00:00:30 TEMPEST IN A TEST TUBE, A SERIES OF EXPERIMENTS DESIGNED TO EXPLAIN THE MYSTERIES OF CHEMISTRY

00:00:47 AND THE LAWS THAT GOVERN, PRODUCED BY KQED SAN FRANCISCO, IN COOPERATION WITH THE CALIFORNIA

00:01:02 SECTION OF THE AMERICAN CHEMICAL SOCIETY, FOR THE EDUCATIONAL TELEVISION AND RADIO CENTER.

00:01:15 AND NOW LET'S GO TO OUR LABORATORY AND MEET DR. HARRY SELLOW.

00:01:22 Hello. The talk you are about to hear is a repeat of one given about a hundred years

00:01:28 ago entitled, The Chemical History of a Candle. This talk is actually one of a series given

00:01:37 in England by a very famous scientist of that day, a man by the name of Michael Faraday.

00:01:44 Michael Faraday was called by some of his colleagues, the greatest living experimentalist

00:01:50 of that time. And we have come to recognize him as one of the greatest scientists of all

00:01:57 time. He was a very interesting person. He was a self-educated man, taught himself out

00:02:04 of books that he read, all that he knew. He didn't go to school. This doesn't mean that

00:02:11 one shouldn't go to school to get knowledge. It means that Michael Faraday worked probably

00:02:16 about ten times as hard to get what he knew than he could have, than he would have rather

00:02:21 if he had gone to school. Well, Michael Faraday started out with humble jobs in the beginning.

00:02:29 He was an errand boy, a blacksmith's apprentice. But he finally found science. When he found

00:02:35 science, he took to it as a duck to water. He got himself a job in the laboratory of

00:02:40 the then most famous chemist, Sir Humphrey Davy, who recognized in Faraday a great deal

00:02:46 of talent. Well, Michael Faraday worked and studied and rose to become head of the very

00:02:53 laboratories in which he had started as a laboratory assistant. He left behind him a

00:03:00 record of his work, among many other kinds of writings, in his diary. In this diary,

00:03:09 the first volume of which I have here, he described many of his experiments and the

00:03:15 kind of work that he did in great detail. Here is a picture of Michael Faraday in his

00:03:19 middle years. Quite an elegant gent, I would say, holding a test tube, an important thing

00:03:26 in chemistry in those days as it is today. Besides having a love for chemistry, Michael

00:03:34 Faraday wanted very much and liked very much to explain chemistry to people, in particular

00:03:43 to young people. So about this hundred years ago of which I speak, he started a series

00:03:47 of talks called Lectures to Juveniles, another word for teenagers, juveniles in those days.

00:03:56 He called these The Chemical History of a Candle, in which he explained through the

00:04:02 functioning of a candle, through how a candle worked, he explained all the principles which

00:04:07 govern our universe. And, needless to say, those principles still apply today. Well what's

00:04:14 all this fuss about a candle? Why did Michael Faraday think it was so important? Well you

00:04:19 must realize that in those days a candle was not only something which gave a flame, but

00:04:25 was used for light. So it had extra importance, more so than it has today. But if we examine

00:04:31 a candle from the light of Faraday, manner of speaking, I think we'll be able to illustrate

00:04:37 just the same principles that Faraday did. What does a candle consist of? A candle is

00:04:46 made up of three parts. A solid part, the wax or a fuel, a wick, and a flame. Why does

00:04:57 a candle do what it does? Why does it have a puddle of melted wax at the foot of the

00:05:03 wick? What is the function of the wick? Why does the flame go up? How does the wax get

00:05:10 from the bottom, where it's standing, up through the wick up to the flame? All of these questions

00:05:17 we will answer by examining each of these processes a little bit more in detail. Why

00:05:23 does the flame go up? When a candle is lit, and a flame comes, the air around the candle

00:05:33 is warmed. Well this illustrates a very simple principle to begin with. When the air around

