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

00:00:22 AND THE LAWS THAT GOVERN, PRODUCED BY KQED SAN FRANCISCO, IN COOPERATION WITH THE CALIFORNIA

00:00:36 SECTION OF THE AMERICAN CHEMICAL SOCIETY, FOR THE EDUCATIONAL TELEVISION AND RADIO CENTER.

00:00:49 AND NOW LET'S GO TO OUR LABORATORY AND MEET DR. HARRY SELLOW.

00:00:55 Hello.

00:00:57 In previous talks, we've done a lot with experiments, not said anything about the men who developed

00:01:04 these experiments or who developed the laws and the principles behind these experiments.

00:01:10 In this talk, I would like to show you some experiments and the men who have thought first

00:01:16 along these lines.

00:01:18 Some famous men in chemistry and physics.

00:01:23 To begin with, I'd like to show you the first experiment because it will take some time

00:01:27 to progress and we can come back and look at it at a later point in the talk.

00:01:32 Here is an egg, a fine way to start a talk.

00:01:38 This egg has had the bottom shell removed so that the membrane present in the broad

00:01:44 half is exposed and has been dunked into water, that is the egg plus the exposed membrane.

00:01:49 In the top, by means of some ordinary candle wax, I stuck a straw.

00:01:55 This was prepared actually a couple of hours before this talk so that by now a liquid has

00:02:01 risen up the straw to almost over midpoint, well just about over midpoint where there

00:02:07 is a dark smear showing the fact that the liquid level is right there at the middle

00:02:13 of the straw.

00:02:16 When this experiment started, there was no liquid level visible in the straw at all.

00:02:19 It was down all in the egg, all down in the egg.

00:02:23 Since this has been going for about two hours, the liquid has risen up to this point where

00:02:27 I'm pointing.

00:02:28 We will mark that point and see just how far it can go, if any further, later in the talk.

00:02:38 I'll mark that one without trying to disturb the experiment too much.

00:02:43 There's a little tick mark right at the level of the liquid.

00:02:54 Chemistry and physics, or science in general, had its start of course generations ago, hundreds

00:02:59 of years ago, but we can track back to about the period of 1600 or thereabouts and pick

00:03:04 out some men, among many, who were instrumental in advancing science a great deal.

00:03:10 One of the first was a physicist and a chemist by the name of Sir Robert Boyle.

00:03:17 Robert Boyle studied the properties of gases.

00:03:22 Here is one kind of experiment he performed, or the principle illustrated by this experiment

00:03:27 was first, the principles were first illustrated by Robert Boyle in his experiments, we shall

00:03:32 try to do something of the same thing with modern equipment.

00:03:38 I have a jar sitting on a metal plate.

00:03:41 This plate has a hole in the center and is connected to a pump so that the air can be

00:03:45 removed from the jar.

00:03:46 In the top is a stopper to which is attached a piece of glass tubing, on the end of which

00:03:51 is a rubber balloon.

00:03:54 Now the balloon is now connected to this tank of gas so that when I open this up I can fill

00:04:00 the balloon full of compressed gas.

00:04:04 There is now, this jar is now filled with air.

00:04:07 I'll just do that, fill the balloon that is.

00:04:18 Here's the tubing connecting the gas to the rubber balloon.

00:04:24 Nothing up my sleeve.

00:04:26 There goes the balloon, being filled now.

00:04:52 The sound you heard just then was the balloon breaking in this jar.

00:04:57 The walls of the jar are pretty thick so that you don't get the loud noise of a balloon

00:05:02 breaking right out into the open air.

00:05:04 By the way, this is a bell jar, it doesn't have a glass bottom, the seal is made by putting

00:05:11 the jar on a flat metal plate and greasing the plate to provide the seal.

00:05:16 Now we'll replace the balloon, put another one in there.

00:05:26 This time, instead of blowing compressed air into the balloon while the bell jar is full

00:05:37 of air, the balloon will be inflated by withdrawing the air from the space around it.

00:05:47 In other words, a vacuum will be created around the balloon.

00:05:54 I've also cut off the air inlet to the balloon so that though it may expand a little it can't

00:06:02 expand very far, it doesn't have an air supply.

00:06:05 At the same time, connected to the top, that is connected to the piece of tubing which

00:06:11 holds the balloon, there is a T connection showing a vacuum gauge, and the vacuum gauge

00:06:16 will show the amount of vacuum which is present in the jar, or the gas pressure present in

00:06:22 the jar at any time.

