Freshman Organic Chemistry I

CHEM 125a - Lecture 19 - Oxygen and the Chemical Revolution (Beginning to 1789)

Chapter 1. The Predecessors of Chemists: Alchemists [00:00:00]

Professor Michael McBride: So we know something about all these powerful tools that had been developed: quantum mechanics around 1925, ‘26 actually; and then all these much more modern things, including scanning probe microscopy, which is really quite recent. But the most powerful tool in organic chemistry, for everyday practice, and certainly for anybody who’s not a professional chemist and into quantum mechanics and stuff like that, is bonds; this amazing invention of bonds, and how people knew what things were like before any of these tools were dreamt of. Right? And, for that, we go back in time and look at these guys in the nineteenth century who invented it. And we begin with what’s called — whoops — we begin with — sorry, here we go again — okay, we begin with the Chemical Revolution. Right? That’s a name that historians of science have given this period, beginning with Lavoisier. So really that’s where we’ll start. But he didn’t just spring from nowhere. There was a long tradition of some kinds of chemistry before that, and we’re going to just review that very briefly. There’s a background in ancient art and lore. Okay? So, for example, here’s a mosaic from Montreale, in Sicily, of Noah, as making wine and then falling victim to it and having his shame hidden by his sons. Okay? And here’s his flask, right?

Student: Oh no.

Professor Michael McBride: This is like 3000 years ago. The mosaic is about 1000 years; it’s twelfth century, it’s 800 or 900 hundred years old. Okay? Here is a Roman glass perfume vial, that’s 2000 years old. So they made perfume, obviously, and extracted the stuff from flowers and whatever that would do that. Okay? There’s the Chemical Research Building when it was five days old. Okay? And we already saw Francis Bacon who said: “All the philosophy of nature which is now received, is either the philosophy of the Grecians, or that of the alchemists.” So the alchemists are in a sense our ancestors. He didn’t have a very high opinion of them. He said: “The one is gathered out of a few vulgar observations” (that’s the Greek philosophers) “and the other out of a few experiments of a furnace. The one never faileth to multiply words, and the other ever faileth to multiply gold.” So even at this time, when science was beginning to get underway, modern science, alchemy was already in disrepute. But it did contribute some things. It didn’t contribute much to theory, because the theory depended on Greek, well on the Greek antecedents and authority, rather than observation. But they did fiddle around. Here’s a painting of an alchemist from 1663. And remember, Newton did more work in alchemy than he did in physics. Right? And he wrote an enormous amount but never published anything about it. There’s a great website now, from the University of Indiana, of all Newton’s alchemical works, and you can look at them.

But this was to be kept a secret. That was the idea of alchemy, that it was occult, it was hidden. Okay? And in fact there’s a show that’s coming up on alchemy at the Beinecke Library, in January, of their holdings in alchemy, and the title of the show is “The Book of Secrets.” Right? And that’s Harry Potter as well, right? [Laughter] So here’s one of the things that’s going to be shown. It’s part of a really long scroll, which is the Visio Mystica of Arnold of Villanova, who was a thirteenth century alchemist who was into medicine and was considered the greatest medical authority of its time. This particular scroll was written in England in 1570. So a lot of it’s in English. It says, “the red sea, the red lune [the red moon], the red sol [the red sun].” Right? All sorts of mystical things. And then, and you see here is the corpus, the body, which is earth; and here’s the soul, which is oil; and here’s the spirit or the air, the breath, which is water. So there was — everything was a symbol for something else. Or if you look at the four corners of this, on the bottom right we have air. Right? “Eeyre,” it says, “is hott and moyst.” Right? Or on the top left is earth, which is cold and dry; the opposite of air. And down here is fire, which is hot and dry. And up there is water, which is cold and moist. Right? So this was supposed to be something profound and mysterious.

