Our next topic will be the history of chemistry, and Joy Hakim has several relevant chapters in her book, The Story of Science: Newton at the Center, including two chapters on Lavoisier. As my long-time students will remember, Hakim’s text is full of errors of various kinds — philosophic, historical, and scientific, mostly of a casual nature because she is a journalist, not a scientist, but worth noting as a kind of lesson in what kinds of errors are out there all the time. It is very difficult to write a text, as I well know; errors creep in all the time. Still, it seems that if the Smithsonian is behind this book, they could come up with a better proofing job. Regardless, here is my suggested proofing. I’ve tried to write it so it’s interesting and useful even if you don’t have her book. Fact is that these are the things lots of people get wrong.
Hakim critique, chapter 25 on Lavoisier
As usual, Hakim chooses an important scientist – Lavoisier — and she covers the themes that go with him, but her writing is full of errors of various kinds.
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Since the topic is Lavoisier, probably the most important thing is to get a good definition of chemistry going, but it’s hard because you sort of have to know a lot about chemistry to define it well. That’s why she opts for a definition that calls it the study of the “stuff” of which the universe is made.
Yes, chemistry is the study of matter, as are all the natural sciences, and it’s the branch which goes to the bottom of what is familiar, things like gold and silver, wood, water, and air, just before matter dissolves into electrical charges and we turn from chemistry to physics. In terms of ooms, (if you don’t know what that is, try the given link or ask me in class) chemistry deals with #10, and then with #9, and maybe #8, though I don’t know if there are any molecules in the #8 other than from living creatures – so that’s really biochemistry.
Hakim places Lavoisier’s research in the context of the American Revolution by mentioning George Washington and several other contemporaries who, she says, followed his work and were in touch with him about their own doings. Certainly Benjamin Franklin was a revolutionary hero with an international scientific reputation. The relevance of this association is a little clearer on the next page. Not much.
But first, Hakim has to emphasize the exactitude of Lavoisier’s records. Exactitude is important; the natural sciences are studies of the material world, and they do require disciplined observation, though I will say that, as presently taught, the business of keeping records can be a fetish that obscures science instead of revealing its nature.
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Here we have an image and description of the distillation process. Hakim says it is a matter of boiling water (or any liquid) then capturing and cooling it. Of course what you have to do is move or position the captured vapor into some space such that when it cools and condenses, it drips into a new container. The pelican-shaped container in the upper left corner of the illustration does just this — water vapor goes up the neck because it naturally rises. But the neck also conducts the vapor off to the side so that when it reaches the top and cools, it drops into a different bucket.
…and Gnosticism
Having asserted the importance of exact measurement, Hakim has a disclaimer in the margin, to the effect that no measurement is exact. Well, lots of measurements are exact, because lots of measurements deal with integers, but even those that involve long and irrational decimals are of scientific value if they are exact enough to answer the question at hand. It’s a little gnostic to go around saying that “there’s no such thing as an exact measurement.”
What do I mean by that? Gnostic ideas are roundabout ways of being snobbish about how perfectly you recognize that knowledge is impossible, and how much right you have to look down on people who think they know something. Gnostics have a sense that neither God nor the world can be known; but this is opposed to our faith as children of a Father Creator, with our minds made in his image. What happens when people become gnostic is that they stop studying because they are discouraged and think it is useless. So gnosticism (spelled with a capital when it’s religious: Gnosticism) is bad for culture.
Finally, there’s this description of a famous experiment in which Lavoisier was able to show that water had not become earth but had simply broken off bits of glass. My, my! What was he boiling that would break off bits of glass? I must presume that his vessels were something a little more like clay or a poor grade of ceramic!
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It was Cavendish who discovered hydrogen, and who discovered that burning hydrogen caused it to combine with oxygen and form water. It was well done for Lavoisier to repeat the experiment and draw the conclusion that water was not an element, and that this had implications for the whole concept of elements; and he did get the privilege of naming hydrogen.
Oxygen notes: Yes, oxygen is the most common element in the crust of the earth. Most of the sands of the world are quartz, which is SiO2, a silicate with two oxygen atoms for each atom of silicon. Much of the remaining rock is an aluminum silicate (feldspar) which has some aluminum and some other things and then about 2 oxygen atoms for each one of the other elements. That’s why oxygen is so common in the crust of the earth, more common than in the air — though you can’t breathe it!
Ozone is not relevant to this chapter, but anyway, it’s a molecule with three oxygen atoms, and, the molecule not being very happy about the extra oxygen, it’s always ready to offload one. It is, therefore, very reactive and that’s why it can oxidise/burn/damage stuff.
If you look at the timeline in the lower corner of this page, you will note that Lavoisier and Herschel were born just one year apart. Herschel lived much longer, of course, since he didn’t get his head cut off in the French Revolution. He lived in England, for one thing.
If you didn’t look at the timeline, let that be a lesson to you. Timelines are useless when they have too much information on them, but if you trust the author, you will stop and notice some of the people who were contemporary with your latest hero, or who may have contributed to his insights.
Use the timeline. And make useful ones when it’s your turn.