00:05:38 the candle is warmed, by the heat that the candle generates, the air rises. As a matter

00:05:44 of fact, right at about this level, the flame of the candle is quite hot. I could prove

00:05:50 this I suppose by raising a little bit of a blister, but I think you'll take my word

00:05:55 for it. Hot air rises, more cold air comes in from the sides and sweeps up. This causes

00:06:06 a circulation of the type that I'm illustrating here with my hands. Cold air coming in, hot

00:06:12 air going up. This is what gives the candle its tapered effect in pointing toward the

00:06:18 top. This is also what is responsible for the even puddle of wax, melted wax, around

00:06:25 the foot of the wick. You see the cold air coming in keeps the outside edges of the candle

00:06:31 cool so that the wax which is melted in the center is solid at the outside, and you have

00:06:37 a little melted puddle, never running too much down the sides, but some. If the air

00:06:45 is disturbed in the room so that you can continuously blow across the candle, why

00:06:50 then pretty soon the melted wax will run down the opposite side to which you blow, indicating

00:06:55 that you disturb the flame in this direction, that is by blowing. Well, hot air rises, that's

00:07:02 the principle. Here is a simple experiment which will illustrate that perhaps a little

00:07:07 more clearly. I will light the candles that are shown here on this little toy, four of

00:07:19 them. This is a little gadget that you commonly see around Christmas time called angel shines.

00:07:37 This particular one is perhaps more correctly called racing horse chimes because instead

00:07:42 of having angels on the sides it has little horses. We said that hot air rises. The hot

00:07:47 air rising should have an effect as soon as we get a bit of a draft going here. Now, right

00:07:56 about here I can feel a little bit of the currents. Now the horses are a little reluctant

00:08:05 to start, so let's just give them a little push. There. The apparatus consists of three

00:08:21 parts, a tray containing the candles, the little horses on a frame, and a little propeller

00:08:30 at the top. Hot air rises, blows through the veins of the propeller, and so blowing causes

00:08:40 the propeller to go round and round, and the little horses chase each other around, never

00:08:44 really catching each other, a sort of a mad horse race. And now I believe it is even possible

00:08:50 to hear the tinkling of the bell being hit by the strikers dangling from the saddles

00:08:56 of the horses. We're now hitting the bell on both sides. This may seem like a rather

00:09:20 simple experiment, and why all this fuss? Now, if we use this experiment as an analogy,

00:09:27 I would like to illustrate the following. Picture, if you can, instead of the candles,

00:09:34 a very hot flame, say caused by the mixing of two chemicals, which we'll explain in later

00:09:41 talks. A hot flame, instead of the propeller, this particular little brass propeller, picture

00:09:48 a set of veins, very much more strong and much more complicated than this particular

00:09:54 propeller, a series of blades, the hot gases blasting against a series of blades, going

00:10:01 through, making these blades turn round and round and round at tremendous speeds. There

00:10:06 you have the essence of a jet plane, a gas turbine engine. Blades being operated by the

00:10:13 movement of hot air. Well, it's a kind of a simple way of looking at it here, but the

00:10:19 principle you see is the same. We'll never be able to move a plane with something like this,

00:10:24 not with just candles burning, at least not a very big plane. Probably wouldn't move much

00:10:28 more than a fly this way. But in a jet plane, this is the principle that occurs. Hot gases

00:10:35 blasting against moving blades, the blades and moving several of them, maybe a half a dozen in

00:10:43 a row, the blades in moving, causing the plane to go forward at a tremendous speed. The movement

00:10:49 of hot air through a propeller. Let's examine a little more closely just what other functions

00:10:59 a candle has in trying to answer the questions that we asked before. What is there about a

00:11:04 candle that burns exactly? I better put these out because I'd hate to think this would drown

00:11:10 out the speaker by the slight tinkling. Stopped our jet plane. What is there about a flame that

00:11:21 makes it a flame? What is it exactly that burns? To illustrate this, I would like to do the next

00:11:30 experiment here. A little wooden taper in my hand so that I can reach some distance with it.