Another thing they’re going to show is this book, On the Philosopher’s Stone, which was written in the thirteenth century. The particular copy they have is from 1571. But it looks like somebody’s organic chemistry text, after they’ve highlighted it in preparation for the exam. Every word is underlined. [Laughter] Right? And all in the margin are these fingers pointing to important things. Right? And if you look there, you’ll see great words like alchemy there, you see elixir. I forget, there are a lot of key words. But fundamentally it’s all nonsense, all the theory. The reason people kept it secret, really, was, I think, not to keep other people from finding it out, but to hide the fact that it was nonsense. That’s just my own theory, so maybe that’s wrong. Okay, but Paracelsus, in the early 1500s, was an alchemist, a traveling physician, and he developed what had been long before that, which was the Doctrine of Sympathies, and one aspect of that was in nature, antidotes for poisons are to be found near the source of the illness. Right? So, for example, you know what that is?

Student: Poison ivy.

Professor Michael McBride: Poison ivy. Right? But near poison ivy you’re likely to find jewelweed, which is an antidote for poison ivy. Right? Or — poison ivy is a New World thing, so that didn’t interest the alchemists — but this one certainly did. Willow — Salix is the Latin name for willow — which is found in malarial swamps. So you go into a swamp, you get malaria, but you also find the willow there. And the willow bark, extracting from the willow bark you can get Salicin, a glycoside, which is a sugar plus an aromatic thing there. Right? And if you hydrolyze that to get the sugar off, and oxidize that to make a carboxylic acid, you get this. What’s that?

Students: Salicylic acid.

Professor Michael McBride: Right. Salicylic acid, from alix. Right? So it’s good for fevers and so on, for your malaria. Okay, so that’s a theory. This is another thing they’re going to show, a Vade Mecum — come along with me — which is a lab manual that was kept by Caspar Harttung vom Hoff, in 1557, in Austria. So you can see he draws various — what he’s, he’s reading various things, and writing extracts and notes to himself about it. It’s like your pre-lab preparation. Right? Okay, and you notice who he’s quoting up here? Arnold, that guy from the thirteenth century who did the thing we’ve showed first. Right? Arnold of Villanova. Okay, but he shows distillation apparatus. These things are called pelicans. Isn’t that interesting? And here’s a lamp. And here’s somebody, he’s filtering something through some kind of screen or grid there. Okay? So they developed tools that were of great use to chemistry, once chemistry got going. So there was a lot of — even though the theory was nonsense — there was a lot of practical background in preparing various elixirs and so on. So this was crucial.

Chapter 2. Scheele’s Acids and Elements [00:08:51]

Now here is a lab that could easily be mistaken for an alchemical laboratory, but in fact it’s an early chemical laboratory. And I’ll show it to you here. It’s this book, it’s this picture here from 1777, from a book about Air and Fire. And it reports the discovery of a new element, in this book. And it’s by Carl Wilhelm Scheele, who was in Uppsala; “Upsala,” in Sweden. What do you think he discovered with light and fire — or pardon me, with air and fire; Luft und dem Feuer?

Student: Oxygen.

Professor Michael McBride: Ah ha, we’ll see. So that’s his laboratory, Scheele’s laboratory, or at least some artist’s impression of it. And here he is. He’s before the Chemical Revolution, but he’s an important precedent, as you’ll see, to the Chemical Revolution. He was by practice a pharmacist but he spent most of his time doing what is really chemical research. Here’s a picture of a stamp, a Swedish stamp, showing Scheele. Except it’s not Scheele. It turns out the costume he’s wearing wouldn’t have been developed until forty years after Scheele died. Okay, but he purified organic compounds, that weren’t easy to purify; in particular, carboxylic acids. So he got an acid from — that he called lactic acid; which we now know has that structure. Where did he get it?

[Students speak over one another]

Professor Michael McBride: From sour milk. Okay? So here’s his paper about that, “On Milk and its Acid” from 1780. So he purified these acids as salts that he could crystallize. That was the method of purifying. So here’s several reports in that paper. Item 7: “Bismuth, cobalt, antimony, tin, mercury, silver and gold were attacked by lactic acid, either by digestion” (that’s just sitting there under it) “or by boiling. After standing over tin, the acid caused a black precipitate to form in a solution of gold and aqua regia.” Right? So this is not mysterious writing. Right? It’s talking in language that we can understand, even though it’s translated from German. Iron and zinc were dissolved with a formation of flammable air. What do you suppose — he reacted acid with zinc and he got flammable air. What do you suppose that was?

Student: Hydrogen gas.

Professor Michael McBride: Hydrogen, right? “The iron solution was brown and gave no crystallization, but the zinc solution crystallized.” Why was that important?