00:06:25 I'll close off the valves here, make sure everything is tight, and now the pump starts.

00:06:42 Now I'll open the pump to the system.

00:06:53 So the pump is now withdrawing the air, taking the air out of the bell jar.

00:07:01 The balloon has inflated a tiny bit because there is air in it already, and since the

00:07:06 air pressure is being reduced around the balloon, the balloon will expand a little, but it cannot

00:07:10 get no more air other than what's in it.

00:07:13 Let's see what the vacuum gauge says.

00:07:14 There it is, down to about 12, 13 inches of mercury.

00:07:22 Atmospheric pressure is equivalent to a little over 30 inches of mercury, so that when we

00:07:27 get a vacuum on the gauge, which is a total vacuum, the gauge should read something a

00:07:34 little over 30, 30.4 or thereabouts.

00:07:41 Now down to 20, or up to 20 I should say, the air pressure is down.

00:07:47 The higher the gauge goes, the lower is the air pressure on the inside of the jar.

00:07:57 Notice as the vacuum gets better and better, or more and more complete, it's harder and

00:08:05 harder to get additional pumping.

00:08:08 The closer you get to the end, in a sense, the further you are away, or the harder it

00:08:14 is to get to the end.

00:08:16 Now it's 25, equivalent to 25 inches of mercury.

00:08:27 The pumping noise gets a little louder because now the pump is really laboring against a

00:08:33 partial vacuum.

00:08:42 And 26 inches, 26 and a half.

00:08:47 Let's see just how far this pump can go.

00:08:50 It probably will not reach 30 since this is not a real, really perfectly sealed system.

00:08:56 Rubber stopper, rubber to glass connections, very difficult to make a good tight seal.

00:09:02 There it is, to about 28.

00:09:07 That's about as far as it will go.

00:09:11 Now I'll shut the pump off.

00:09:23 Still just about 28, and slowly let air into the balloon.

00:09:37 This time the sound was less than it was before.

00:09:40 There was still a slight amount of sound because, I'll let all the air in now, can't hear myself.

00:09:48 There it is, zero vacuum.

00:09:51 The sound was less than it was before, there was still some sound because not all the air

00:09:56 was taken out of the jar so that sound could be transmitted.

00:10:01 The principle here then is this, sound must have some sort of medium in which to travel.

00:10:07 In this case, that is in the first case, the sound of the balloon bursting was carried

00:10:11 through the air to the sides of the balloon through the glass and out around us, around

00:10:16 to where we could hear it.

00:10:17 In the second case, since most of the air was evacuated, the sound could not be carried

00:10:22 as well.

00:10:23 If the air had been completely evacuated, all the way down to 30 and a little bit over,

00:10:27 we would not even have heard that little click.

00:10:31 This then was the sort of experiment that Robert Boyle first conducted in the study

00:10:38 of the gas laws.

00:10:39 Here is a picture of Robert Boyle, a rather handsome looking gentleman with a long flowing

00:10:49 wig.

00:10:53 It was his principles, it is his principles that are still being used in the study of

00:10:58 gases today, the effect of pressure on gases.

00:11:02 Let's go on and look at the next famous man in our little series, Sir Isaac Newton.

00:11:11 Before we talk a little bit about Newton, I would like to start this experiment, which

00:11:14 will illustrate one of the principles he first described, by this little boat.

00:11:19 Here is a boat constructed out of a soap dish, a couple of pipe cleaners, an old leftover

00:11:27 aluminum cigar wrapper, and two little candle stubs placed underneath the boat.

00:11:34 Just light the little candles underneath the boat.

00:11:39 One, two.

00:11:46 This is a two candle power jet boat.

00:11:54 Now, while this little boat is warming up, I'd like to point out a few of the things

00:12:02 that Sir Isaac Newton and all his brilliant genius worked on.

00:12:06 Of course, in those days, you must remember that a scientist did not restrict himself

00:12:12 to any one field of interest.

00:12:14 All science was considered the province of the good scientists.

00:12:18 Sir Isaac Newton is a wonderful example of this type of individual.

00:12:22 Perhaps let's just jot down a few of the things he was interested in.

00:12:31 He was a good astronomer.

00:12:32 He studied a lot about the movement of the solar system and the planets therein.

00:12:38 So he was interested in astronomy.

00:12:42 Here he worked out the law of universal gravitation, by which we understand today the forces governing

00:12:48 the motion of our heavenly bodies.