00:11:48 Now we'll get that, let that flame get a chance to get going here. This is a candle sitting on

00:11:58 a block, surrounded, a candle surrounded by a glass tube to keep down the drafts.

00:12:09 Now if I carefully snuff this out.

00:12:19 Well, it didn't get it going hot enough. Let's try lighting it again.

00:12:28 There, it seems to be a little bit higher now. Break off this taper.

00:12:42 What you need here is a third hand in order to get into this candle. There. Now watch carefully,

00:12:49 I'll snuff the candle out again, the flame, and reach with my little taper.

00:12:55 There. You notice that the flame looks like as if it's jumping from the wood

00:13:06 down to the candle. Not only does it look like that, that actually is happening.

00:13:12 Once more. There. Now, when I snuffed out the candle, a stream of smoke or vapor rose. This

00:13:27 vapor I could light with the taper, showing that the flame actually started in the smoke and not

00:13:35 at the candle. That is, it went from the top of this glass tube, jumping down to the candle.

00:13:41 This vapor or gas or smoke, and for this talk we'll use those three words interchangeably,

00:13:47 although there is some difference between them. This vapor was flammable. That is,

00:13:52 it could burn. Flammable. Some of you might wonder, is there any difference between flammable

00:14:02 or inflammable? The answer is no. There is no difference. Both words mean the same thing.

00:14:07 However, the chemist prefers to use flammable in order to avoid the chance of making a mistake

00:14:14 in meaning. You see, words beginning with N generally mean not something or other. For

00:14:21 example, incapable, not capable. Incorrect, not correct. So that if we say inflammable,

00:14:30 you could possibly sometimes mean not flammable, but that's not so. Why have this trouble?

00:14:37 Let us avoid the use of the prefix in as far as the word flammable is concerned and just call

00:14:42 something which can burn flammable. The vapors which rise from the candle are flammable or will

00:14:49 burn. If I put this out and try this with a momentary pause in between, watch what happens.

00:14:58 Let the vapors rise a moment. Nothing happens, although there are still vapors rising. This

00:15:11 will illustrate another principle that we'll get to in just a moment. The point to remember is,

00:15:16 when the vapors have a chance to cool off, you cannot cause the vapors to burn so that the flame

00:15:24 cannot jump back to the candle. It must be that the vapors remain hot in order to burn. This will

00:15:29 be illustrated, I think, a little bit better in the next experiment. Here's a beaker placed on

00:15:38 a hot plate. Now there is some wax in that beaker now, but let me shave a few chunks of this paraffin

00:15:48 or wax, drop them in the beaker. There, I think that'll be enough. This is the same kind of wax

00:16:00 that's present in a candle. Vapors are now rising from the bottom of the beaker. There is also a

00:16:09 melt, a puddle of melted wax in the bottom of the beaker. So what do we have here? Actually,

00:16:13 we have a duplicate of the candle, only not so neatly arranged, and no wick. Now, I wish to make

00:16:23 a point of this rather obvious thing right here. The wax, by hand, is a solid. When I dropped it

00:16:29 into the beaker, it melted. The process of a solid changing to a liquid is melting, the same as ice

00:16:37 changes to water when ice melts. However, there is an additional process here, the process of

00:16:43 the liquid changing into a vapor. There. The vapor got hot enough, and finally, without any extra

00:16:55 added flame applied in the form of my matches, which I was ready to do, the vapors caught fire,

00:17:00 showing that the vapors arising from this wax, after the wax melted, were flammable as well.

