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The New Chemistry - Crash Course History of Science #18
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00:00:05.299 --> 00:00:09.250 One of the problems with the whole idea of a single Scientific Revolution is that some 00:00:09.250 --> 00:00:12.530 disciplines decided not to join any revolution. 00:00:12.530 --> 00:00:15.219 And others just took a long time to get there. 00:00:15.219 --> 00:00:19.400 In the case of chemistry—the study of what stuff is—a real scientific revolution, like 00:00:19.400 --> 00:00:23.169 in the Thomas Kuhn sense, didn’t really get going until the 1770s. 00:00:23.169 --> 00:00:27.919 Until then, mainstream chemistry in Europe was based on phlogiston theory, which may 00:00:27.919 --> 00:00:32.099 be difficult to wrap your head around because it is the opposite of how we understand chemical 00:00:32.099 --> 00:00:33.099 reactions today. 00:00:33.099 --> 00:00:38.280 To shake loose that particular scientific status quo, it took the power of the Enlightenment, 00:00:38.280 --> 00:00:42.520 and one of its most emblematic natural philosophers, Lavoisier. 00:00:42.520 --> 00:00:50.760 [Intro Music Plays] 00:00:50.840 --> 00:00:56.039 If the 1600s was the century of science in Europe, centered on London, then the 1700s 00:00:56.039 --> 00:00:58.859 was the century of philosophy, centered on Paris. 00:00:58.859 --> 00:01:03.100 This new philosophy largely consisted of a movement called the Enlightenment—dated 00:01:03.100 --> 00:01:08.170 by some from 1715, when France’s powerful “Sun King,” Louis the Fourteenth, died, 00:01:08.170 --> 00:01:10.970 to 1789, when the French Revolution started. 00:01:10.970 --> 00:01:16.220 The Enlightenment was a shift in ideas about knowledge, away from traditional sources of 00:01:16.220 --> 00:01:20.870 authority, like the Church, and toward the kind of scientific rationality described by 00:01:20.870 --> 00:01:21.870 Bacon. 00:01:21.870 --> 00:01:26.360 This aspect of the Enlightenment is summed up by the catchphrase sapere aude, or “dare 00:01:26.360 --> 00:01:27.360 to know.” 00:01:27.360 --> 00:01:32.210 This suggested that knowing is something you should do—a moral good. 00:01:32.210 --> 00:01:33.850 This was an “Age of Reason.” 00:01:33.850 --> 00:01:38.840 The Enlightenment was also about social values, such as individual liberty, the progress of 00:01:38.840 --> 00:01:43.530 civilization, and religious tolerance, including the separation of church and state. 00:01:43.530 --> 00:01:49.130 The Enlightenment at times even fed into anti-religious, specifically anti-Catholic, feelings, setting 00:01:49.130 --> 00:01:52.730 the stage for a later perceived break between science and religion. 00:01:52.730 --> 00:01:57.160 The term “Enlightenment” was coined by German writer Johann Wolfgang von Goethe, 00:01:57.160 --> 00:02:00.200 and it was used by Voltaire, and later by Kant. 00:02:00.200 --> 00:02:04.670 Thinkers like them—called les philosophes, or “the philosophers”—met in scientific 00:02:04.670 --> 00:02:07.660 societies, literary salons, and coffeehouses. 00:02:07.660 --> 00:02:12.560 The philosophes saw it as their job to discover the laws of nature—the natural law that 00:02:12.560 --> 00:02:14.900 helped guide human behavior. 00:02:14.900 --> 00:02:19.480 They dreamed of a “republic of letters,” a world ruled by rational thought and guided 00:02:19.480 --> 00:02:20.800 by reasoned debate. 00:02:20.800 --> 00:02:26.230 So, yes, if you remember episode two: the philosophes were kinda like the Presocratics. 00:02:26.230 --> 00:02:30.990 The ideas of the Enlightenment undermined the authority of kings and churches and helped 00:02:30.990 --> 00:02:35.800 set the intellectual stage for the soon-to-come revolutions in the United States, France, 00:02:35.800 --> 00:02:36.800 and Haiti. 00:02:36.800 --> 00:02:41.450 But the Enlightenment was also about increasingly centralized state power and colonization of 00:02:41.450 --> 00:02:44.610 non-Europeans, which we talked about two episodes ago. 00:02:44.610 --> 00:02:49.140 Statistics, for example, was developed at this time to serve the interests of nation-states 00:02:49.140 --> 00:02:50.780 and early corporations. 