00:00:00 Hello, I am Harry Sello. It is my pleasure to introduce Tempest in a Test Tube, a television

00:00:10 show which made its debut August 24, 1955 on KQED Channel 9, the educational station

00:00:19 for the San Francisco Bay Area. Tempest was a series of 53 half-hour shows pioneering

00:00:27 a new approach in which I, as lecture demonstrator, gave live, unrehearsed presentations of a

00:00:34 series of chemical experiments. These were designed to illustrate basic, simple chemical

00:00:40 principles. The purpose was to stimulate an interest in chemistry by teenage students

00:00:47 and by adults. The talks and experiments had to be entertaining, educational, and simple.

00:00:56 Curiosity and liveliness were key to the approach. All the experiments used in the shows were

00:01:02 designed and constructed by members of the California section of the American Chemical

00:01:07 Society. The participants were employed by the Shell Development Company, Emeryville,

00:01:13 and by Chevron Research, Richmond. A grant of $52,000 from the Ford Foundation and National

00:01:21 Educational Television permitted the filming of the first 24 shows of the series. The management

00:01:28 for the ACS consisted of Alan Nixon, section chair, Fred Stross, TV committee chair, myself

00:01:36 as first emcee, and Aubrey McClellan, second emcee. We four constitute the core of the

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

00:01:54 The senior chemist committee of the California section today is determined to revive Tempest

00:02:01 for the benefit of elementary schools, high schools, adult education classes, ACS local

00:02:08 collections, historical archives, TV stations, and similar organizations. We believe in chemistry

00:02:16 as a second language. While basic principles have not changed, practices have. Forty-five

00:02:25 years ago, such simple chemical demonstrations were not treated with the degree of safety

00:02:31 considerations that they are today. Today, even such simple demonstrations would be carried

00:02:38 out with the proper regard for safety glasses, shields, protective gloves, laboratory coats,

00:02:46 and visible fire extinguishers. The principle of safety first would be explicitly present

00:02:53 as part and parcel of a modern Tempest in a Test Tube.

00:03:23 Tempest in a Test Tube, a series of experiments designed to explain the mysteries of chemistry

00:03:52 and the laws that govern it. Produced by KQED San Francisco, in cooperation with the

00:04:06 California section of the American Chemical Society, for the Educational Television and

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

00:04:24 Hello. The title of this talk is, What is a Flame? Have you ever seen the shadow of

00:04:33 a candle flame? You are now looking at just that. Isn't it a surprising thing that a small,

00:04:44 seemingly very light substance like the flame of a candle can throw a shadow? It does, as

00:04:53 you can plainly see. Note that there are in this shadow several zones. An inner zone,

00:05:03 which is a little bit darker than the outer zone. We all know that a material to cast

00:05:13 a shadow must be something solid, or more scientifically speaking, must be opaque to

00:05:19 light. That is, light cannot be able to go through it or must not be able to go through it. But

00:05:26 there must be then something in this candle flame which is opaque to light or blocks the

00:05:31 passage of light because the candle flame throws a shadow. This is the significant point,

00:05:37 the shadow of the candle flame. You and I can throw a shadow very easily, some of us perhaps

00:05:41 a slightly bigger shadow than others, maybe a little bit too much of one sometimes. But the

00:05:48 shadow of a candle flame is caused by the fact that there is solid material in the flame of

00:05:53 the candle. This can be illustrated by the following experiment. In our last talk we

00:06:04 pointed out the various parts of a candle, the solid fuel or wax, the wick, and the flame. The

00:06:12 wax melts, rises up through the wick by capillary action. The melted wax vaporizes, changes into a

00:06:20 vapor, and the vapor burns. This is the process of how a candle burns. Now exactly what is the

00:06:27 nature of this flame? That is, what is it made of? We've shown the zones, it casts a shadow. Well,

00:06:33 let me hold this little white dish this way. There. Note that the white dish is now well

00:06:46 covered with a layer of soot. This soot can be wiped off, there's my finger, not too dirty I

