00:00:00 Hello, I am Harry Sello. It is my pleasure to introduce Tempest in a Test Tube, a television show which made its debut August 24, 1955, on KQED, Channel 9, the educational station for the San Francisco Bay Area.

00:00:20 Tempest was a series of 53 half-hour shows pioneering a new approach in which I, as lecture demonstrator, gave live, unrehearsed presentations of a series of chemical experiments.

00:00:35 These were designed to illustrate basic, simple chemical principles. The purpose was to stimulate an interest in chemistry by teenage students and by adults.

00:00:48 The talks and experiments had to be entertaining, educational, and simple. Spontaneity and liveliness were key to the approach.

00:00:58 All the experiments used in the shows were designed and constructed by members of the California section of the American Chemical Society.

00:01:07 The participants were employed by the Shell Development Company, Emeryville, and by Chevron Research, Richmond.

00:01:15 A grant of $52,000 from the Ford Foundation and National Educational Television 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, Fred Strauss, TV committee chair, myself as first emcee, and Aubrey McClellan, second emcee.

00:01:40 We four constitute the core of the present committee. The series was extremely popular then with KQED viewers of all ages.

00:01:53 The senior chemist committee of the California section today is determined to revive Tempest for the benefit of elementary schools, high schools, adult education classes,

00:02:06 ACS local sections, historical archives, TV stations, and similar organizations. We believe in chemistry as a second language.

00:02:18 While basic principles have not changed, practices have. 45 years ago, such simple chemical demonstrations were not treated with the degree of safety considerations that they are today.

00:02:33 Today, even such simple demonstrations would be carried out with the proper regard for safety glasses, shields, protective gloves, laboratory coats, and visible fire extinguishers.

00:02:48 The principle of safety first would be explicitly present as part and parcel of a modern Tempest in a Test Tube.

00:03:18 .

00:03:43 Tempest in a Test Tube, a series of experiments designed to explain the mysteries of chemistry and the laws that govern it.

00:03:58 Produced by KQED San Francisco, in cooperation with the California section of the American Chemical Society, for the Educational Television and Radio Center.

00:04:23 And now let's go to our laboratory and meet Dr. Harry Sello.

00:04:31 Hello, just catching up on my news. Well, I might as well show you a little experiment on what the news in a newspaper can be used for.

00:04:42 Here's a handy piece of laboratory equipment, a little board and newspaper, nothing inside. Let me spread the newspaper down on the board.

00:04:55 Equipment out of the way here. And just to show you how potent this news is, I hit the board a sharp lick, and lo and behold, a few pieces broke off.

00:05:20 Let's try that again. That was rather nice, wasn't it? At least I think so. Same thing. Heavy news these days.

00:05:37 The experiment just illustrated that we live in a very interesting atmosphere around us. And this is the title of this talk.

00:05:51 Some interesting observations about the atmosphere around us. The newspaper is about, oh, 30 inches by 20 inches in size. That's 600 square inches.

00:06:03 We know that there is an atmosphere of air all around us. We breathe it. This atmosphere exerts a pressure upon us.

00:06:11 The pressure is about 15 pounds per square inch. So that with the newspaper spread out flat on the table, no air underneath it, it took about 15 pounds for every square inch to lift up the paper.

00:06:26 So 600 square inches times 15 pounds is 9,000 pounds of force being exerted down on the paper. Well, that's four and a half tons. No wonder hitting the board caused it to break rather than to lift the newspaper off the table.

00:06:43 Well, this is a good parlor trick. You might try this sometime. The idea is, however, to lay the newspaper flat so that no air can sweep in around it, so that the board acts against the atmosphere or the atmospheric pressure around us.

00:06:59 Let's look at some other observations concerning the atmosphere around us. Atmosphere. Here's another little parlor trick. Ordinary little jar.

00:07:23 Loose cap. Pour some water in this jar and take a little white card. Place it over the top of the jar, making sure that the card covers the lip all the way around.

00:07:41 Invert the jar. Best to have a little tray handy so that in case something goes wrong, you won't wreck your best dinner tablecloth. Make sure that the card is good and wet and it's sealed all the way around here.