00:02:50.780 --> 00:02:53.390 So we can also call this the Age of Empire… 00:02:53.390 --> 00:02:58.870 Perhaps no object better represents the Enlightenment than the ambitious book named the Encyclopédie. 00:02:58.870 --> 00:03:06.950 Edited by Jean d’Alembert and Denis Diderot from 1751 to 1777, the twenty-two volume Encyclopédie 00:03:06.950 --> 00:03:12.360 attempted to organize literally all of the knowledge available to humanity. 00:03:12.360 --> 00:03:13.360 Basically... 00:03:13.360 --> 00:03:14.360 Wikipedia! 00:03:14.360 --> 00:03:19.940 The Encyclopédie physically demonstrated three big ideas: First, knowledge is cumulative. 00:03:19.940 --> 00:03:23.800 Humans add new knowledge to our collective pool all the time. 00:03:23.800 --> 00:03:25.970 Second, knowledge is recordable. 00:03:25.970 --> 00:03:28.970 We can transmit knowledge through things like books. 00:03:28.970 --> 00:03:31.370 And third, knowledge is political. 00:03:31.370 --> 00:03:36.870 Diderot, like Bacon, believed that knowledge should be used to alleviate human misery. 00:03:36.870 --> 00:03:42.230 Diderot hoped to “change the general way of thinking” by popularizing recent achievements 00:03:42.230 --> 00:03:45.500 in science and technology and combating superstition. 00:03:45.500 --> 00:03:47.990 He wanted to use knowledge to help people out. 00:03:47.990 --> 00:03:53.090 He also thought that all traditional beliefs should be reexamined “without sparing anyone’s 00:03:53.090 --> 00:03:54.180 sensibilities.” 00:03:54.180 --> 00:03:58.510 But strict censorship by the state made any explicitly anti-religious articles impossible, 00:03:58.510 --> 00:04:02.260 so Diderot had to cleverly slip in critiques of the church. 00:04:02.260 --> 00:04:07.380 For example, in the cross-reference for the entry on the Eucharist: “see cannibalism.” 00:04:07.380 --> 00:04:13.230 Now, the Encyclopédie systemized knowledge in a neat way, but it was largely qualitative, 00:04:13.230 --> 00:04:17.650 describing things according to values—for example, what a good ship looks like. 00:04:17.650 --> 00:04:22.379 But Enlightenment thinkers increasingly dreamed of quantification, or describing things in 00:04:22.379 --> 00:04:25.779 numbers—like units of length, mass, heat, and so on. 00:04:25.779 --> 00:04:30.400 But for quantification to work, you have to have an agreement about how to measure things. 00:04:30.400 --> 00:04:32.830 In other words, you have to have standards. 00:04:32.830 --> 00:04:38.939 The meter, for example, was defined by a commission of scientists in France in the 1790s as one 00:04:38.940 --> 00:04:42.479 ten-millionth of the earth’s meridian through 00:04:42.480 --> 00:04:46.440 The commission included Pierre-Simon Laplace, who wrote the five-volume 00:04:46.442 --> 00:04:49.700 Celestial Mechanics, starting in 1799. 00:04:49.710 --> 00:04:54.909 This greatly expanded Newton’s work on classical mechanics, opening up a range of topics to 00:04:54.909 --> 00:04:56.949 the problem-solving power of calculus. 00:04:56.949 --> 00:05:00.659 Celestial Mechanics became a sort of Principia - volume two. 00:05:00.659 --> 00:05:05.129 And in order to actually measure the meter, the commission sent out two guys, Pierre Méchain 00:05:05.129 --> 00:05:07.920 and Jean-Baptiste Delambre, to make measurements. 00:05:09.380 --> 00:05:10.460 ...I'm not good at French. 00:05:10.480 --> 00:05:12.020 This was a time of widespread war in Europe. 00:05:12.029 --> 00:05:16.009 Méchain and Delambre struggled against skirmishes, yellow fever, and imprisonment—but they 00:05:16.009 --> 00:05:17.080 got the job done. 00:05:17.080 --> 00:05:21.889 And along with standards, measurement required new instruments, like the barometer and electrometer, 00:05:21.889 --> 00:05:26.620 as well as new ways of interpreting data, AKA statistics, which were also pioneered 00:05:26.620 --> 00:05:27.620 by Laplace. 00:05:27.620 --> 00:05:31.759 By the end of the eighteenth century, physics was already well on its way to rationalization, 00:05:31.759 --> 00:05:34.069 quantification, and even standard measurement. 