that the second property of something that's radioactive

00:13:57 is that it can ionize air. The first was it can expose film. The second is

00:14:02 that it can ionize air. Let's look a little further at still a third property,

00:14:07 that which is exemplified by the Geiger counter.

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

00:14:22 Turn it on, let it warm up a little bit.

00:14:27 The probe of the Geiger counter,

00:14:32 which is connected to the meter, actually has in it a little mica

00:14:37 window.

00:14:42 This mica window picks up radioactivity,

00:14:47 which is then reflected in the meter.

00:14:52 We need a little volume on this to make it work.

00:14:57 There we go. We also need a little power, you see,

00:15:02 since this is electrically operated. Now you can begin to hear the Geiger counter.

00:15:07 This comes from the samples of uranium ore here,

00:15:12 plus some of the natural background that exists around us all the time.

00:15:17 Let me just clamp this probe in so I won't break it. The thin window

00:15:22 is just a very, very thin wafer. One merely has to touch it with a finger in order to break it.

00:15:27 If you wanted to break it, that is. Now I talked about having hot rocks

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

00:15:37 Radioactively warm.

00:15:42 The term hot is, of course, used quite a bit in talking about radioactivity because

00:15:47 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. It has a scale on it which can pick off

00:15:57 various degrees of counting. The lowest part counts up to 300

00:16:02 counts per minute and 1,000 and 3,000 and so forth. I'll keep it over on the 30,000

00:16:07 side. It means full scale is 30,000 counts per minute. Each little click is one

00:16:12 count. Let's bring over this polonium that was

00:16:17 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

00:16:27 background that it doesn't even lift the needle from the pin.

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

00:16:37 In fact, it's so fast, counting

00:16:42 so fast, it is just jamming. All you get is a steady buzz.

00:16:47 Notice a peculiar thing. Nothing happens if I'm

00:16:52 more than an inch away from the probe of the Geiger counter, but as soon as I get to within about an inch,

00:16:57 I immediately get enough radiation to

00:17:02 push the needle right off scale, 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

00:17:12 or so from the Geiger counter, nothing will register, just background. This tells

00:17:17 us something about the particular kind of radiation. We'll get to that in a moment.

00:17:22 Look what happens now. I bring the polonium source up.

00:17:27 Very active. Needle off the pin.

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

00:17:37 The paper is

00:17:42 enough to stop the radiation. All you get now is a sort of a general background.

00:17:47 Jammed.

00:17:52 Nothing. Background count.

00:17:57 This shows that polonium gives off a particular kind of radiation, which we'll get to in just a

00:18:02 moment. By the way, you might have noticed when I first came up to this

00:18:07 instrument that I had to turn the strip over. This is a piece of brass strip which has just been coated on one side

00:18:12 with polonium. There's the active side. This is the inactive side.

00:18:17 Needless to say, it shows that the polonium doesn't go through the piece of brass.

00:18:22 I'll put this back. That showed one kind of radioactivity.

00:18:27 Let's try still another. Here's a little pellet. Now this particular pellet

00:18:32 I can handle because it's encased in a shield.

00:18:37 Pretty active.

00:18:42 Not as active as the polonium, but

00:18:47 about 20,000 counts per minute.

00:18:52 Let's try my piece of paper on this one.

00:18:57 Paper. Source.

00:19:02 No effect.

00:19:07 Now let's try a quarter inch piece of lead. A quarter inch thick piece of lead.

00:19:12 Here's the source. Active.

00:19:17 Nothing. Just background. Active.

00:19:22 Just a little bit. Less than 500 counts per minute.

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

00:19:32 to stop it from the polonium. It took a quarter inch thick piece of lead to stop this

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

00:19:42 The Geiger counter operates on a similar principle to that which was illustrated

00:19:47 in the case of the electroscope. In this probe is a chamber

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

00:19:57 wire. As the radiation goes into the

00:20:02 probe, shoots into this chamber of gas, the gas is ionized just in the same way

00:20:07 that I pointed out the air was ionized around the electroscope. Electrons are kicked out

00:20:12 in this ionization of the gas inside. These electrons kick out more

00:20:17 electrons. There's a multiplication effect. And all of the electrons

00:20:22 inside, well not every one, but most of them then, get over onto the

00:20:27 charged wire in the center of the probe. This causes an electrical current to flow

00:20:32 registering on the needle in the meter.