00:06:53 hope. No soot on it anyway. Very loose on the white surface of the dish. The soot in the candle

00:07:04 flame, the solid material, although it's tiny particles, is what caused the shadow of the

00:07:09 candle flame. That's something to remember. There is solid material, solid particles, soot, in the

00:07:16 flame of a candle. The chemist would more properly call this not just soot, but carbon. The carbon

00:07:23 comes from the fact that the original wax, the fuel, which is vaporized to burn, contains carbon

00:07:29 to begin with. But that process, namely how carbon got into the candle and so forth, will be discussed

00:07:35 at another time. The point is here that the flame contains a solid matter. I've said that there are

00:07:43 various zones in the candle. Let's look at a more detailed drawing of these various zones.

00:07:48 Here's the solid portion, the wax, the wick, melted wax, some dripping over here, actually

00:08:01 solidified, these papers hard, solidified the wax. We have an inner zone, which is dark,

00:08:09 labeled here a gray zone. Well, to some it's gray, to some it's invisible, but nevertheless much

00:08:16 darker than this next outer zone, which is bright, so-called yellow or luminous zone. Luminous means

00:08:25 giving off light. In this little candle standing next to the cardboard, that is the part that's

00:08:31 quite visible, the luminous portion of the flame. Then a part, a third part, which is very difficult

00:08:40 to see with the eye, but does exist, is a blue or hot zone. Now when I say hot, and something is

00:08:50 being cold in a candle flame, or hot, I mean just relatively or comparatively speaking. That is,

00:08:55 the outer side is the hottest portion, the next inner region is less hot, and the final region,

00:09:03 the innermost, is just colder than the rest. But this is commonly called a cold zone. It isn't the

00:09:08 kind you want to put your finger in, it's not that cold, but it's just cooler or colder than the outer

00:09:13 region. Let's now see if we can discover whether this is really true, whether the candle has various

00:09:22 zones. Here I have a little wooden stick that I've been using as a pointer. Let me just touch this

00:09:30 across the, so, well, there, right on the wooden stick is a smudge mark, which has darker smudges

00:09:41 on the outside, and a very light smudge on the inside. Meaning, that as you lay the stick across

00:09:48 the flame, this part deposits the carbon, causing the smudging. But the inner portion doesn't deposit

00:09:56 any carbon, it's not as hot as this one. So there is a difference in the various parts of the flame.

00:10:02 If it were all the same kind, all the way across, we should get a pretty even smudge mark. Now,

00:10:07 actually, this is not too good a difference to show here. Let me try this once more. Well,

00:10:15 that one, the candle was burning, I'll take a fresh stick. The candle was sort of waving in

00:10:19 the breeze there, burning every which way, I should say. I'll try this again, just barely

00:10:23 touch it in. There. Right where I'm pointing, there are two smudge marks in between a vacant

00:10:31 space, as if nothing had happened in between the two smudge marks, but only at the smudge

00:10:36 marks. Well, let's not make too much of a case of this. Try it with a card, and maybe see if

00:10:41 we can illustrate it that way. This depends very much on whether the candle flame decides to stand

00:10:45 still. There. What you see here are rings. One, another one, another one on the outside of that.

00:11:00 These successive rings are caused by the movement of the card, but consider just one ring alone.

00:11:05 This shows that the outer region of a candle has scorched the card, whereas the inner region hasn't.

00:11:10 The difference in the zones. The luminosity in a candle flame is caused by the glowing

00:11:20 particles of soot. These little particles glow to a white heat and escape from the flame,

00:11:27 and in glowing, they give off this light. But a candle is not the only material which can give

00:11:34 a flame when lit. Here is another object which can do the same thing. A Bunsen burner. This

00:11:42 burner was invented by a man named Bunsen, hence the name. Let me light it and show you the various

00:11:50 parts of a Bunsen flame, or a Bunsen burner flame. I'll show you the various parts of a flame and

00:12:03 perhaps scorch the lecturer too. Note that we have the bright luminous flame in the burner.