Student: He could purify it.

Professor Michael McBride: Because he could purify it if it crystallized, and get just that salt. Right? So that’s how he got pure samples of acids. Right? “With copper, our solution first took on a blue color, then green, finally dark blue, but did not crystallize”; unfortunately. And 10: “Lead dissolved after several days of digestion. The solution acquired a sweet, tart taste,” [laughter] “but did not crystallize.” Right? So what do you do when you don’t have IR and NMR, right?

Student: Eat.

Student: Taste.

Professor Michael McBride: Sure. So he tasted all these things. Cyanide too. Okay, so he got citric acid. Where did he get that?

Student: Lemons.

Professor Michael McBride: From lemons, okay? And he got uric acid; obvious. He got tartaric acid. Tartaric acid, his discovery, turns out to one of the — probably the single most important, maybe the second, no probably the most important compound in the nineteenth century, as you’ll see. Okay? That comes from tartar, which is the deposit on the inside of wine casks, after you’ve fermented wine. Okay? Benzoic acid came from gum benzoin, a product of the Far East. Okay? And oxalic acid. Where do you think that came from? It came from rhubarb. Now why oxalic; why oxy? Oxy means sharp. So what does sharp have to do with it, with rhubarb?

Student: It has a sharp taste?

Professor Michael McBride: Yes, so you know oxy as a root, meaning sharp. Oxymoron doesn’t mean a stupid ox. What it means is sharp, and moron means dull. So it’s a sharp dullness, is an oxymoron. It’s a self-contradictory word. Right? So what’s sharp about rhubarb?

Student: Its taste.

Professor Michael McBride: Its taste; it tastes acidic. In fact, the word acidic comes from the Latin acidus; which comes from acre, to be sour; which comes from, the root is ac, which means sharp. So it’s the same thing, acid and oxy. Okay? So look at all these things. They have what? The carboxylate group, which makes them acidic. Right? And we know why it makes it acidic; this is a review from last time, this functional group. It’s not a carbonyl alcohol, it’s a carboxylic acid. The high HOMO is stabilized in the acid. But it’s even more stabilized when it’s an anion, because you have a higher HOMO. So it changes the acidity, the ease of dissociation of H⁺, by a factor of 10¹¹th. Right? Which depends on the energy difference between those two. So if you more stabilize the anion product than you stabilize the starting material, then you shift the reaction toward product, here by 10¹¹th; a big change. Okay? But actually there’s more to it than just that resonance, just that HOMO/LUMO interaction. There’s a thing called “inductive effects” that we’ll talk about later on. But a large part of it is due to that.

Okay, but you notice there’s one exception here. Uric acid doesn’t have a carboxylate group in it. So there’s what it has. And notice that it has an unshared-pair on nitrogen. Like an amide, it’s stabilized by a carbonyl; in fact, it’s stabilized by two carbonyls, two adjacent LUMOs to stabilize it. Now if that were just stable, it wouldn’t be a reason to get rid of it, to lose a proton. But the anion that you get if you lose the proton from nitrogen has a higher HOMO. So it’s even more stabilized. The same trick as in carboxylic acid, but even more so, as you’ll see here. The pK_a of this compound is 5.8. It’s pretty acidic. Right? But a normal amine, like ammonia losing a proton, has a pK_a of 38. Right? So this is thirty-two powers of ten helped out, because it has such a high HOMO on the nitrogen, and two carbonyls to stabilize it. Okay, so uric acid is indeed an acid, like carboxylic acids.

Okay, now Scheele not only did these organic acids, he also discovered, or co-discovered, seven elements. They’re listed here according to what row of the periodic table they’re in. Notice down at the bottom here you have tungsten. Right? Tungsten comes from Swedish. He was Swedish. It’s “tung” “sten,” heavy stone. Being way down, it’s got lots of protons and neutrons and is very, very dense. Right? So it’s heavy — the stones that it comes from are very heavy. Right? But by contrast, these up here are gases. And in fact that’s what got the 19th Century chemistry going. That’s what launched the Chemical Revolution, was the ability to work with gases. Because to be a gas, something has to be a small molecule and therefore simple, or at least relatively simple. So you had to start with simple things before you could get the complex ones, like salicylic acid, in terms of understanding.