00:05:34.069 --> 00:05:35.659 But what about chemistry? 00:05:35.659 --> 00:05:40.219 In the late 1700s, natural philosophers believed that chemical reactions occurred thanks to 00:05:40.219 --> 00:05:46.479 an ether—a colorless, odorless, “self-repulsive,” extremely fine, and therefore hard-to-measure 00:05:46.479 --> 00:05:48.569 fluid—called phlogiston. 00:05:48.569 --> 00:05:52.440 According to phlogiston theory, this ether was released during combustion. 00:05:52.440 --> 00:05:56.099 For example, a burning candle was thought to release phlogiston. 00:05:56.099 --> 00:06:00.379 If you covered that candle with a jar, the flame would go out, because the air would 00:06:00.379 --> 00:06:04.270 become saturated with phlogiston and couldn’t absorb any more. 00:06:04.270 --> 00:06:08.930 This is exactly the opposite of how we now understand it: that the flame goes out because 00:06:08.930 --> 00:06:13.069 it’s used up all of the oxygen, which is necessary for a chemical reaction. 00:06:13.069 --> 00:06:17.150 Likewise, it was thought at the time that, when plants grew, they absorbed phlogiston 00:06:17.150 --> 00:06:18.380 from the air. 00:06:18.380 --> 00:06:22.570 When their wood was burned, it released phlogiston back into the air. 00:06:22.570 --> 00:06:27.080 Or when we ate them, our bodies released phlogiston through respiration and body heat. 00:06:27.080 --> 00:06:31.379 In this system, “phlogisticated air” or “fixed air” was what we would now call 00:06:31.379 --> 00:06:33.099 carbon dioxide. 00:06:33.099 --> 00:06:35.939 Joseph Black isolated fixed air in 1756. 00:06:35.939 --> 00:06:39.449 “Dephlogisticated air,” on the other hand, was oxygen. 00:06:39.449 --> 00:06:43.599 This system worked pretty well to explain chemical reactions qualitatively—why they 00:06:43.599 --> 00:06:48.320 seemed to appear a certain way—but no one could quantify phlogiston. 00:06:48.320 --> 00:06:51.379 And minor anomalies in phlogiston theory kept adding up. 00:06:51.379 --> 00:06:56.689 For example, mercury gained weight during combustion, even though, by releasing phlogiston, 00:06:56.689 --> 00:06:57.879 it should have lost weight. 00:06:57.879 --> 00:07:03.569 The person who changed chemistry from a qualitative discipline to a quantitative one was Antoine-Laurent 00:07:03.569 --> 00:07:04.569 de Lavoisier. 00:07:04.569 --> 00:07:08.729 A good example of an Enlightenment natural philosopher, Lavoisier was born to a noble 00:07:08.729 --> 00:07:11.279 family in Paris in 1743. 00:07:11.279 --> 00:07:15.349 He studied law but was obsessed with geology and chemistry. 00:07:15.349 --> 00:07:17.660 Lavoisier also worked on the metric system. 00:07:17.660 --> 00:07:21.780 Lavoisier first presented research on chemistry, in a paper about gypsum, to the French 00:07:21.780 --> 00:07:24.080 Academy of Sciences in 1764. 00:07:24.080 --> 00:07:27.900 In 1768, the Academy made Lavoisier a provisional member. 00:07:27.909 --> 00:07:32.909 Two decades later, he would become the founder of the “new chemistry,” revolutionizing 00:07:32.909 --> 00:07:34.439 the entire discipline. 00:07:34.439 --> 00:07:39.289 ThoughtBubble, show us what this means: Lavoisier knew phlogiston theory well. 00:07:39.289 --> 00:07:41.039 But he began his chemical research with 00:07:41.040 --> 00:07:47.200 the hypothesis that, during combustion, something is taken out of air rather than put into it. 00:07:47.200 --> 00:07:52.020 That hypothesis turned out to be correct, and that something turned out to be oxygen. 00:07:52.029 --> 00:07:57.659 Lavoisier’s tested his hypothesis by accounting for inputs and outputs in chemical reactions—a 00:07:57.659 --> 00:08:01.939 perfect example of the eighteenth-century quantification of science. 00:08:01.939 --> 00:08:07.699 And Lavoisier also discovered that the mass of matter remains the same even when it changes 00:08:07.699 --> 00:08:09.099 form or shape. 00:08:09.099 --> 00:08:10.830 Which is very important! 00:08:10.830 --> 00:08:15.490 Working carefully over years, he generated the first modern list of elements. 