00:12:13 This can be adjusted by cutting down the amount of gas. There is a thumbscrew on the bottom of

00:12:18 the burner which can adjust the flow of gas, cut it down or increase it, and cause a yellow flame

00:12:25 very similar to that of the candle. It is possible to change the luminosity of a burner flame where

00:12:34 it isn't possible to change the luminosity of a candle flame. The difference is one of how you

00:12:39 get the air into it. If I open this burner by twisting it, I allow more air to come into the

00:12:46 holes in the sides to mix with the gas. This causes the luminosity to decrease. Twist it even

00:12:56 more and pretty soon you can make the yellow almost disappear. Now the luminous part of the

00:13:08 flame is gone and all that's left is a very faint bluish cone. There is a flame there however,

00:13:16 definitely. By increasing the amount of air I have caused the luminous portion of the flame

00:13:26 to disappear. This is what the candle could not do. The burner has air coming up the center along

00:13:33 with the gas. It gets all the air it needs for its flame. The candle does not have any air coming up

00:13:38 its center. It's solid, so it can only get its air from the outside. So the inner portion of a candle

00:13:45 flame must remain just a poorly burning unit, rather luminous, which is a clue, this luminosity

00:13:53 which is a clue to the efficiency of a flame. If a flame is luminous, which you get by cutting down

00:14:01 the air, it's not very efficient. It has a lot of carbon. Carbon it burns, so it should be used up.

00:14:06 If a flame is efficient, then it should be blue. No visible yellow. There is always a slight roaring

00:14:20 when the flame burns properly. The roaring is due to the air rushing up to be burnt. Now the

00:14:26 hottest portion of a Bunsen flame is right above the tip of the cone. I can illustrate this by

00:14:30 holding this wire in the flame. The wire is now glowing. If I lower the wire so that it touches

00:14:44 the blue cone, you'll see what happens. It is now glowing at the outer portions of the flame,

00:14:54 but not at the inner portion. This means that the central part of the flame is colder than the outer

00:15:00 portion, the same as in a candle flame. We can further illustrate this a little more dramatically

00:15:07 by taking a wooden match and putting it right into the cold portion of the flame. It doesn't

00:15:19 light except that time. It doesn't take long for it to get warmed, so it will light, but let's try

00:15:26 that again. Let's raise this a little so I can see the blue cone a little bit better. By the way,

00:15:45 I am running into some of the same trouble that most photography runs into when it tries to

00:15:50 photograph a blue flame. It's very difficult to see under bright lights. That's why in a movie

00:15:57 of a chemistry lab, you generally always see a yellow flame, not a blue one. It's just that

00:16:01 the blue one can't be photographed. There. If I put it in at the bottom where it's cold,

00:16:07 just once more to make sure, the match head will take some time to light. There. The fact

00:16:18 that there is cold gas in the center of this can be illustrated by a little bit of an experiment

00:16:24 here. Let me make this a little more luminous so now it can be seen without roasting a lecturer.

00:16:33 I'll put this hollow tube right at the tip of the burner. This time I want to light the match,

00:16:40 and light the gas that's coming out of the tip of the tube. We now have two heads to this flame,

00:16:50 one at the burner, one at the tip of the glass. There must be cold unburned gas going up through

00:16:58 this tube, otherwise it wouldn't be a flame at the top. If I lower this slowly, the little flame

00:17:04 disappears, or certainly shortens, because I'm slowly shutting off its supply of gas. The gas

00:17:11 is escaping without going up the tube. If I raise it, it comes back. Lower it, it slowly disappears.

00:17:18 Raise it again, and it comes back. Now, this then shows the essential differences between a candle

00:17:30 flame and a burner flame. Air and gas come up, are burned at the top, hot air rises. It rises

00:17:37 until it gets very hot. It rises until it gets so hot that the lecturer is forced to mop himself

00:17:42 every once in a while so that he can proceed more comfortably. Now, the hot air is certainly coming

00:17:53 from this particular burner. In the previous show, we discussed a little bit about this hot air,

00:17:58 but let's look further at this property of the hot air rising. Here I have a plate,

00:18:03 hot plate, which has been hot for some time now. I'll put this steel beaker of water on it.