Now Scheele, in 1771, had heated silver carbonate, and he found that he got CO₂ out of them; he didn’t know it was CO₂, but the gas came out. Okay? And if you heated that still more, greater than 340 Celsius, then you get silver, and oxygen comes out from silver oxide; this gas, this feuerluft, fire air. That’s what the book is about. Okay? So he wrote the book. But the book starts, as I’ll show you here — sorry, there we go — the book starts with an introduction, a “vorbericht,” which is translated, it says, from Swedish. And let’s see where it says here. And it’s by Torbern Bergman, written in 1777. He had this book written for two years, waiting for this preface to come. Bergman was a busy guy. Right? And during the time that this book was sitting, ready, the manuscript was sitting ready to be printed, Priestley, in England, discovered oxygen. So this book came out after Priestley. But there’s no doubt that Scheele had discovered it earlier. His lab books from 1771 show it. And here, in 1774, is his draft of a letter that he wrote to France. And it begins — or it actually begins with a couple of words on the previous sheet — but it says: “…since I have no large burning glass, I beg you to try with yours…” Because he had to do this by heating things in an oven, at a really high temperature, which was hard to do. But if you could do it with a focused light of the sun to heat it, then it would be much more practical. And, in France, they had such a big magnifying glass, that would allow to do it. But that letter, although it was sent, was never answered. And you know who it was sent to, presumably. Lavoisier, the founder of the Chemical Revolution, and another discoverer of oxygen. Okay?

Chapter 3. On Radicals, Lavoisier, and the Chemical Revolution [00:19:58]

Okay, so now we’re going to talk about Lavoisier, who was — wasn’t a perfect person, but he was really very, very good. Okay, now the Chemical Revolution. You can say it started in 1789, the Chemical Revolution. And that’s not the only revolution that started in France in 1789. Right? Do you know what this is? What?

Student: Tennis Court Oath.

Professor Michael McBride: It’s the Tennis Court Oath, when the legislators, so to say, gathered to say that they wouldn’t disband until the king granted them certain things; and you know what that led to, in 1789. The only guy that didn’t agree was this guy here. He’s the only one that didn’t sign it. But at any rate, it was radical. Now there’s an Indo-European word, that’s the root of many words, called Werad; and it gives words in all sorts of languages. Like it means root. Okay? And Wurzel, in German, means root; and wort, like St. John’s wort, is a root. Licorice; glukos rhiza, Greek, the rhiza is root; sweet root it means. Okay? Race; razza in Italian is the root of your being. Right? Rutabaga. Radix in Latin; and you know lots of words come from radix, like radish is a root. Or eradicate, what does that mean?

[Students speak over one another]

Professor Michael McBride: It means to pull it out by the roots. Okay? Or radical; something that’s radical is something that goes right to the root, back to the very origin of something. And that word, used in that way, if you look in the Oxford English Dictionary, it was coined in mathematics in the 16th Century. The root of a number is its origin. Right? If you take the square root of a number, and multiply it by itself, you get the number. So it’s the root of the number; the radical. Right? Or in politics, it was used in 18th Century in England, and in chemistry, in 18th Century in France, the idea of radical as the root of things, began to be used; which we’ll see.

Okay, so 1787, radical was introduced as a political term, according to the Oxford English Dictionary, by J. Jebb, whoever he was; presumably a politician. Or in 1787, there was this radical document, “We the People.” Right? But that same year, 1787, radical was introduced as a chemical term, by Louis Bernard Guyton de Morveau. And it was in the context of developing nomenclature for chemistry. So he, together with Berthollet and Fourcroy, developed a new method for nomenclature in chemistry. And here’s a book. This is not the original French, but it’s the first English translation, which you see comes from the Yale University Library, back when. It’s from 1788. Okay? So A Method of Chemical Nomenclature, by Guyton de Morveau, Lavoisier, Berthollet and Fourcroy. So the fourth author of this new method of chemical nomenclature is Lavoisier. So there’s Lavoisier with his wife. This is part of an enormous picture that’s in the Metropolitan. It was commissioned by Lavoisier and his wife, who hired Jacques-Louis David to paint it. And they paid 7000 pounds, to the artist to paint it; which is the equivalent of $300,000 today. They were quite well-to-do. They had an income of the order of a million dollars a year, or the equivalent; it depends on how you translate numbers, of course. It’s hard.

