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

00:00:25 AND THE LAWS THAT GOVERN, PRODUCED BY KQED SAN FRANCISCO, IN COOPERATION WITH THE CALIFORNIA

00:00:39 SECTION OF THE AMERICAN CHEMICAL SOCIETY, FOR THE EDUCATIONAL TELEVISION AND RADIO CENTER.

00:00:52 AND NOW LET'S GO TO OUR LABORATORY AND MEET DR. HARRY SELLOW.

00:00:58 Hello.

00:00:59 In this talk, I'd like to show you some of the properties of an element which is both

00:01:04 one of the most common elements on earth and at the same time one of the most rare.

00:01:10 Let's make a little bit of that element.

00:01:15 Pour a little bit of cane sugar in the cylinder, about 200 milliliters, a little bit more

00:01:29 here, moisten it, that ought to be about wet enough, wait until that water soaks down

00:01:51 to the bottom, and now pour in about an equal amount of sulfuric acid.

00:02:18 The reaction has started almost at once.

00:02:28 The black material which is rising in the cylinder is the element of which I speak,

00:02:35 carbon.

00:02:37 Here we formed carbon by the reaction of concentrated sulfuric acid with sugar.

00:02:44 Sugar is a compound composed of carbon, hydrogen, and oxygen.

00:02:48 The sulfuric acid is able to withdraw the hydrogen and oxygen from the sugar, leaving

00:02:53 behind the carbon.

00:02:56 The fumes that are coming out are actually fumes of decomposed sulfuric acid.

00:03:01 They're very pungent, sulfur dioxide, quite pungent.

00:03:06 This black material is carbon.

00:03:11 Let's look at another common way of making carbon.

00:03:14 Here's our old friend, the candle, put the flame to burning a little bit.

00:03:31 In one of our earlier talks, we talked about the properties of candle, in fact had quite

00:03:35 a bit to say about it, and even illustrated this kind of formation that we're about to

00:03:40 look at again.

00:03:42 If I take a white surface, such as the bottom of this dish, and hold it over the candle

00:03:47 flame, taking care not to lean over the first experiment, the candle flame will deposit

00:04:00 our element on the bottom of the dish.

00:04:06 And there it is, quite sooty.

00:04:09 This black material is carbon.

00:04:13 Again, carbon is being formed by the reaction occurring in the flame of a candle.

00:04:21 The candle is composed of wax.

00:04:25 The wax is a compound of carbon and hydrogen.

00:04:29 When this compound burns, one of the products that's formed is ordinary carbon, a very fine

00:04:36 powder called soot.

00:04:38 Basically it is because the candle flame is a very inefficient type of burning unit

00:04:43 that carbon is deposited.

00:04:46 Carbon like this is made commercially by a very similar process.

00:04:50 Instead of using candles, actual gas flames are used, but a yellow flame will deposit

00:04:54 carbon on a surface in which this carbon is going to be collected.

00:04:59 This carbon can then be scraped off and used commercially.

00:05:03 It has many uses.

00:05:04 Let's look at one of the uses of carbon powder like this in the next experiment.

00:05:11 Here is a cylinder of this carbon powder.

00:05:15 Actually it's not as fine a powder.

00:05:17 These are little chunks of carbon, but the cylinder has been packed full of this type

00:05:22 of carbon.

00:05:24 I have here some water which has been darkened by the use of a little bit of ink.

00:05:33 I'll pour this in the cylinder.

00:05:44 The ink solution is now in the top here, percolating through the carbon.

00:05:49 Give it a little time to get down through it, and now let me collect a little sample

00:05:54 of this liquid.

00:05:58 There, it's coming through right now.

00:06:13 About all of that that I put in just went through.

00:06:19 Look at the difference in the color of the two solutions.

00:06:25 The dark ink solution is still, of course, quite dark, while the material which ran through

00:06:33 has come out essentially colorless.

00:06:35 There is a slight tinge to it.

00:06:36 I ran it through kind of fast, but it's essentially colorless.

00:06:40 The color has been removed from the water.

00:06:43 This process goes by a very complicated name.

00:06:47 Removal of color is called decolorization.

00:06:51 It's very complicated.

00:06:56 D-color-i-zation.

00:07:03 See, the chemist doesn't play very many tricks.

00:07:06 He just makes several little words into one long word to remove the color from.

00:07:13 This is a commercial process.

00:07:15 Actually, one such use as this is the one in the manufacture of cane sugar,

00:07:21 the type of sugar that we just demonstrated in the first experiment.