00:12:51 He studied mechanics, or that part of physics having to do with the motion of various bodies,

00:13:02 applying to the motion of molecules as well.

00:13:04 This is where his interests would overlap those of chemists, who also concern themselves

00:13:10 with the motion of molecules.

00:13:12 He made fundamental discoveries in the study of light.

00:13:16 It was Sir Isaac Newton who first discovered that a beam of white light, when shined through

00:13:22 a triangular piece of glass, a prism, could be separated into its component colors.

00:13:30 He also made great and significant contributions to mathematics.

00:13:38 In fact, Sir Isaac Newton is quite often thought of as a mathematician, practically, before

00:13:42 he's thought of as a physicist or a chemist or an astronomer.

00:13:46 In mathematics, in working out these motions of bodies and the action of light, in the

00:13:52 mathematics he invented a form of calculus, which we study today.

00:13:57 Well, let's see if our little boat has gotten on yet.

00:14:02 In the cylinder, I placed a little bit of water, I should say, about a third full.

00:14:10 The back of the cylinder has a little hole punched in it, a tiny little pinhole, enough

00:14:17 to let trickles of steam escape.

00:14:20 The back end has been taped on by this light tape.

00:14:23 There it goes, it's now developing a head of steam.

00:14:25 I'll leave it at that angle so you can see the steam shooting out from the little pinhole

00:14:30 against this dark background.

00:14:31 That chalk floats, too, my doggies.

00:14:34 Get it out of there.

00:14:36 Turn this around.

00:14:40 And away goes our little jet boat.

00:14:42 The steam is really pushing it around.

00:14:44 Of course, as it moves, the flames of the candles wave a little bit so that they don't

00:14:50 get directly under the body of the...

00:14:54 It's really ejecting steam now, moving right along.

00:14:59 Let it spin itself here.

00:15:04 The principle being illustrated is this.

00:15:08 First, I should say, explained by Sir Isaac Newton.

00:15:13 The candles are causing steam to form on the inside of the little boat.

00:15:17 This steam is escaping through the hole in the back of the boat.

00:15:24 I'll get it back here where it can be seen again.

00:15:33 So that in escaping, the boat gets pushed forward.

00:15:39 Well, here's the principle.

00:15:40 First, as I say, explained by Newton.

00:15:43 As the steam is ejected in one direction, it imparts a force in the opposite direction

00:15:49 to that which is ejected, just exactly equal and opposite to the main force, to the first

00:15:56 force.

00:15:57 This is Newton's third law of motion, that every action has an equal and opposite reaction.

00:16:04 Just as in firing a bullet from a gun, the bullet, in leaving the gun, imparts a recoil

00:16:10 to the gun so that you feel the slap against the shoulder.

00:16:13 This is the principle by which a rocket, for example, would travel through space.

00:16:18 There is fuel and oxygen on the inside of a rocket.

00:16:20 The two combine to form a tremendous hot blast of gas being ejected out of the end of the

00:16:26 rocket.

00:16:28 This blast, in coming out of the rocket, would push the rocket forward.

00:16:33 Now there's a common misconception here, perhaps.

00:16:37 The steam does not have to impinge against the air or hit against the air around the

00:16:41 boat.

00:16:42 The fact that the steam is blasted out of the back of this little boat is enough.

00:16:47 That force pushes the boat forward.

00:16:51 Every action has an equal and opposite reaction.

00:16:55 Newton's third law of motion.

00:16:57 Let's just bring the boat over here once more and let it travel the full length under its

00:17:00 own steam.

00:17:01 There she goes.

00:17:05 Everything is burning.

00:17:08 Pipe cleaners are about out of water now, it's out of its fuel.

00:17:11 Well, the jet boat.

00:17:15 Let's put out the fire.

00:17:23 Here is a picture of Sir Isaac Newton about the height of his fame.

00:17:31 Very distinguished man, indeed.

00:17:37 Let's go on then and look at the third of our famous men in this talk.

00:17:43 To do the next experiment, we'll have to start the pump, so I'll just make the connection

00:17:48 here.

00:17:52 Here is a balance, right at this moment, pretty close to exact balance, on which there are

00:18:01 weights and some equipment.

00:18:03 The equipment consists of a small candle on a piece of foil, a glass chimney, and a tube

00:18:09 containing an absorbent material, which I'll explain in a moment.