00:07:56 Shall I take my hand away? Whoops. Whoops. All right, I will.

00:08:03 What holds the water in the jar?

00:08:05 The water is held in the jar by atmospheric pressure. This same air pressure that caused the breaking of the board when I hit it exerts its effect on the water so that gravity pulling on the water cannot push the card aside and water escape.

00:08:33 Let's examine a little bit more in detail what we mean about this atmospheric pressure. Here we are living at the bottom of a tremendous sea or a tremendous ocean of air, just like fish, for example, live at the bottom of a tremendous ocean of water.

00:08:46 The fish don't quite know that they live on the bottom of the ocean, they just live in it. The reason they don't know and the reason you and I don't pay too much attention to the atmosphere around us is that we have just as much of the atmospheric pressure inside of us as we have on the outside of us so that we can walk back and forth and run and jump and barely ever notice that there is an atmosphere around us or pressure upon us.

00:09:07 However, sometimes you go into an elevator and if the elevator goes up particularly quickly, you'll notice your eardrums will pop. This is a piece of evidence to show that there is pressure being exerted upon all of us from day to day.

00:09:21 You see, you step into the elevator at ground level, you have a certain pressure inside of you. As you go up, the pressure around the outside of you decreases. That means that the pressure inside exerts a force outwards.

00:09:33 You usually feel this upon your eardrums because they're the most sensitive part of you as far as pressure is concerned. So that your eardrums pop and you swallow or chew a piece of gum, you take in some of the air that's around you at this lower pressure and you equalize your pressures.

00:09:50 Here's another interesting little demonstration that will show just what the atmospheric pressure can do. Here's a jar in which I just poured some water. The jar is covered with cheesecloth. I'll just put a little bit more water in it.

00:10:05 I think if I use the beaker it'll be a little handier. Cheesecloth on top of the jar. I'll just carefully pour a little bit of water into the jar through the cheesecloth. This is pretty coarse cheesecloth so the water can go right through.

00:10:22 There. Now that's about enough. Now again, if you wish to do this in your parlor, be sure you have a little pan handy. Turn it over and there you are.

00:10:45 One-way cheesecloth. The water can go through it when poured but can't come back out again. That was a little bit of a splash. Some water did escape. Well, the same principle again. The atmosphere around us is exerting pressure in all directions. Some of that pressure is being exerted right on the top of the cheesecloth.

00:11:04 The air wants to get in but the water also wants to get out. The water can't get out unless the air gets in and vice versa so that the water stays put. No movement. Well, you might ask, how come the water got in in the first place? Here's the answer. Supposing I just tip this gently, not as quickly as I did before, and hold it in that position.

00:11:31 Notice that the water runs out rather freely. But as soon as I turn it over quickly, it stops. The reason is that air can now get in. The pressure on the inside and the outside can equalize so that the water can't escape. That's exactly what happened when I filled the water through the cheesecloth to begin with.

00:11:49 As I poured the water in, I poured it in slowly. The air could get out around where I was pouring the water in. But when I inverted it rather quickly, I didn't give the air a chance to get back into it so the water had to stay put.

00:12:04 Now these are little simple experiments which show that there is an atmosphere around us and that it exerts a pressure. This matter of an elevator is yet another example. But the scientist prefers to be just a little bit more elegant about this and he uses instruments to measure this atmospheric pressure. Just how much is it? Well, I've said it was 15 pounds per square inch but supposing you didn't know, how could you measure it?

00:12:31 Well, here is a tube, a glass tube, which just before the start of the talk I filled completely with mercury up to the top. Mercury from this little jar. This is an element, a metal, which in its ordinary state is a liquid and has interesting properties because of the fact that it is a liquid.

00:12:52 I will pour a little bit of this mercury right down in the dish. Mercury flows rather easily. In fact, it flows through smaller holes than water can flow through. If you've ever played with it, you'd notice that.

00:13:06 Now I'd like to make one special point at this time about mercury. Mercury should be handled very gingerly. It is poisonous and at all costs must not be allowed to get into the system in any way. You must not breathe mercury vapor nor handle mercury too much with your hands.