00:07:24 You see, in preparing pure white cane sugar, it is sometimes true that the sugar gets colored,

00:07:31 brown sort of, like a dark sugar in the manufacturing process.

00:07:35 In order to get pure white crystals from these, at one point during the process,

00:07:39 darkened solutions of sugar are poured through beds of charcoal just like this.

00:07:46 Dark sugar goes in and light-colored or colorless solutions come out.

00:07:50 Then the colorless solution can be evaporated and the white sugar crystals recovered.

00:07:55 We talked about just this process in connection with another experiment we did earlier in an earlier show,

00:08:00 and that was the use of a gas mask.

00:08:02 You see, in a gas mask there is also carbon.

00:08:06 The carbon has the property of soaking out on its surface undesirable gases.

00:08:12 Here the carbon is soaking out on its surface the coloring matter in the solution.

00:08:17 This we gave the special name adsorption in a previous talk.

00:08:22 The same thing is working here too.

00:08:24 The carbon has the property of having stuck on its surface the undesirable material.

00:08:31 Well, let's go on and look at just what is the structure of these various kinds of carbon of which we've been talking.

00:08:38 Here is the carbon powder.

00:08:40 It looks very much like a powder, of course.

00:08:44 This would be what the carbon would look like if a large portion of the material on the bottom of the white dish were collected

00:08:51 or scooped out of that cylinder in which we made carbon in the first instance.

00:08:56 No particular form to this carbon, just amorphous carbon having no definite structure.

00:09:02 I've written that word on the board, by the way, amorphous, meaning having no definite structure.

00:09:10 There are, however, two other forms of carbon which are very common.

00:09:15 The first, well, besides the amorphous carbon, graphite is a common form of carbon.

00:09:23 Here I have a picture in this book of the structure of graphite, that is, a picture of how its atoms are arranged.

00:09:33 In graphite, the carbon atoms are arranged in layers or in plates,

00:09:39 each plate of carbon atoms being stacked above the other plate.

00:09:45 The essential features are that in each layer the carbon atoms are close together,

00:09:51 but there is a great distance between successive layers.

00:09:54 So here you have one flat plate of many carbon atoms, let's say,

00:09:58 and then my hand would represent the second plate of many carbon atoms,

00:10:02 but the two plates are separated by some distance.

00:10:05 This gives a graphite a peculiar property.

00:10:08 It gives it the property which makes it a very good lubricant for one thing

00:10:12 and a good material to use in lead pencils.

00:10:15 See, lead pencils are not really lead pencils, they're graphite pencils.

00:10:18 When you write with a pencil, what you're doing is causing these layers to be rubbed,

00:10:23 one against the other, and layers are being wiped off on the paper.

00:10:28 In many uses, as a lubricant, you see, ordinary oils would decompose under great heats,

00:10:36 just as might be caused if two large blocks of metal were rubbing against one another

00:10:40 in a gigantic stamping machine, one which would stamp out car tops, automobile tops.

00:10:46 Well, you'd want to lubricate a surface like this,

00:10:48 but it's difficult to do it with an ordinary oil because that oil would burn up due to the friction.

00:10:52 Graphite, in this instance, is a perfect lubricant.

00:10:55 It can be thrown into the space between the metal blocks,

00:10:59 and these can be rubbed around together and will slide around easily

00:11:03 because the layers of graphite will rub on each other very easily.

00:11:08 The last form of carbon, which is the rare form,

00:11:11 accounting for the rarity of carbon while the previous forms were more common, is the diamond.

00:11:18 Diamond has a structure all its own.

00:11:20 It has a diamond structure, and this is what the chemist means by the diamond structure of carbon.

00:11:28 In a diamond, the carbon atoms are not arranged in layers as they are in graphite,

00:11:33 but they are closely packed.

00:11:36 They are arranged at the corners of a peculiar figure in space having four sides.

00:11:44 This is called a tetrahedron.

00:11:46 Tetrahedron, a four-sided figure.

00:11:49 Each carbon atom has as its neighbors four other carbon atoms.

00:11:53 Here is a picture of a tetrahedron on this next page.

00:11:58 And each are equally spaced from the other and at an equal angle.

00:12:02 All the angles are equal, one carbon atom from another.

00:12:06 This is the structure of carbon in diamond,

00:12:09 This is the structure of carbon in diamond,

00:12:11 and it turns out that this is the preferred structure that carbon takes in almost all of its compounds,

00:12:17 about which we will have something to say both in this talk and the next one,

00:12:21 and looking at some models as well.