00:17:07 You don't need the wick. So you might say, what's the purpose of a wick in a candle? We'll get to

00:17:12 that. This isn't a very good candle, not a very good flame, actually. It's kind of kicking around

00:17:16 all over the place, not very controlled like a candle is. But the significant or the important

00:17:22 thing is that we did form vapors by the melting and the vaporization of the wax. This process,

00:17:29 namely the process in which a liquid changes into a vapor, is called vaporization. The chemist

00:17:38 doesn't mess around. He just calls him as he sees him. Vaporization, the present, the process of

00:17:45 changing a liquid into a vapor. Note that the use of the root vapor is retained. Cut off the air,

00:17:55 and it will stop burning. Vaporization then was illustrated by the wax first melting to a liquid,

00:18:05 and then vaporizing into smoke or gas. This was allowed to catch fire by the heat of the hot

00:18:13 flame. What does the wick do in a candle? We just lit the vapors. Let's talk about the wick,

00:18:27 the wicked wick. In this experiment, I have three glass tubes dangling into a little glass tray. Let

00:18:38 me pour a little bit of this liquid into the tray. There. It's not important for me to see it,

00:18:54 just important for you to see it. Now, as soon as I poured the liquid in the tray, and it hit the

00:19:04 bottom of these glass tubes, in each tube, a tiny column of that blue liquid rose up the tube. These

00:19:13 tubes have very fine, hair-like openings in their centers. They're actually hollow tubes, but the

00:19:20 opening is very small indeed. I said hair-like. This is exactly the word I wanted to use. Because

00:19:27 this is, because these openings are so small and hair-like, they are given the name, they are called

00:19:33 capillaries. And the action by which the liquid rises up the inside of these tubes is called

00:19:40 capillary action. Capillary action. The word capillary means hair-like. The reason that the

00:19:58 column of liquid is at different heights in each of the capillaries is because the little hole,

00:20:04 or the pore, the words can be used interchangeably, the little holes in the capillaries are of a

00:20:11 different diameter. The widest one is here, the next, the more narrow one here, and the narrowest

00:20:18 is here. Therefore, the shortest column of liquid is in the widest tube, the next in the narrower

00:20:27 tube, and the tallest column of liquid is in this very narrow tube. In fact, it's all the way up to

00:20:32 here. So now we can see that the height to which a liquid will rise in a tiny little opening in a

00:20:40 capillary depends on how small the hole is. This action, capillary action. Now, with a piece of

00:20:49 Kleenex, which I had around here a moment ago, right here, let me show you a little variation

00:20:57 of this same thing. I will take the tallest column, or the smallest capillary. Let's lift this up a

00:21:05 bit, and slip this out from underneath its tape. There. Now, the others slip down too,

00:21:21 it's not important. Leave them hanging here. Now, the column of liquid in the capillary is almost

00:21:29 to the top. It's right up to here, almost full length. I will now touch this clean piece of

00:21:37 tissue to the bottom of the capillary, and there the column of liquid is immediately receding,

00:21:48 very quickly. That is dropping down. Now I'll move over to a clean spot on the tissue paper,

00:21:56 and it's dropping even further. What is happening is this. Liquid is in the capillary here, in the

00:22:06 tube, but there are capillaries in this piece of paper, this tissue paper, that are even smaller

00:22:11 than the ones in the tube. Therefore, the liquid will come out of the tube and go into the smaller

00:22:16 holes. Remember I said it likes to go higher, or more deeply, into the place where there are the

00:22:22 smallest holes or capillaries. This principle is exactly how a blotter blots, for example. You've

00:22:31 never thought about that. You squeeze a blotter onto a bit of ink, to an ink puddle, and the ink

00:22:38 spreads out right through the blotter, way beyond the distance at which you touch the little puddle.

00:22:43 This blotting action is capillary action. The same thing happens when you dry your hands. Have

00:22:49 you ever thought about that? You probably didn't realize that you were going through a bit of

00:22:53 capillary action, besides just drying your hands. You blot your hands with a towel. The towel has a

00:22:58 lot of capillaries in it, a lot of little pores, and the liquid runs into those pores and away

00:23:06 from your hands, and your poor little hands get dry. This capillary action is a common principle

00:23:14 in nature. In fact, Mother Nature uses it all the time. This is the process by which a liquid,

00:23:19 when going into the root of a plant, for example, can rise up to the top of the plant. The water

00:23:25 liquid proceeds up through the many hundreds and thousands of tiny little capillaries in the liquid

00:23:31 that is in the pores of the plant and rises up to the top. I think the process of rising up

00:23:41 through many, many tiny little pores can be illustrated over here by this next experiment.