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Hakim indicates that Lavoisier distinguished elements, compounds, and mixtures. This is a very important insight: Some materials cannot be divided into other materials; these are elements: gold is elemental. Others can be divided into elements very different from the compound, as shells, which are calcium carbonate, can be divided into oxygen, carbon, and calcium, none of which, on its own, looks or behaves like a shell. Still other things can be sorted, rather than cut or divided into their parts – for example, air can be sorted into oxygen and nitrogen and a few other things; it’s a mixture of various gases.
…Corroded metals
Hakim’s picture of corroded metallic objects is very pretty in its own way, but the surrounding textbox is a mess.
1. About brown-bruised apples: Oxygen combining with acid does not make anything brown. Apples have some iron-containing proteins in them which react with oxygen in the apple and turn brown; it’s really rust. When apples have a cut surface, this reaction can be stopped by an acid, such as lemon juice. Odd to think of this, since lemon juice alone would cause elemental iron to rust, but the iron is part of a protein here and it needs the enzymes in the apple to help it take up the oxygen.
2. Rot in food usually refers to the action of bacteria or molds. Rancidity is a particular kind of food damage. It is the spoiling of oils, due to – yes – a reaction with oxygen.
3. I’m trying to think whether there is any source of energy in all the universe other than oxidation. Nuclear fission and fusion, of course… Anyway, the burning of an ordinary fire is one form of oxidation. An explosion is fast oxidation while the combustion in your car is a controlled explosion. Metabolism is a carefully controlled form of oxidation, in which carbon compounds are changed to water and carbon dioxide with the release of energy. Most metabolism involves such complex materials and mixtures of material that it sounds odd to call them chemicals, though, of course, everything in the world is ultimately a chemical.
4. The last paragraph explaining oxidation is correct, but here Hakim is up against one of the great difficulties of science writing – which is that what is most correct may be least clear to the elementary reader. This paragraph cannot be clear to her audience – what it says can only be clear to someone who already knows it.
- Finally, in the actual caption for the picture in the box, she says “To the naked eye, a nail looks shiny.” Then she goes on to talk about how a nail looks when it’s rusty and under a microscope. Well, just to be clear about it: if a nail is very shiny to the naked eye, it will be shiny under a microscope also.
- She continues, saying that “during oxidation, seen under a high-power microscope (left) the surface is covered with a corrosive oxide layer known as rust.” There are three mistakes here:
- First, it is after oxidation that you see rust. There’s no point saying “during oxidation” as if it would become invisible once the oxidation was complete.
- Second, any cheap magnifying glass will show rust, as will the naked eye, though it’s much more dramatic under a stronger magnification.
- Third, the layer is corroded iron, not corrosive oxide. Rust is not corrosive, a word which refers to things likely to produce corrosion. Rust is a product of corrosion, not a cause. Acids which encourage rust are corrosive.
- Therefore, if a nail is even slightly rusty to the naked eye, the microscope will reveal the rusting with a lot more texture. Things which are seriously corroded, like the objects in her picture (which must be more than a nail) may be very pretty indeed under the ‘scope.
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We need to say a little about mass, primarily in response to the third margin note on this page in which we are told that mass and energy and interchangeable. Hmmm.
The mass of an object is closely related to its weight — the more mass there is, the more weight. But mass isn’t the same as weight for two reasons: first, because mass doesn’t change when you’re on the Moon: it’s the real muchness of a physical object and second…
Oooh. Wait a minute. This one is harder.
Think about jumping on your bathroom scales — bouncing on them, that is. Obviously they would show a greater weight. What you may not have thought about is that even if you average the down and the up parts of your jump, that average will still be greater than your weight. Bouncing disturbs the scales, and it’s always going to look like a gain in weight.
Well, here’s the odd fact: Part of the mass of things is their motion, not their muchness. Not their large motion, like jumping on a scale, but the infinitesimal motions within their atoms. It’s not a very large part, and it doesn’t affect anything you are dealing with in your daily life, so you can forget it until you start your physics degree, but it is a fact and it’s one that Einstein and everyone who did deep physics in the 20th century had to learn to consider.
Now, it happens that you can sometimes separate out the jumping from the muchness and make it go somewhere else. When you do this, we say that you have converted mass into energy because the thing that jumps less loses mass. But it is a mistake to say that mass and energy are interchangeable, just like that, as if protons could become light. Everyone says it, not just Hakim — almost everyone — but it’s not true. The muchness can’t be converted to energy, only the jumpiness. I learned this when I read a book called Questioning Einstein.
In any case, Hakim has not thought this all the way through. She gives the standard law of conservation of mass — that mass is never lost no matter how many times it changes form. She already got into this with the piece on the pelican flask; and for Lavoisier’s time, that was enough. But if mass (some mass) can be be converted to energy, as Einstein learned, then it is not conserved, is it? Only the total, the sum of mass-plus-energy is conserved. This is the correct way to teach this concept once you bring up Einstein. It’s not necessary to mention Einstein in a chapter about Lavoisier, but if you decide to mention later discoveries, this is the correct way.
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Here is a text box about various revolutions — the American Revolution, and the Industrial Revolution, and then, introducing the French Revolution, Hakim continues, “Meanwhile, in France, another freedom revolution was brewing.” Another “freedom revolution”? Although she does eventually say that this last revolution got “out of hand,” this is just inexcusable, lumping the American and French Revolutions. The French Revolution was about anarchy and hatred, and this was so from the start, not just after it “got out of hand.” No study of history can be useful if the American and French revolutions are casually compared.
Notice the Universe 