00:13:30 This old trick I remember that we used to do back in high school, for example, to coat a copper penny with mercury and then go around to try to pass it as a dime. Of course, this doesn't work. You can't fool anybody with it. But it's also very dangerous because mercury, as I say, is a poison, can get through the very skin of your fingers upon prolonged exposure and so should be handled with only a minimum of contact.

00:13:54 In fact, this experiment was chosen because it's a very short one, at least I hope it will be, so that the lecturer would not be exposed to mercury for any great length of time.

00:14:05 Let me now unhook this, unclamp rather, this long tube full of mercury. It's completely full. I took great care, at least I think I did, to fill it so there would be no air in the tube from the bottom of it here to the top of it, which when I just turn it over will be inverted.

00:14:25 Now, you need about three hands to do this one. Let me just clamp my finger over the end, turn the tube over. This is the sealed off end up here now at the top. At the bottom I'm holding the mercury in with my finger.

00:14:47 And let's see if I can get the...

00:14:57 There. Notice that I made a big fuss about not touching mercury. Well, I just did. I tried not to touch it for very long and immediately after this talk I'll be very careful to wash up.

00:15:08 The level of the mercury now has dropped to where it is all the way down to here, right where my finger is, so that the column of mercury now reaches from the dish up to this level.

00:15:23 I'll just clamp it in so it doesn't topple over.

00:15:27 Notice that turning it over the mercury did not empty itself, as you might expect, and go all the way back into the dish and drain the tube.

00:15:36 Why didn't the mercury come all the way out of the tube? The reason is the atmosphere around us exerts a pressure, as we've mentioned several times now, upon the level of the mercury in the dish.

00:15:48 This keeps a column of mercury up in the tube, which is equal in the pressure that it exerts on the mercury surface to the air pressure around us.

00:15:59 Well, the chemist quite often doesn't measure a pressure. He talks about a height of mercury.

00:16:06 Here's a stick which measures height, and right now I see that this is just about 29 1⁄2 inches high.

00:16:13 The level of the mercury in here is just about 29 1⁄2 inches high.

00:16:17 So when you talk about pressure, you talk about 29 1⁄2 inches of mercury.

00:16:21 When somebody says, what's the pressure today? You say, well, it's 29 1⁄2.

00:16:25 That means the pressure is equal to 29 1⁄2 inches of mercury.

00:16:28 This is the pressure which the atmosphere exerts around us usually.

00:16:34 The instrument which measures this pressure is called a barometer.

00:16:38 And we will have more to say about a barometer in the next experiment.

00:16:46 But before we do the next experiment, let's start the one right after that.

00:16:57 I'll just put the burner under this pot of water which has been simmering here for a while and make sure it gets heated even more.

00:17:09 So that it will be good and hot when we come around to it.

00:17:16 Well, this first column of mercury that I showed you was a rather crude barometer.

00:17:22 The word barometer is taken from two parts, baros, meaning weight, and meter, meaning to measure.

00:17:32 Barometer, then, to measure weight.

00:17:34 Strictly speaking, it's not exactly weight that it measures, it really measures pressure.

00:17:41 Or the pressure exerted by a column of mercury or any other liquid which can be used for this purpose, mercury being the most common.

00:17:50 Here is an arrangement of a column of mercury which is a little bit more elegant yet than this rather crude one which I just demonstrated.

00:17:59 In this one, the tube has already been inverted and the mercury dropped down to its proper height due to air pressure.

00:18:10 There is a little reservoir of mercury in the jar on the bottom.

00:18:15 Extending out of that is a long glass tube which contains the column of mercury.

00:18:19 Now, the level is right about here.

00:18:23 As it sits right there now, it is recording, it is measuring atmospheric pressure.

00:18:28 Let's just check our previous reading to see how close the accurate barometer came to the crude one.

00:18:37 Use our meter stick again.

00:18:40 This time, let's use, instead of inches, we'll use centimeters, which is a favorite unit for the chemist.

00:18:48 Now, my eye, the way I'm standing here is not too accurate, but I think we can get a fairly close reading.