00:23:45 In this experiment, we have another tube, not a capillary tube this time. You see,

00:23:55 a capillary tube is confined, that definition is confined to tubes having very tiny little

00:24:02 holes. This particular tube has a hole maybe a quarter of an inch in diameter, not at all a

00:24:08 capillary tube, but it is packed with a white solid, a very common white solid, which you will

00:24:14 find on your table every day, called table salt. Sodium chloride, for those of you who have been

00:24:19 fortunate enough to take a little chemistry so far. This wide tube, just an ordinary glass tube,

00:24:25 is filled with salt. I will pour a little bit of liquid into this tube, this dish to which tube

00:24:32 is attached. Capillary action taking place again. The blue liquid is rising. The dark liquid,

00:24:49 to me it's blue. The dark liquid is rising up the column of salt. The process is capillary

00:24:57 action again. The liquid makes its way around and in through the tiny little grains that are

00:25:04 packed into this tube. These tiny little grains are very small, so that the spaces between them

00:25:08 are very small, and the liquid likes to find its way up through these little spaces and will rise

00:25:14 as high as it can go. You might say, well how high can the liquid rise in the tube? Well, ask

00:25:21 yourself this question, what force is pulling on the liquid to come down? Gravity, the same thing

00:25:26 that keeps you and me on the ground. Well, the liquid can rise until the force of gravity causes

00:25:33 it to stop. Actually, in this particular tube, although this will not happen, that is the

00:25:40 liquid will not rise very high because the salt will dissolve in this water before that happens,

00:25:44 and probably the salt would fall out if we let it stand there. But the process by which the liquid

00:25:49 rises up through and around the tiny grains of salt is called capillary action. Now, we have

00:26:00 not said anything about what it is that makes a liquid rise up through a tiny hole. This we would

00:26:09 like to reserve for a later talk. Let me just throw the words out. The way in which a liquid

00:26:17 can rise up through a tube is dependent on its surface tension. Surface tension. We will have

00:26:23 more to say about that later. Different liquids have a different surface tension, and they'll rise

00:26:28 in a different way through tubes of different sizes. But the process is called capillary action.

00:26:35 Now, this is precisely the process by which the melted wax rises up through the string of the

00:26:45 wick, through the wick and gets up to the flame. So we've now illustrated the final portion of our

00:26:50 three parts of the flame, of the candle and its flame. Let's summarize here. We've introduced

00:26:59 Michael Faraday and his lectures in a small way, I think, of a chemical history of a candle. Michael

00:27:06 Faraday, that very famous chemist who lived over a hundred years ago, who liked very much to talk

00:27:12 to youngsters, and illustrated the principles of chemistry. He used a candle. The principles

00:27:20 that Michael Faraday used in talking about the candle are still operative today, even though we

00:27:26 now talk about jet planes and atom bombs and television. The same chemical principles apply.

00:27:32 They do not change because they are correct. The parts of the candle are the wax, the wick,

00:27:39 and the flame. The wax melts, a process called melting. The melted wax vaporizes. It is flammable.

00:27:50 We define flammable as something which will burn. The process by which the liquid changes

00:27:57 into a vapor is vaporization. We did not need the wick to cause the flame because we could

00:28:04 actually light, or the vapors could light themselves from the hot plate without the wick.

00:28:09 The process by which the wax rises up the wick of the candle is called capillary action. This

00:28:20 is an action which arises or which happens because there are tiny little pores. Actually,

00:28:28 the thing which is responsible for this is surface tension, which we would like

00:28:31 to discuss in another talk. Thank you.

00:29:20 This is National Educational Television.