00:18:08 Just beginning to get hot, really simmering. I have a glass flask with a long neck,

00:18:19 commonly known as a volumetric flask for those of you, those of you that have worked with this

00:18:24 sort of material. The top of this flask has a balloon attached to it. Now, when we started,

00:18:30 the balloon had no air in it because it was cool, but since it's been sitting around under the

00:18:36 lights here and next to the hot plate, the air has warmed up a little bit, but I think there

00:18:41 will be enough change to show the experiment. Let me immerse this flask in the hot water,

00:18:46 and clamp it down so it will hold. A few more turns. Now, lower it into the,

00:19:06 there. The empty flask that is the air full of, flask full of air rather, excuse me,

00:19:16 is now in the hot water, and the balloon is expanding, whoops, and now it is certainly

00:19:24 getting more and more air into it. The water is not yet boiling. When it gets to boiling,

00:19:31 this will expand perhaps even a little bit more. This demonstration shows that when cold air is

00:19:41 heated, it expands, and it occupies a larger volume than it did before. We had only a flask

00:19:49 full of air before, with very little in the balloon. Now that same amount of air, none has

00:19:55 been added, none has been taken away, has spread itself out, expanded, if you will, until it has

00:20:00 gone into the ball. Let's look a little further into the question of what it means when hot air

00:20:07 expands. I'll just turn this off, take this away here, and, there, and in this

00:20:37 experiment, we'll show, well, why tell you? Let's watch. Here I have a peculiar kind of a balance,

00:20:48 composed of a bar on which is resting a piece of a meter stick, carefully balanced. There's a little

00:20:58 copper rider here, which I can slide back and forth to put it in balance. Actually, it's darn

00:21:03 close to balance right now. These are two cans, empty paint cans, which are, from which the bottoms

00:21:13 have been cut. There's space up in here. They're empty. Light the candle. Let the flame develop a little bit so it gets a good source of hot air.

00:21:43 Now, I will just place the candle in this position, right under one of the pans, one of these empty cans, or if it were a balance,

00:21:54 you'd call it pans. It'll take a little bit here for the candle to get a nice high flame. This is very delicately balanced on a pivot in the center.

00:22:14 Now, I'll just lift this a little bit. And, you can see what is happening. The side that the can is on, the side that the candle is on, or the can that the candle is under, I should say, has risen.

00:22:38 What does this mean? This means, quite obviously, that this side of the balance, the side with the candle, is lighter than this side, or stated in reverse, this side is heavier than this side.

00:22:57 What I have done is to allow hot air to rise into this can. Both cans are the same volume, that is, they have the same space. So, there is the same volume of air in both, but this side is lighter.

00:23:15 Therefore, it means, though it has the same volume, this can, it contains less weight. Now, when the chemist talks about the weight for each unit of volume that a substance has, he's really talking about the density, or stated in somewhat simpler terms, density is weight divided by volume, density.

00:23:45 Now, as this side is cooling off, why the air is becoming more dense, increasing in density, and it's coming down again. Let's see if we can make it go up by heating it once more. There.

00:24:05 This now shows that hot air is less dense than cold air. This is a significant point in this experiment. And it is less dense because it expanded. In a later talk, we will have something to say about the actual molecular construction of this air, of just what happened in terms of molecules, but for this time, let it suffice to say that when hot air is, when hot air expands, it decreases in density.

00:24:35 Therefore, it can rise. This principle of hot air rising was actually made use of commercially many years ago by the use of the hot air balloons. A fellow would come along and dig a big hole in the ground and have a tremendous cloth balloon, which he would hold over a fire that he built in this hole in the ground, and trap the hot air in the balloon.

00:24:58 The balloon would then rise, and if it had a basket underneath, it could carry him up in the air. Of course, you might ask, what happened when the hot air cooled off again? Well, the balloon would come down. But the balloonist was expert enough to maneuver his balloon so he could spill out some of the hot air and come down just as fast as he pleased, not as fast as the balloon pleased.