So here he is at the age of 45, in 1789, and he’s working on drafting — so these guys, when they had their portraits painted, always put something important in it. So what did he choose to have? He chose to be working on a manuscript, and the manuscript he’s working on is the manuscript of this book, from 1789. It’s called Traité Élémentaire de Chimie; the Elementary Treatise on Chemistry. And the other stuff he put in the picture is the equipment he used. So here you see various equipment from one of the plates at the end of the book. And you can see these items in the picture. There’s that bell jar. There’s that device. There’s that big sixteen-pint flask, with a brass fitting on it. There’s that valve that you attach to the bottom of the flask. And over here is a portfolio, and the portfolio says, down in the corner, “Paulze Lavoisier sculpsit.” That means this was drawn by Paulze Lavoisier, who was his wife. She was his assistant in the laboratory, kept all the notebooks; read English for him, because he couldn’t read English. So if he had to do anything with Priestley, she would read it to him. But she drew all these things. She studied with David, drawing, in order to be able to do this. Okay, she painted this portrait of their family friend. Who’s that?

Student: Benjamin Franklin.

Professor Michael McBride: Yes, Benjamin Franklin. I showed you that picture earlier, said we’d refer to it again. So this is that particular plate in the book, and it relates to weighing a gas. It’ll turn out that the most important thing for Lavoisier, and for the whole 19th Century — all this development that led to bonds and their arrangement — weighing was the key thing. But how do you weigh a gas? So you need gases so they’re simple enough to deal with, and easy to purify. Right? But you need to weigh them. So how can you weigh a gas? Well you can collect a gas, as shown in this picture, by generating it in this retort G, and it comes and it bubbles up, displacing water or mercury, most often mercury, from a bell jar. You’ve done this kind of thing?

Student: Yes.

Professor Michael McBride: Some of you. But you can see how it would work; as it bubbles up the mercury comes down. Okay. So now you have the gas. Now we’ll shift attention down to the bottom right here, and see how this works. So we have this bell jar on the bottom, which is fitted with valves on the top, is filled with mercury, and it’s in a pool of mercury, and then this big sixteen-pint flask is evacuated. You use one of these pumps. Remember, 100 years before this, Hooke — or 130 years before this — Hooke made a great vacuum pump for Boyle. Boyle is the only person on the front of the building older than Lavoisier. Right? And that was dealing with gases and Boyle’s Law, how pressure and volume relate to one another. Okay, so anyhow, he could evacuate that with a pump, then seal it off, turn the valves off. And he’s got mercury in that thing. And now he puts a tip underneath it and generates gas. And it bubbles up and fills this container with a gas. And it’s sitting in a mercury pool so that it’s not communicating with the atmosphere, other than through the pressure, through the mercury pool.

Okay, so now he opens the valves. So the vacuum starts sucking up the mercury; that is, pulling the air in, up to a certain point. Right? Then the mercury stops rising. Okay? And now, at this point you know that the pressure of that gas is atmospheric pressure, less whatever the height of the mercury column is. Right? That’s how a barometer works. So he knows how much gas, what volume of gas he has in A. He filled it with water first and weighed it to see what its volume was. Now he knows the volume, he knows the pressure. So he knows how much gas there would be, at atmospheric pressure. Right? And now, of course, he just turns off these things, unscrews one, the thing on top, and weighs it, and sees how much heavier it is than it was when it was evacuated. And that’s how much the air weighs. And he knows how much volume, how much pressure. So he knows how much whatever gas he collected weighed. So he could weigh a gas. Pretty clever, huh? Okay, here he is working with one of these bell jars. Now these bell jars were filled with mercury. I don’t know if you’ve — here, would you help me out Wilson? Lift this up and show it to the class. But don’t lift it high, hold it above the thing. Did it surprise you?

Student: Yes.

Professor Michael McBride: He said it surprised him. And you can come up afterwards, if you want to, and be surprised yourself, by lifting this up. But keep it over this, because people are so panicked about mercury nowadays. I heard on the way over to class, while I was bringing this, I heard there’s a new law in the European Union that it’s going to be illegal to transport mercury over international borders. Go figure. Anyhow, there’s Lavoisier doing an experiment with this big thing of mercury. Right? He must’ve been a stout person. Okay? This is him in his library, with Madame Lavoisier taking his dictation, as he does his experiments.