00:20:37 Well, we've now seen the other property that was illustrated by the radioactive materials.

00:20:42 Exposure of film, ionization of air, now ionization of gas in the

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

00:20:52 Well, what then is radioactivity? Radioactivity is the breaking

00:20:57 apart spontaneously, that is by itself, of certain elements

00:21:02 like radium or uranium or polonium. In nature, quite by themselves,

00:21:07 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

00:21:22 three, which we pointed out by the Geiger counter. Let's write them down.

00:21:27 The chemist has been very tricky here, he just writes down by using Greek letters

00:21:32 the three kinds of radiation that there are in natural radioactivity.

00:21:37 Alpha radiation, symbol alpha, Greek letter.

00:21:42 Beta radiation, I'm already using the

00:21:47 Greek letter first. Beta radiation, symbol beta.

00:21:52 And gamma radiation, symbol gamma.

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

00:22:02 Alpha radiation, alpha rays, are simply helium nuclei.

00:22:07 Pieces of a helium atom.

00:22:12 EI.

00:22:17 Beta radiation are streams of electrons.

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

00:22:27 invisible. In the case of the Geiger counter, the alpha radiation

00:22:32 was stopped by the paper, as we showed, but this wasn't enough to stop the beta radiation

00:22:37 and the gamma radiation. For that it took a little piece of lead.

00:22:42 This radiation then points to the fact that there are various parts to an atom.

00:22:47 An atom then looks something like this. There is a center called the nucleus

00:22:52 with electrons spinning around on the outside, sort of a

00:22:57 miniature solar system. And to date we have identified

00:23:02 in chemistry and physics several parts to an atom. Let me just

00:23:07 quickly make a list of the parts of the atom that we now know. Protons.

00:23:12 Electrons.

00:23:17 Neutrons. These are the main parts.

00:23:22 In addition to those, there are several more. Just to give them their names.

00:23:27 Positrons. Neutrinos.

00:23:32 Mesons. I'll write this up here.

00:23:37 There are three kinds of these now known. Then we have two others

00:23:42 which are rare. Antiprotons and

00:23:47 antineutrons. Well, the ones that are really important are these three.

00:23:52 They're located, the two protons and neutrons are located in the nucleus of an atom.

00:23:57 Electrons are around the outside. The chemist is concerned with these outer electrons.

00:24:02 Let's go on then and look at yet another very interesting way

00:24:07 of actually seeing some radioactivity occur. We saw a meter.

00:24:12 But we didn't see the radioactivity. We saw a reading on the meter. Here is a device

00:24:17 called a cloud chamber. I'll turn the light on.

00:24:22 The whirring noise is the fan which is cooling this sharp beam

00:24:27 of light, of the projector putting out the light. The fan is cooling it.

00:24:32 Now, in the center of this dish, well in the dish

00:24:37 there is a liquid. 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

00:24:47 some of the action which is occurring. Notice the

00:24:52 sharp streaks of light that shoot across the cloud chamber.

00:24:57 Each one of those streaks is a radioactive, is a particle resulting from

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

00:25:07 The long straight tracks are the alphas

00:25:12 and the even longer, rather winding, wavery tracks are the electrons

00:25:17 or the betas. Here's how a cloud chamber works.

00:25:22 You're familiar with the fact, I'm sure, that at the center

00:25:27 of a raindrop is usually a particle of dust. This comes about by

00:25:32 the virtue of the fact that water vapor can accumulate under certain conditions

00:25:37 when it's considered to be super saturated in air, let's say.

00:25:42 Water vapor can accumulate around a dust particle and form a little drop.

00:25:47 In this chamber we have not water, but methyl alcohol. The chamber is full

00:25:52 of vapors of methyl alcohol. The vapors are all just about ready to condense into

00:25:57 a fog, but they need something to get them started. A piece of dust would do it. In this case

00:26:02 the alpha particles do it. So every time an alpha particle charges across the chamber

00:26:07 it collects fog along its track. That's the little shadowy streak you see.