00:18:54 This says just about 77 centimeters from the top of the mercury level here to the top of the column.

00:19:05 Check back on this one.

00:19:08 Quickly, we find that this is, well, this is a little low. This says just about 74 centimeters.

00:19:15 The reason for the difference is that in turning the column over,

00:19:20 I did not have a good seal with my finger at the bottom under the level of the mercury in the dish,

00:19:26 so a little air sneaked up into the column and it's recording too low a pressure.

00:19:30 The principle is there, but the reading is not quite accurate.

00:19:33 This, however, is an accurate reading.

00:19:37 How does a barometer measure pressure?

00:19:39 Onto this little jar, I have attached a squeeze bulb by which I can change the pressure on the surface of the mercury.

00:19:47 By squeezing it, I can increase the pressure a little bit. Let's see what happens.

00:19:52 I'll now just squeeze it, and there, I can bounce the mercury up.

00:19:57 Let it drop back down again. You see, it's a very sensitive thing.

00:20:01 I'm not doing anything to it except just waiting for it to settle down.

00:20:04 Give it another squeeze now as if the pressure were increasing.

00:20:07 And it rises up.

00:20:09 That's exactly what happens when the pressure in the atmosphere around us increases.

00:20:14 By reversing the bulb, I can apply a little suction.

00:20:19 In the same manner, I'll squeeze the bulb now, and the mercury goes down.

00:20:27 Let's let it settle down a little bit, and give it another squeeze.

00:20:36 Give it another squeeze, mercury goes down.

00:20:39 How does pressure change in the atmosphere around us?

00:20:44 Well, usually pressure changes because there is more or less moisture in the air.

00:20:50 When the air is moist and warm, the pressure will be low,

00:20:53 because water vapor substituted for air tends to make a given volume of air a little lighter.

00:20:59 When the air is cool and dry, it is more dense, and hence exerts a higher pressure.

00:21:05 So by using a barometer, by taking barometer readings over various parts of the country

00:21:11 and charting the pressures, we have a way of telling whether the air is warm, dry,

00:21:17 warm, or moist, or dry, or even cool, and so forth.

00:21:24 Actually, we combine the readings of a barometer with the readings of a wet and dry bulb thermometer,

00:21:29 and between the two of them we can talk about humidity and atmospheric pressure.

00:21:33 Here is an instrument, which is a little more commonly used even than the mercury barometer,

00:21:39 in that it's more often seen.

00:21:41 It's a different kind of barometer, it doesn't use mercury, it just uses a little accordion space.

00:21:48 It has in it little bellows, metal bellows, which expands and contracts with changes in the air pressure.

00:21:54 A needle then turns and records a reading directly.

00:21:57 It is now open to the atmosphere, and you'll note that the reading says

00:22:02 just about 77 centimeters, which is the same as the reading we got with the meter stick.

00:22:08 I can attach this bulb, just as I did before,

00:22:11 and by squeezing it, increase the pressure, and we can increase the pressure on the dial.

00:22:19 By the way, this already has on it a scale behind it,

00:22:23 which tells just what the weather would be.

00:22:27 The 77 centimeters of pressure corresponds to very dry.

00:22:31 Well, if you think it's very dry, let's just change the weather a little bit.

00:22:36 Squeeze the bulb, and we make it a little bit different, even more dry than it was.

00:22:46 If I applied a little suction, I could make it go the other way.

00:22:48 Now the weather, of course, is important to many people.

00:22:51 The weather meaning the changes in pressure and the humidity.

00:22:54 It's important to pilots who want to know the pressure at all times,

00:22:58 or the weather at all times.

00:23:00 It's important to farmers who wish to regulate their harvesting as much as they can by the weather.

00:23:04 So the weather department has put out, puts out regularly a map,

00:23:09 which can be obtained from the government,

00:23:11 which looks something like the one I have here.

00:23:14 Here is a typical weather map.

00:23:16 It's a map of the United States,

00:23:21 plus something up here in Canada near Alaska,

00:23:25 and a lot of funny looking lines on it.

00:23:28 These lines, which go around in closed areas,

00:23:36 are what we call, or what the weatherman calls, isobars.