Chapter 4. The Elementary Treatise of Chemistry: Facts, Ideas, and Words [00:29:55]

Okay, so here’s the Traité Élémentaire de Chimie, and I’ll show you the — this actually is a facsimile, not the real thing. But here’s the title page of the first volume. Okay. So you can look at that if you want to. And at the end, I’ll just note here, at the end of the second volume, are all these pages, which are devices — like here’s this is the one we just looked at. Okay? So if you want to look at them, feel free. Don’t handle the other one though; it’s real.

Okay, so Elementary Treatise of Chemistry, Presented in a New Order — this is the Revolution — According to Modern Discoveries, With Figures; as I just showed you. And 1789 is the date, the same as the French Revolution. Okay, you notice he’s a member of all different academies, including Philadelphia. Why in the world would he have been a member of the Scientific Academy of Philadelphia? He never went there.

Student: Ben Franklin was —

Professor Michael McBride: Right, his pal. Okay, 1789. So it has the most wonderful Introduction, called “Discours Préliminaire.” And he says: “My only object, when I began this work” — or, “I had no other object when I began the following work, than to extend and explain more fully the memoir, which I read at the public meeting of the Academy of Science in the month of April, 1787” (remember when radical was introduced and so on) “on the necessity of reforming and completing the nomenclature of Chemistry.” So that’s all he was trying to do was get a proper nomenclature that would be useful, in contrast to all this alchemical nonsense. Okay? “While engaged in this employment, I perceived, better than I had ever done before, the justice of the following maxims of the Abbé de Condillac and his System of Logic and some other works.” So this is what Condillac said.

“We think, only through the medium of words. Languages are true analytical methods. Algebra, which is adapted to its purpose in every species of expression, in the most simple, most exact, and best manner possible, is at the same time a language and an analytical method. The art of reasoning is nothing more than language, well arranged.”

So Lavoisier goes on to say:

“Thus, while I thought myself employed only in forming a Nomenclature, and while I proposed to myself nothing more than to improve the chemical language, my work transformed itself by degrees, without my being able to prevent it, into a treatise upon the Elements of Chemistry.”

So in the process of reforming the language, he reformed the whole understanding of the science.

“The impossibility of separating nomenclature of a science from the science itself, is owing to this, that every branch of physical science must consist of three things; the series of facts which are the object of the science, the ideas which represent these facts, and the words by which the ideas are expressed. Like three impressions of the same seal, the word ought to produce the idea, and the idea to be a picture of the fact.”

So all these things have to be harmonious. Right? Three impressions of the same seal.

“And, as ideas are preserved and communicated by means of words, it necessarily follows that we cannot improve the language of any science without at the same time improving the science itself; neither can we, on the other hand, improve a science, without improving the language or nomenclature which belongs to it. However certain the facts of any science may be, however just the ideas we may have formed of these facts, we can only communicate false impressions to others, while we want words by which these may be properly expressed.”

Right? So clarity, as opposed to obscurity, was his goal; as opposed to Newton or the alchemists. Right? Facts, ideas and words, and they all have to tie into one another as impressions of the same seal. Okay? So he presented things, as he had advertised, in a new order; very different from any book on chemistry that had been written before. First was doctrine, — that is, the theory — the first part of the book, which is a two-volume book. So almost all of the first — no, about two-thirds, I think, of the first volume are doctrine. And then nomenclature; that’s what he had set out to do. And finally operations, how you can actually repeat this stuff for yourself, what devices you need. Of course, he was very wealthy and could employ people to manufacture all the equipment he needed; not everybody could do that. But he showed exactly how it was done and gave great — it’s easy to understand exactly what he did. Now, one of the first things he turned his attention to was elements. He says:

“…if by the name elements we mean to designate the simple, indivisible molecules” (molecule just means little thing, right?) “that make up substances, it is probable we do not know what they are.” (They’re just too small. Right?) “But if, on the contrary, we associate with the name of elements, or the principles of substances, the idea of the furthest stage to which analysis can reach, all substances that we have so far found no means to decompose are elements for us… they behave with respect to us like simple substances.”