00:12:23 The result of this type of structure is that it gives diamond a very hard property.

00:12:29 It can cut almost any other element or any other material.

00:12:34 Also, a diamond being essentially pure carbon or very pure carbon,

00:12:39 why, if it were to be burned, would leave no ash, would completely burn to carbon dioxide.

00:12:46 That is one of the ways of testing whether you have a pure diamond, by the way, is just to burn it.

00:12:50 If it leaves no ash, the diamond is pure.

00:12:53 It's a very expensive test, however.

00:12:56 Here are some models of the structure of carbon compounds.

00:13:03 Here is methane. This is carbon surrounded by four hydrogens.

00:13:08 The tetrahedral form again, you see.

00:13:10 Carbon at the center.

00:13:13 I'll remove a hydrogen atom.

00:13:15 Carbon at the center, and four hydrogens at each corner of this four-sided figure, the tetrahedron.

00:13:22 Each hydrogen atom equally spaced from the carbon and from the other hydrogen atoms.

00:13:27 The CH4 combination is the formula for methane.

00:13:32 You see, all the hydrogen atoms are arranged the same way,

00:13:36 so this model can be tipped in any direction and it always looks the same.

00:13:45 Still another compound of this same type of structure, only with different atoms along with carbon, is carbon tetrachloride.

00:13:51 The name gives away the structure.

00:13:53 Carbon followed with four chlorine atoms.

00:13:56 Notice that in this particular model, the carbon at the center is smaller by proportion than each of the chlorines.

00:14:05 This model is built in exact proportion to the actual molecule.

00:14:09 Carbon surrounded by four chlorine atoms.

00:14:11 Again, this can be tipped in any direction.

00:14:13 Tetrahedral carbon, four-sided.

00:14:17 And finally, here is a more complicated one of a complicated model of a very common compound, ethanol.

00:14:24 Also known as ethyl alcohol.

00:14:27 Here we have carbon atoms joined up with hydrogens around the carbon atoms.

00:14:32 At the same time, there is an oxygen atom also stuck onto this model,

00:14:37 showing that the ethanol is composed of carbon, hydrogen, and oxygen.

00:14:42 This cannot be turned around without looking different in all directions because of this combination of oxygen and hydrogen.

00:14:49 This is what gives ethanol its particular properties.

00:14:52 We'll have more to say about this kind of property in the next talk.

00:14:55 These then are compounds formed with carbon combining with other elements.

00:15:07 Let's look at some of the properties then of some compounds containing carbon.

00:15:18 I'll pour a little water into this test tube.

00:15:22 And use a little bit of this material.

00:15:42 If I can get some out of here.

00:15:46 Let's get a nice fresh piece.

00:15:52 Throw this into the water.

00:15:56 Vigorous reaction right away.

00:16:02 Now let's see if this is really a compound of carbon.

00:16:07 It certainly is.

00:16:12 Flamed due to the burning of the gas, which is being liberated by the reaction of this compound with the water.

00:16:20 I want to keep this tightly capped because no water should get into the can.

00:16:25 This is calcium carbide.

00:16:30 The calcium carbide reacts with the water in the test tube and forms a familiar compound of carbon known as acetylene.

00:16:39 The acetylene, of course, is flammable, that is, will burn, which is one of the properties of many carbon compounds.

00:16:46 Burns with a very sooty flame, as you can see, the soot is right around the test tube.

00:16:53 In fact, can be used for that purpose, that is, for a flame. We'll have a word to say about that here in a moment.

00:16:59 Well, it's all done, the reaction's over.

00:17:02 There's a milky white solid in the water solution.

00:17:08 Carbon and the solid.

00:17:11 What is the reaction that occurs when calcium carbide reacts with water? Let's write that one on the board.

00:17:22 Calcium carbide is CaC2.

00:17:28 This reacts with water, and I'll write water as HOH.

00:17:33 It's just another way of saying the same thing, that is, H2O or HOH.

00:17:37 This is more like the actual structure of water.

00:17:40 These two react, then.

00:17:43 Acetylene is formed, which is C2H2, plus the white solid, which is calcium hydroxide.

00:17:54 Ca with the group OH, parentheses, taken twice.

00:17:59 Calcium hydroxide is lime.

00:18:02 Now, if we put a two in front of this, the chemist will feel very happy, because now the equation is balanced.

00:18:10 It means that a molecule of calcium carbide reacts with two molecules of water.

00:18:15 Proportions are right.