00:18:14 Right now, if I just touch the balance, it will go a little bit out of balance and then

00:18:17 return to center point because it's been exactly balanced, or very nearly that.

00:18:23 It swings just about three divisions or so to either side and centers itself, perhaps

00:18:30 a little trifle heavier on the side of the weights.

00:18:34 The point is this, as the experiment progresses, one side or the other will become heavier

00:18:38 depending on how this experiment works out.

00:18:40 Let's see just how the thing does happen.

00:18:43 Now a first pump.

00:18:47 The pump is drawing air through this tube, through the absorber, and then out of the

00:18:54 chimney.

00:18:55 Air can get in on the underside of the chimney.

00:18:58 I will light the candle.

00:19:07 And put the chimney over the candle.

00:19:22 It should still be in balance, or very close to it, just like it was before.

00:19:25 It's a little, tiny, tiny bit heavy on the side of the weights.

00:19:30 Now the candle is burning in the chimney, the gases, if there are any gases being formed

00:19:35 or vapors that escape out of the chimney are sucked through the absorber and go into

00:19:41 the pump.

00:19:44 This experiment, or an experiment of this type, was first performed by a very famous

00:19:49 chemist, indeed a French chemist this time, the other two were English, Antoine Lavoisier.

00:19:57 It is Lavoisier who was given the credit for the start of modern chemistry.

00:20:03 He performed the first, most accurate experiments involving balances, much more accurate than

00:20:08 this particular one as a matter of fact.

00:20:11 At the time Lavoisier lived, there was a theory being advanced by very famous men, equal in

00:20:17 stature to Lavoisier, equal in fame.

00:20:20 There was a theory being advanced, excuse me, the candle wants to go out a little bit,

00:20:25 perhaps the suction of air is too great, let me see if I can just pinch this off a little

00:20:30 bit, there we go, there's a little bypass here which bleeds a little air into the pump

00:20:38 to make up for what the candle isn't getting, there, there it is, takes a little adjustment.

00:20:43 I was talking about Lavoisier, he first performed this kind of an experiment.

00:20:47 Now notice that the pointer already is a trifle over on the side toward the candle and away

00:20:56 from the weights.

00:20:57 It's actually on the other side of center, indicating that the side with the candle is

00:21:01 getting heavier.

00:21:02 This in spite of the fact that the candle is burning down.

00:21:08 How is it possible that the candle should be disappearing yet that side of the balance

00:21:12 is getting heavier?

00:21:13 Lavoisier was the one who explained this.

00:21:16 He pointed out, contrary to the theory of that day, that when a substance burns, it

00:21:20 gains weight, that is, picks up oxygen from the air.

00:21:25 In the case of the candle, the candle picks up oxygen, forming carbon dioxide and water.

00:21:31 That carbon dioxide and water is caught in the absorber.

00:21:35 If you didn't catch it in the absorber, it would escape out into the air and actually

00:21:40 that side of the balance would get lighter, and this was the mistake that the men made

00:21:43 in the early days.

00:21:44 They didn't watch carefully all of their weights.

00:21:47 Lavoisier did this very accurately and very carefully and pointed out this matter of combustion.

00:21:54 And now it is indeed a little heavier on that side.

00:21:57 I'll just jar the balance to see how it works here.

00:22:01 It's actually wiggling back and forth, but it is heavy on the side of the candle, indicating

00:22:07 that the candle plus its products are heavier than when they started.

00:22:11 I'll just blow the candle out, it's gone far enough, and turn the pump off.

00:22:23 Here's a picture of Lavoisier, father of modern chemistry, especially modern analytical

00:22:27 chemistry.

00:22:29 Let's go on then in time.

00:22:32 We are now to the period of about 1790, around the 1800s.

00:22:37 Lavoisier has been killed in the period after the French Revolution, actually beheaded because

00:22:44 unfortunately some people didn't realize the importance of such a man and he was guillotined.

00:22:49 It was indeed unfortunate.

00:22:52 Well, the next experiment will illustrate the observations of two scientists, actually.

00:22:58 One, a man who first performed this experiment without fully realizing what was done, and

00:23:04 the second, the man who explained it and really got the full impact of it.

00:23:08 Here is a vacuum tube in which there is a screen.

00:23:12 By means of this vacuum tube and this magnet, we will illustrate some of the properties

00:23:17 which led to the discovery of the electron.

00:23:19 To do this, I'll put the shield over the tube so that it can best be seen, and if we can

00:23:27 have the lights off, please.