So it’s an operational, not a philosophical, definition of element. If you can’t break it apart, consider it an element until you can break it apart. We have elements here, the chemical elements. Are they elements, according to Lavoisier’s definition? Like here we see cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium. Are they elements, according to Lavoisier?

Students: No.

Professor Michael McBride: Why not?

Students: You can break them.

Professor Michael McBride: You can break them apart, into nuclei and electrons. The nuclei you can break apart into protons and neutrons, and you can break these things apart into quarks and so on. But, for Lavoisier, or for chemists, those are elements, because you don’t break them apart. Okay?

Chapter 5. New Nomenclature: Elements, Calories, and Radicals [00:36:52]

So here’s a table of simple substances, in the first English translation of the Traité Élémentaire de Chimie. So here’s a table of the elements: “Simple substances belonging to all the kingdoms of nature, which may be considered as the elements of bodies.” So what are the first two elements, things that you can’t break apart?

Student: Light.

Professor Michael McBride: Light and heat are the first two elements — which we don’t see in Mendeleev’s table, right? Because they’re fundamentally different from the other elements, because they don’t have any weight. You can weigh a gas but you can’t weigh light, and you can’t weigh heat. Okay? So he gives new names to these things — light and caloric — and what the old name was. Light used to be called light too, but in his new system he’s going to keep the old name; or “caloric”, he’s going to use for what used to be called heat; or “the principle or element of heat”; or “fire”; or “igneous fluid”; or “the matter of fire or heat”. Those were terms people had used before, but he’s going to call them “caloric”. Okay?

Now, if you have caloric, you must be able to measure it. If you can’t weigh it, what you can do; you can use a “calorimeter” to measure it. And this is the calorimeter manufactured and used by Lavoisier; and also Laplace, a younger man who was his colleague, who became a great mathematician, as you probably know. So here’s the thing. It’s big. That’s a three-foot rule. So this thing stood this high off the table, right? Okay? Now here’s what it is. There’s a lamp that’s going to make fire. There’s oil in the well of the lamp. You’re going to measure how much heat you get out of burning that oil. So you put it inside this bucket, and you put the bucket in this mesh cage and put the lid on. Then you put that cage, and its lid, up into this can. Okay? And now you light the flame, in there. You want to measure how much heat it gives. How do you measure the heat? What you do is surround it by melting ice. So the heat will melt the ice. Now there’s going to be a problem. Obviously the more heat, the more ice you melt. But that’s not the only place heat’s coming from. Where else will it come from, to melt the ice?

Students: Outside.

Professor Michael McBride: From outside. So this is where the thing is clever. So there’s another can, outside that can, and you fill it with ice, which is an insulator, for the inside. So no heat comes from the — any heat that comes from the outside, melts the outside ice, not the inside ice. Only the flame will melt the inside ice. Okay, and notice that the lids also are covered with ice too. So it’s completely surrounded by ice, and then by another layer of ice. So your flame burns, burns, burns, burns. And you fill — water comes up as they melt in both of them. And then you put that thing underneath and turn the tap, and see how much water was melted; only by the flame, right? And that measures how much heat. Pretty clever, huh?

Okay, so that’s a fact, is measuring how much heat there is. But analysis in general is it. This is from the Oxford English Dictionary, which Yale has a subscription to. So you can look up words to your heart’s content. It’s a lot of fun. This year is the 80th anniversary of the Oxford English Dictionary. There was a symposium, down the hill, sponsored by the library, including the guy that wrote that The Professor and the Madman. Has anyone read that book about the Oxford English Dictionary? It’s a wonderful short book, and the madman was a Yale graduate. Really, it’s an interesting story. And the other guy was one who read the Oxford English Dictionary, cover to cover, 20 volumes, within one year. He wrote a book about that, during the last year. It was a fun thing. But anyhow, this is — it’s fun to look up things in the Oxford English Dictionary. And here’s analysis. So you see it comes from ana, and I think it’s lisein; but I can get some help on that.

Student: luein.