00:23:41 Iso means constant.

00:23:44 Bar is the same as the root for barometer,

00:23:48 means weight or, in our discussion, pressure.

00:23:51 So isobar means constant pressure.

00:23:54 So along these lines, in the country, along all these lines,

00:23:58 the pressure is constant.

00:24:00 It is the same at all points along the curve.

00:24:02 It's the same along all points of this curve and so forth.

00:24:05 Now you also see some spots marked H and L.

00:24:10 This stands for high and low.

00:24:13 Nothing complicated about that.

00:24:15 These are areas of high pressure,

00:24:17 while these are areas of low pressure.

00:24:19 So visualize the area of high pressure as a sort of a hill of pressure.

00:24:23 It's highest right at the center,

00:24:25 and the lowest at the bottom.

00:24:27 So visualize the area of high pressure as a sort of a hill of pressure.

00:24:31 It's highest right at the center, at the peak,

00:24:33 and slopes off as you go away from the H,

00:24:35 and comes up again as you come toward the next H.

00:24:38 Well, without going into too much detail,

00:24:40 by charting these every hour or so,

00:24:43 the weather bureau is able to plot the movements,

00:24:46 or chart the movements of these H's and L's,

00:24:48 and predict how a storm will move.

00:24:50 In general, air will move from high area pressures to low area pressures.

00:24:54 In this way, we have a reasonable way of predicting weather.

00:24:58 Let's look at yet another effect of barometric pressure,

00:25:02 or the pressure of the atmosphere around us.

00:25:07 The water in this flask has now been simmering for some time,

00:25:10 actually boiling.

00:25:12 I'll take the burner out.

00:25:15 It's hot enough for our experiment.

00:25:18 Now, by raising the flask a little,

00:25:21 I think I can stop the boiling completely.

00:25:25 Just about stopped.

00:25:27 Let's put a cork stopper in the top of it.

00:25:30 Let's see that this is going to be a little hot to handle.

00:25:43 Nice, tight fit on the cork stopper.

00:25:52 Now, the water here was boiling.

00:25:55 That means that the temperature of the water,

00:25:57 at our atmospheric conditions, as they are right now,

00:26:00 is about 100 degrees centigrade,

00:26:03 which is the boiling point of water.

00:26:06 Stopped boiling, so the temperature must be 100 degrees or somewhat less.

00:26:14 I'll just put the flask in the dish,

00:26:16 this time slip off the glove,

00:26:17 and just hold the flask here on its side.

00:26:26 Let's squeeze some water,

00:26:28 cool water that I have here in this other dish,

00:26:30 over the flask.

00:26:34 There.

00:26:40 Cool it off just a little bit more.

00:26:47 Notice that while the water had stopped boiling before,

00:26:52 it has now started to boil.

00:26:54 Isn't this a strange one indeed?

00:26:56 I can actually boil the water in this flask

00:27:01 by cooling it.

00:27:08 There it is boiling again.

00:27:10 Bubbles are coming to the surface,

00:27:12 both from the arm here and from the inside of the flask.

00:27:15 I'll cool it some more,

00:27:18 and even a little bit more,

00:27:20 just to make sure that it gets a little cool.

00:27:24 It's boiling just about as much as it was boiling

00:27:27 before I took it off the burner.

00:27:29 How is it possible now that

00:27:32 I can cause water to boil by cooling it?

00:27:38 Let's look at just what boiling is in order to explain this.

00:27:46 When the flask was boiling up here over the burner,

00:27:50 little bubbles of steam were forming

00:27:53 in the body of the liquid and were rising to the top.

00:27:57 In fact, if you ever watch a glass kettle on your stove boil,

00:28:02 you will notice that from the point that it starts to boil,

00:28:05 little bubbles will first form around the sides of the glass

00:28:08 and then the bottom.

00:28:10 These bubbles may either rise to the top

00:28:12 or may just disappear.

00:28:13 When they disappear, they make a little noise,

00:28:16 sort of a crackling noise or a humming noise.

00:28:18 This is what's known as a kettle singing just before it boils.