00:23:29 Why?

00:23:30 There.

00:23:31 We'll see this experiment a little better.

00:23:34 I'll now cause a voltage to be imparted across that tube from one end to the other.

00:23:38 Watch what happens.

00:23:48 There is a streak of light going from this electrode to the other electrode.

00:23:58 That beam can be affected by a magnet.

00:24:02 Let's put a magnet right up against the glass and wiggle it around and see if something

00:24:06 happens to the beam.

00:24:09 I am now moving the magnet up and down.

00:24:11 The beam is also moving.

00:24:13 The magnet, of course, is on the outside of the tube.

00:24:16 Now, this means that there must be an electrical particle or particles traveling through the

00:24:22 tube because only such particles or such bits of electricity in moving would have a magnetic

00:24:30 field which could be in turn affected by a magnet.

00:24:34 If these were not electrical in nature, they would not be affected by a magnet.

00:24:37 This tube is called a Crookes tube, Sir William Crookes being the first man who observed it.

00:24:44 If we can have the lights back on again, we'll go on to the next type of tube and look

00:24:47 at this further.

00:24:51 This is a beam of electrons that we saw going across the screen, working exactly the way

00:24:57 the electrons work in the vacuum tube of your TV set.

00:25:02 Electrons running across this screen, which is made of zinc sulfide, leave a light trail.

00:25:06 That trail of light, I should say, can be seen.

00:25:09 To more properly see this or more easily see this, let me switch the electrodes to

00:25:13 the next type of Crookes tube and see if we can get a direct observation of the effect

00:25:17 of these electrons.

00:25:21 The man who first really explained this, the things that happen in a Crookes tube, and

00:25:28 the man who is credited with the discovery of the electron is an Englishman by the name

00:25:33 of Sir J.J. Thompson.

00:25:36 Here is an example of the study that Sir J.J. Thompson made when he explained the electrons

00:25:42 flowing through here.

00:25:43 There.

00:25:44 There's a little paddle wheel here running on a glass track.

00:25:48 That paddle wheel ran across the tube as if it were being bombarded by some sort of particles,

00:25:53 and indeed it was.

00:25:54 If I reverse the electrodes, I can make the paddle wheel travel in the opposite direction.

00:26:00 Still bouncing around in there.

00:26:01 See if I can get it to go all the way across the other side.

00:26:03 I now cause the beam to come from behind the paddle wheel all the way to the other end.

00:26:09 That paddle wheel shows that there are particles having weight bouncing against it, otherwise

00:26:14 it could not move.

00:26:17 Indeed an important discovery.

00:26:18 Let's go back now and look at our first experiment to see just what happened there.

00:26:23 Oh, by the way, I have here a picture of Sir J.J. Thompson, which I can show you.

00:26:35 There he is, the gentleman here with the glasses.

00:26:38 Sir J.J. Thompson.

00:26:42 Now, the experiment we started at the beginning of the talk was the experiment with the egg.

00:26:48 We made a mark on the level of liquid in the egg.

00:26:53 Here is the mark.

00:26:55 The dark region, which was formerly, the top of the dark region was formerly at the mark.

00:27:00 Now the bottom of the dark region is at the mark.

00:27:02 So the level of liquid has moved up about an inch or an inch and a half.

00:27:06 This process of liquid diffusing through the membrane of an egg is called osmosis.

00:27:12 Osmosis, O-S-M-O-S-I-S.

00:27:17 And the level of liquid rising up in the tube is due to the fact that the water in the jar

00:27:23 got up into the egg through the membrane, filled up the egg because the liquid in the

00:27:26 egg couldn't go back the other way, the egg got filled, the liquid rose in the straw.

00:27:31 The straw is put in through a hole in the top of the egg.

00:27:34 The gentleman who first observed this important physical principle, which describes the motion

00:27:38 of many liquids in the human body, was Professor Jacobus van't Hoff, a famous physical chemist.

00:27:47 Here is a picture of Professor van't Hoff, kind of a wild hair looking individual, yet

00:27:52 a very pleasant, intelligent man who inspired many students.

00:27:59 Well, who are the men that we talked about today in our Chemical Hall of Fame?

00:28:07 The famous men we discussed were van't Hoff, Boyle, Newton, Lavoisier, Thompson, and a

00:28:15 little tiny bit about Sir William Crookes.

00:28:18 Thank you.

00:28:48 This is National Educational Television.