00:18:17 A molecule of acetylene is formed, and a molecule of calcium hydroxide is formed.

00:18:24 This particular compound, that is, calcium carbide, used to be called miner's lamp.

00:18:29 In fact, the can here says miner's lamp.

00:18:32 That gives away one of its most common uses, years ago, as a source of light in a mine.

00:18:38 The miner used to wear a cap that had this little acetylene lamp on it,

00:18:42 and if he put a little water into this lamp, why, it would react with the carbide,

00:18:48 and acetylene would be given off, which could be lit, and would light up the area.

00:18:53 In the old-time automobiles, their headlights used to be made so that the light was obtained from this same material.

00:19:01 Also, acetylene is used, in combination with oxygen, as torches to cut through steel.

00:19:08 Acetylene-oxygen torches at very high temperatures are obtained.

00:19:12 Let's go on, then, and look at properties of some more compounds of carbon.

00:19:19 I'll put a little piece of paper on top of each one of these glass cylinders.

00:19:25 By the way, the paper itself is a compound of carbon.

00:19:28 Actually, carbon, hydrogen, and oxygen.

00:19:31 Cellulose.

00:19:33 Now, I'll sprinkle a little bit of this liquid on each of the papers.

00:19:46 Got enough of it here.

00:19:48 First on this.

00:19:51 And then on this.

00:19:53 Let's put a little more back here.

00:19:57 This particular liquid evaporates rather readily.

00:19:59 It has a very disagreeable odor, smells kind of like rotten eggs.

00:20:05 It is now evaporating from the papers.

00:20:11 Taste it a little bit here.

00:20:17 Almost all gone.

00:20:30 A woofer and a tweeter.

00:20:33 Low note and a high note.

00:20:36 It just went on the floor. It's extinguished. No danger.

00:20:40 The solution I used here was a solution of phosphorus in carbon disulfide.

00:20:46 Here is the structure of carbon disulfide, or rather, its formula.

00:20:50 This is a solution of phosphorus in carbon disulfide.

00:20:54 The compound of just those two elements, of course.

00:20:57 Carbon disulfide is very flammable.

00:20:59 Well, what happened was this.

00:21:02 The solution of carbon disulfide evaporated.

00:21:05 That is, the carbon disulfide evaporated from the solution,

00:21:08 leaving behind the phosphorus, which was dissolved in that solution.

00:21:12 As a result, the solution of carbon disulfide evaporated from the solution,

00:21:17 leaving behind the phosphorus, which was dissolved in that solution.

00:21:20 As soon as all the carbon disulfide was gone,

00:21:23 the phosphorus immediately reacted with the oxygen in the air,

00:21:27 and the result produced a lot of heat,

00:21:30 which caused the paper to catch fire.

00:21:34 The instant the paper caught fire,

00:21:36 why, the carbon disulfide vapors,

00:21:38 which had leaked down into each cylinder,

00:21:41 because they're heavier than air,

00:21:43 these carbon disulfide vapors immediately caught fire themselves.

00:21:47 And giving that heat,

00:21:48 they caught fire themselves.

00:21:50 And giving that sound of that particular explosion.

00:21:54 There is a sort of white deposit on each one of these cylinders now,

00:21:58 showing that some sulfur was also formed in this reaction.

00:22:04 So this is another compound of carbon that has interesting properties.

00:22:07 Let's go on then and look at still one more.

00:22:13 I'll pour some of this liquid

00:22:16 in one of the beakers.

00:22:19 Looks like about enough.

00:22:23 And here, I'll put a...

00:22:25 Both of these are compounds of carbon, by the way.

00:22:28 This one, the one I just poured, is calcium acetate,

00:22:32 a solution of calcium acetate.

00:22:34 This is ethanol,

00:22:36 the same molecule that is the same material

00:22:38 which I showed the model of in the early part of the talk.

00:22:42 And this one,

00:22:44 the one I just poured,

00:22:45 the same molecule that I showed the model of in the early part of the talk.

00:22:48 I'll pour some of this ethanol in the other beaker.

00:22:55 Both liquids.

00:22:57 A little more, perhaps.

00:22:59 Both compounds of carbon.

00:23:02 Now I'll mix the two.

00:23:04 Watch what happens.

00:23:07 Whoops.

00:23:09 Doesn't want to pour anymore after the first mixing.

00:23:12 A solid material has been formed.

00:23:15 At least a material which looks pretty solid.

00:23:17 It won't fall out of the beaker, certainly.