Professor Michael McBride: luein, okay. Anyhow, but it means “to loose,” according to the Oxford English Dictionary. So it’s to loose back; to take things apart is the sense of it. And generally it’s the resolution or breaking up of anything complex into its various simple elements. So you can analyze a passage in literature. Okay? It’s the opposite of synthesis. Okay? “The exact determination of the elements or components of anything complex; specifically in chemistry, the resolution of a chemical compound into its proximate, or ultimate, elements.” Now, proximate and ultimate, what does that mean? You can see down in the historical uses of it what proximate and ultimate mean. 1791, this same time — 1789, remember, was the Traité Élémentaire — said, “the quantity of charcoal, which something yields by analysis.” So you find out how much charcoal is in it. That’s the word — we now say carbon. So that’s elemental analysis. That’s ultimate analysis; take things all apart to the chemical elements, see how much of each one. But there’s also this thing called proximate analysis, which you can see from this quote in 1831. “Sugar, starch and gum are proximate principles, and these we obtained by proximate analysis.” So you can take some foodstuff and see what percentage of protein, what percentage of sugar, or what percentage of this, that and the other thing. So what you read on a candy bar, or something like that, that’s proximate analysis, not elemental, not ultimate analysis. So both kinds are important in Lavoisier’s work, as we’ll see.

Okay, so we looked at light and caloric. Now let’s look at a few of these elements, the ultimate elements here. He had the fact, the theory and the word for these things. So how about Azote? Why is that word — that’s the French name for — the French still call nitrogen azote, and in this English translation it was called that in 1790 or ‘91. Okay, where does that word come from? What does the prefix a mean?

Student: Without.

Professor Michael McBride: Without. And how about zo? It’s great we have somebody taking Greek.

Student: Life.

Professor Michael McBride: Without life. In what sense is that an appropriate name, a meaningful name for nitrogen? Alex?

Student: I think they performed the tests on nitrogen first and it was —

Professor Michael McBride: What kind of tests?

Student: They would suffocate like a bird in nitrogen.

Professor Michael McBride: Yes, if you put a mouse in an atmosphere of nitrogen, it’s azote. Right? So that’s what the name meant. It used to be called phlogisticated air, or gas, or mephitis, or the base of mephitis. Right? Azote is the name that Lavoisier decided to use for it. Or hydro-gen. How about it, help us out?

Student: Hdor would’ve been water.

Professor Michael McBride: Pardon me?

Student: Water.

Professor Michael McBride: What about water? Hydro is water. What’s gen?

Student: To leave water.

Professor Michael McBride: It makes water. Right? So if you burn hydro-gen, you generate water. Right? So hydrogen. Okay. How about oxy-gen? What does it generate?

Students: Acid.

Professor Michael McBride: Acid, sourness. So oxygen is the element that generates sourness, that generates acid. And that is the key element in Lavoisier’s theory, the oxygen theory of combustion. Okay, so oxygen, plus a base, or radical — right? So these two terms meant the same thing to Lavoisier, the fundamental radical, the root of some substance, right? And you react it with oxygen and it makes the stuff into an acid. Can you think of an example of an element that you react with oxygen and it becomes an acid? Well let’s just look in his table. Sulfur; you burn it and it becomes sulfuric acid, or sulfurous acid. Right? Phosphorous generates phosphoric acid. Carbon generates carbonic acid. Muriatic radical — which we don’t know; they haven’t discovered the muriatic radical yet, the base of that acid — but if you burn it and combine it with oxygen, you get muriatic acid. Does anybody know what muriatic acid is?

Student: Hydrochloric acid.

Professor Michael McBride: Hydrochloric acid. How much oxygen is in it?

Student: None.

Professor Michael McBride: None, right? But that was the theory, that you take a base, you react it with oxygen, you get an acid. So there must have been a muriatic radical. Okay? Unfortunately that part of it was wrong. The same for fluoric radical. Okay? But then there were also compound radicals, radicals that were only proximate, not ultimate; radicals that had several other elements in them. Right? And here were some of those, a list of those radicals, with the names that Lavoisier decided to use for them. And many of them, all the ones indicated by an arrow, are ones that Scheele had already discovered; like tartaric, citric, oxalic, benzoic, lactic. Lithic acid was another one that I didn’t mention before, which comes from stones; see, it’s from urinary calculus. Okay, so those were compound radicals. And that’s the end of today’s lecture.

[end of transcript]

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