00:26:12 This will go on and

00:26:17 show the radiation as long as that source, which happens to be radium, is not used up,

00:26:22 which will last for many, many years. Let's go on now a little further

00:26:27 and look at the various uses of radioactivity.

00:26:32 Here's one right here. Oh, by the way,

00:26:37 while I have it here, here is a picture which was taken of a cloud

00:26:42 chamber much more elaborate than the one I just showed you. A very, a big one

00:26:47 which can do a much finer job than the one I did show you. The faint

00:26:52 streaks going down the paper are actual pictures of these fog tracks.

00:26:57 The kinky lines resulting are the lines of the alpha particles and

00:27:02 betas, the same as you saw in the cloud chamber. This is the kind of picture that is taken by

00:27:07 people doing research in radiation chemistry or in radioactivity.

00:27:12 This was given to us by the University of California Radiation Laboratory, where they have tremendous

00:27:17 cloud chambers, having pictures taken of them all the time.

00:27:22 By the way, I wanted to mention that this matter of a piece of

00:27:27 radioactive material being able to expose photographic film is made use of

00:27:32 in the safety considerations of radioactivity. Here is what a

00:27:37 chemist studying radioactivity would call a film badge. This little thing contains a piece

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

00:27:47 come near some radiation, why, it exposes the film. 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.

00:28:07 Nuclear fission or a chain reaction.

00:28:12 Let's just run through this chart. Here is a schematic picture

00:28:17 of a kind of uranium, uranium-235, one of the isotopes of uranium.

00:28:22 We'll have more to say about isotopes in a later talk.

00:28:27 A neutron, pictured by this black dot,

00:28:32 will collide or can collide with a uranium-235 nucleus

00:28:37 and cause that nucleus to split into two pieces, almost equal halves.

00:28:42 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

00:28:57 neutrons are shown on this schematic diagram. This isn't exactly what happens, but it's this type of thing.

00:29:02 From one neutron hitting uranium-235 nucleus, we now have a multiplication up to four.

00:29:07 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.

00:29:22 However, in a practical sense, this can be built into the form of a reactor.

00:29:27 Uranium-235, fuel elements, reacting all the time.

00:29:32 To control the reaction, graphite rods can be dropped in between,

00:29:37 just in the same way that I used paper to stop alpha radiation.

00:29:42 The whole thing is encased in a thick concrete shield to protect the users.

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

00:29:52 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,

00:30:07 you can map out the area of the goiter and show where the surgery should occur.

00:30:12 Let's talk a little bit about radioactivity.

00:30:15 The old prospector discovered a piece of uranium.

00:30:18 He used a Geiger counter to discover this.

00:30:21 This made use of one of the properties of a piece of radioactive material.

00:30:26 We define the term radioactivity, meaning radiation activity.

00:30:32 A mysterious kind of light invisible to the eye.

00:30:38 Hence, radiation activity or radioactivity.

00:30:42 We showed that one of the things a radioactive material could do is ionize air,

00:30:47 knock the electrons from nitrogen and oxygen molecules,

00:30:51 make them into ions, which are positively charged particles,

00:30:55 and they could then discharge a previously charged electroscope,

00:30:59 which we showed in our second experiment.

00:31:03 This property was made use of, as I say, in the Geiger counter,

00:31:06 which is an instrument for measuring radioactivity.

00:31:09 We then showed that there are various kinds of radioactivity,

00:31:12 one which was stopped by paper. This was the alpha radiation.

00:31:16 The other which was stopped by a thickness of lead.

00:31:20 This was the beta and gamma radiation.

00:31:24 We then looked at an example of radiation occurring instantly at the moment

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

00:31:34 These were tearing through the cloud chamber, leaving fog tracks.

00:31:38 Finally, we mentioned the practical use of radioactivity in nuclear reactors and in tracers.

00:31:44 Thank you.

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00:32:30 This is National Educational Television.