00:25:20 But the rising of hot air is what is responsible, in great measure, to our winds and air currents. Let's look further into this matter of air currents.

00:25:29 In the next experiment, we can illustrate a little bit about the movement of air. Here I have a glass U-tube.

00:25:39 In one leg of this U-tube, there is a candle on a little stand. If I lift it out, you see there's a joint and the candle is supported on the inside there. Put it back in. It becomes one unit. Now, I'll light the candle.

00:26:09 There. Let the candle develop a bit of a flame.

00:26:26 While the candle is burning, I'd like to mention that it is this matter of hot air rising that plays an important part in the smog problem that you may have heard about in cities like Los Angeles and San Francisco.

00:26:39 You see, there you have a city, in each case, which is in a valley or surrounded by a ring of hills. This causes the air to pocket easily, to sit in this bowl.

00:26:51 Cool air rushes in from the ocean, displaces the, becomes warm, and rises, pushing its way upwards. When it reaches the top of the hill, or near the tops of the hills, the cold air on top forces it to stay there.

00:27:07 So you get a layering effect. You get the hot air layering underneath the cold air. Therefore, you have the funny sensation that if you climb a hill in L.A. or San Francisco at times like this, the temperature will actually go up as you come near the top of the hill.

00:27:24 This is called inversion temperature. When this happens, then you see fumes from automobile exhausts or incinerators or industries, whoever is responsible for smog. Fumes can then sit in the city and cause discomfort.

00:27:41 What is needed is a way to disturb this air, to move it, that is create winds. There's normally a lot of hot air in both of these places anyway, but in inversion temperature days, it can be difficult.

00:27:55 Now let's look at our little lamp, little candle burning in the chimney here. I'll hold my hand over the end here, see what happens. There, the candle went out.

00:28:08 Now what this means is that the candle is getting its air not from this side, but from this side. This is proven by the fact that when I cut off the air here, the candle goes out there. If it were getting air from this side, why then, this would not affect it.

00:28:28 Let us show this in still another way. Light it once more.

00:28:33 So, now I have here a bit of a chemical which can, when burnt, produce some smoke. Let me light my burner so I can set the chemical on fire.

00:28:57 There's an awful lot of lighting at this point, with not much light being shed on the topic.

00:29:03 The same old problem again of trying very hard to see the flame, not too visible. There, I think that's about got it. I'll put a little bit of this chemical on my spatula and set it on fire.

00:29:27 This chemical is red phosphorus. It throws up a heavy smoke. Now you can see while some of the smoke is going up, quite a bit of it is going downwards and traveling all the way through the tube and up around the candle and coming out this side, proving that the candle is getting its air supply from the side where the smoke is being generated, and there is quite a bit of smoke being generated.

00:29:54 In a later talk we will describe this in a little bit more detail. This is phosphorus pentoxide, the white smoke that you see.

00:30:01 Well, we have now demonstrated that hot air, or air, can travel. Excuse me a moment. What I mean is, what we've demonstrated is that hot air in rising here will cause other air to travel through the tube this way. A current of air will be carried through. This carrying of air currents is called convection.

00:30:22 Convection. This is commonly noticed in the operating of a hot air furnace. A hot air furnace has its gas flame at the bottom where air is warmed up. It rises up through the furnace and escapes in the top.

00:30:43 Well, let's summarize. We've demonstrated the various zones of a candle by actually seeing the shadow that a candle throws due to the soot in its flame. We've looked at a burner. It also has zones. It is a more efficient burning unit than a candle.

00:31:01 We've gone on to demonstrate that hot air expands. In the balance experiment, we caused hot air to expand in one side of a balance. In expanding, some of it actually spilled out so that what remained had less density than before, was less dense, which meant that the balance would then be lighter on that side and it went up.

00:31:24 Finally, we showed that air can travel in currents. These currents, this process being called convection. Thank you.

00:31:54 This is National Educational Television.