00:28:22 The noise is caused by some of the little steam bubbles

00:28:24 being squeezed out of existence

00:28:26 by the pressure of the water above them.

00:28:28 When more heat is applied,

00:28:30 the pressure in the bubbles of steam gets higher and higher

00:28:34 until it is equal to the pressure in the atmosphere

00:28:39 around the boiling water,

00:28:40 so that the steam bubble now rises to the top.

00:28:43 So we have here a definition of boiling.

00:28:46 A liquid will boil when the pressure in the bubbles

00:28:49 is equal to the pressure on the outside of the liquid.

00:28:54 This means now that you should be able to change

00:28:57 or affect the boiling point of a liquid

00:28:59 by merely changing the pressure on the liquid above it.

00:29:02 This is precisely what we did here.

00:29:04 When this was open to the atmosphere,

00:29:06 the pressure was, as we previously measured,

00:29:07 about 77 centimeters of mercury.

00:29:11 This meant that the boiling point of water

00:29:13 was very close to 100 degrees centigrade.

00:29:15 I say very close because it's actually 100 degrees centigrade

00:29:18 when the pressure is 76 centimeters.

00:29:21 When it's 77 centimeters,

00:29:23 it's just slightly, slightly above 100 degrees.

00:29:27 Now, when I cooled this,

00:29:30 I cooled the vapor in the gas cap above the liquid.

00:29:35 This reduced the pressure on the liquid.

00:29:37 The pressure in the vapor made a lower pressure

00:29:41 over the liquid than there was before.

00:29:43 This meant now that the water could boil

00:29:45 at a lower temperature because the pressure

00:29:47 above the liquid was reduced.

00:29:49 If I increase the pressure above the liquid,

00:29:51 I'll make the water boil at a higher temperature.

00:29:53 In a pressure cooker, the latter is what happens.

00:29:56 The pressure cooker is completely sealed.

00:29:58 Steam pressure builds up above the liquid,

00:30:00 increases the total pressure above the liquid,

00:30:03 so that little bubbles have to form

00:30:05 at a higher pressure than they did before

00:30:07 in the liquid, so that the boiling point

00:30:09 of the water is raised.

00:30:11 If you take this experiment up to a mountaintop

00:30:13 or, say, someplace like Denver,

00:30:15 you find that the pressure is so low up there

00:30:18 that the water boils at a much lower temperature

00:30:20 than 100 degrees centigrade.

00:30:22 This means if you want to make a three-minute egg

00:30:24 at Denver, you have to cook it a little bit longer

00:30:26 than you do at sea level.

00:30:28 So the pressure can affect the boiling point.

00:30:33 Let's summarize, then, as to what we've seen here

00:30:37 so far.

00:30:39 We said that we live in a very interesting atmosphere

00:30:43 around us.

00:30:45 This great ocean of air that we breathe and live in

00:30:48 exerts a pressure upon us.

00:30:50 The evidence for that pressure was shown

00:30:52 by a little experiment of one-way cheesecloth

00:30:55 in which you could invert a flask of water

00:30:57 and it would be held up and not run through

00:30:59 the cheesecloth.

00:31:01 The same with a card on the flask

00:31:03 so that you could invert that and the water

00:31:05 would not run out due to the air pressure.

00:31:07 The instrument for measuring pressure

00:31:09 is known as a barometer.

00:31:11 Barometer measures weight or, more strictly speaking,

00:31:13 pressure.

00:31:15 Column of mercury.

00:31:17 In this case, equal to 77 centimeters.

00:31:19 This is equivalent to 15 pounds per square inch.

00:31:22 It is important to record pressures from day to day

00:31:26 because we use weather maps.

00:31:28 These weather maps, which look like this one here,

00:31:31 have lines on them of constant pressure

00:31:33 called isobars.

00:31:35 A line is an isobar.

00:31:37 It indicates pressure.

00:31:39 High pressure areas and low pressure areas exist.

00:31:43 Winds then form.

00:31:45 Finally, we showed we could change the pressure

00:31:47 and change the boiling point of a liquid.

00:31:49 Thank you.