00:23:19 Let's fish out a little bit of it.

00:23:24 Very jelly-like.

00:23:26 Thick and jelly-like and a little gooey.

00:23:29 I'll put a little bit out here on the pad.

00:23:33 And see if it's flammable.

00:23:48 It's very difficult to see.

00:23:50 It's a very pale, luminous flame when it is burning.

00:23:52 I think it's burning right now.

00:23:54 Let's test it and see if it is.

00:23:56 I'll hold this paper over it.

00:23:57 It certainly is.

00:24:03 Try it again.

00:24:09 And it's just about...

00:24:14 through burning.

00:24:16 In fact, it's difficult to see.

00:24:18 The flame is hardly visible.

00:24:20 And it's just about gone out right now.

00:24:23 Let's see what happens.

00:24:24 And it's just about gone out right now.

00:24:29 It certainly has.

00:24:32 This compound that I formed was the peculiar gel-like material.

00:24:39 See, here is saturated calcium acetate.

00:24:42 Now, calcium acetate is a salt which is soluble in water.

00:24:45 This is a saturated solution of it.

00:24:47 It's quite liquid.

00:24:49 It has a little extra undissolved calcium acetate in it.

00:24:51 Solution in water.

00:24:52 The calcium acetate together with the alcohol...

00:24:56 Well, let me put it this way.

00:24:59 Calcium acetate is soluble in water.

00:25:02 But it's not soluble in alcohol.

00:25:04 When you throw alcohol in the saturated solution of calcium acetate,

00:25:08 the calcium acetate is precipitated out.

00:25:10 But at the same time, while this is precipitated out,

00:25:13 the calcium acetate solid soaks up the alcohol just like a blotter would

00:25:18 and forms this thick, gooey gel.

00:25:20 So here we have solid calcium acetate which is full of ethyl alcohol.

00:25:26 This is what gives it that flammable property.

00:25:29 In fact, this particular material is commonly known as canned heat or sterno,

00:25:34 a material which is familiar to most of you who have done any outdoor living.

00:25:39 You can use this as a source of fuel.

00:25:41 The alcohol burns with a very clean flame,

00:25:44 and having the calcium acetate with it makes it a solid

00:25:47 which can be handled very easily.

00:25:48 So it's not really a chemical reaction, you see.

00:25:51 The calcium acetate has soaked up the alcohol into it,

00:25:55 and the resulting compound then will burn.

00:25:58 Well, what have we learned then about the compounds of carbon and its compounds, rather?

00:26:05 We made some carbon in the first experiment

00:26:10 by the reaction of sugar with sulfuric acid.

00:26:13 We also showed that this carbon had a property called decolorization.

00:26:19 That is, it would decolorize materials which were colored.

00:26:22 Here was one such combination.

00:26:25 That is, we had a solution of ink which we could pour into this column of charcoal.

00:26:32 The ink would be actually soaked out on the surface of the charcoal,

00:26:37 and the clear water, that is, the colorless material, came from it.

00:26:40 The charcoal and the clear water, that is, the colorless material, came through.

00:26:44 Here it is, ink solution before pouring in,

00:26:47 and the clear solution after it came through the bed of charcoal.

00:26:50 This process was called decolorization, removing the color of.

00:26:56 We then looked at the structure, pictures of the structure,

00:27:00 of various forms of carbon, the three forms,

00:27:03 ordinary carbon, graphite, and diamond,

00:27:06 plus models of actual carbon compounds,

00:27:10 methane, carbon tetrachloride, and ethyl alcohol.

00:27:14 We then went ahead to look at some of the reactions of compounds of carbon.

00:27:20 We made some acetylene by the reaction of calcium carbide with water.

00:27:25 The acetylene was flammable, burned with a very yellow flame,

00:27:30 deposited a lot of carbon as a consequence of its burning.

00:27:32 We showed two interesting little explosions due to the fact that carbon disulfide,

00:27:37 another compound of carbon, is also flammable.

00:27:42 And finally, we demonstrated that calcium acetate,

00:27:47 a compound of carbon, in solution,

00:27:50 would soak up ethyl alcohol, also a compound of carbon.

00:27:54 The two together formed a very spongy, viscous, gel-like material,

00:27:59 which could be used as a fuel.

00:28:02 This fuel is called canned heat, or sternal,

00:28:06 and is used commercially in chafing dishes at home,

00:28:10 perhaps camping outings, and so forth.

00:28:14 These then were carbon and its compounds.

00:28:17 Thank you.