00:08:15.490 --> 00:08:21.460 He named oxygen in 1778, hydrogen in 1783, and silicon—merely a prediction at that 00:08:21.460 --> 00:08:23.039 point—in 1787. 00:08:23.039 --> 00:08:27.520 In fact, Lavoisier and his allies developed a whole new nomenclature for chemistry, in 00:08:27.520 --> 00:08:28.520 1787. 00:08:28.520 --> 00:08:30.649 “Inflammable air” became hydrogen. 00:08:30.649 --> 00:08:33.460 “Sugar of Saturn” became lead acetate. 00:08:33.460 --> 00:08:37.969 “Vitriol of Venus”—which had also been called blue vitriol, bluestone, and Roman 00:08:37.969 --> 00:08:40.240 vitriol—became copper sulfate. 00:08:40.240 --> 00:08:43.320 Yeah, the new naming system was less fun than the old one. 00:08:43.320 --> 00:08:47.100 But it was more rational: the terms better described the underlying 00:08:47.100 --> 00:08:48.840 stuff they pointed to. 00:08:48.840 --> 00:08:52.360 “Copper sulfate” meant a compound of sulfur and copper. 00:08:52.360 --> 00:08:57.690 Lavoisier published the textbook Elementary Treatise of Chemistry in 1789, which taught 00:08:57.690 --> 00:08:59.519 only the new chemistry. 00:08:59.519 --> 00:09:03.670 In the introduction to his book, Lavoisier also separated heat and chemical composition. 00:09:03.670 --> 00:09:07.920 So water is water whether it’s heated up to steam or cooled down to ice. 00:09:07.920 --> 00:09:12.640 He understood that heating something up doesn’t always change what it is, fundamentally. 00:09:12.640 --> 00:09:17.910 To explain these state changes, Lavoisier made up a new ether, which he called the 00:09:17.910 --> 00:09:18.910 caloric. 00:09:18.910 --> 00:09:23.610 Caloric could penetrate a block of ice, melting it into water by pushing the ice particles apart. 00:09:23.610 --> 00:09:24.980 Thanks Thought Bubble. 00:09:24.980 --> 00:09:28.470 Spoiler: caloric is not thought to be a real thing today. 00:09:28.470 --> 00:09:31.839 (Many people wish calories weren’t real, but, here we are.) 00:09:31.839 --> 00:09:35.870 Led by the prominent English chemist Joseph Priestley, these old-timers kept modifying 00:09:35.870 --> 00:09:40.220 phlogiston theory so that it could rationally account for chemical reactions without falling 00:09:40.220 --> 00:09:44.550 apart, due to the whole phlogiston-in versus oxygen-out thing. 00:09:44.550 --> 00:09:49.230 Well into the 1780s, many chemists still believed in phlogiston—which no one had 00:09:49.230 --> 00:09:52.800 actually seen or measured—simply because it was familiar. 00:09:52.800 --> 00:09:53.800 What changed their minds? 00:09:53.800 --> 00:09:57.790 Well, Lavoisier and his allies published results that favored their system. 00:09:57.790 --> 00:10:02.470 But more importantly, the students who learned from them could only speak the language 00:10:02.470 --> 00:10:03.810 of the new chemistry. 00:10:03.810 --> 00:10:06.279 The phlogiston believers were increasingly isolated. 00:10:06.279 --> 00:10:11.680 Thus in a couple of decades, phlogiston moved from the center of chemistry into exile. 00:10:11.680 --> 00:10:16.220 With the new chemistry, Lavoisier brought the discipline into the system of rational, 00:10:16.220 --> 00:10:21.240 experimental science dreamed up by methodologists such as Bacon and fleshed out by Newton. 00:10:21.240 --> 00:10:25.360 Outside of chemistry, Lavoisier was a noble with a powerful state job: he worked at the 00:10:25.360 --> 00:10:29.720 hated tax collection agency of the French kingdom, known for being both secretive and 00:10:29.720 --> 00:10:30.720 violent. 00:10:30.720 --> 00:10:33.160 He profited from his job there, helping fund his chemical research. 00:10:33.160 --> 00:10:38.170 But the French Revolution broke out in 1789, and being an aristocratic tax collector was 00:10:38.170 --> 00:10:39.579 not a good look. 00:10:39.579 --> 00:10:42.480 Lavoisier was tried for defrauding the people of France. 00:10:42.480 --> 00:10:47.540 And the judge denied the appeal to save his life, despite his immense contributions to 00:10:47.540 --> 00:10:52.740 knowledge, declaring that: “The Republic needs neither scientists nor chemists; the 00:10:52.740 --> 00:10:55.060 course of justice can not be delayed.” 00:10:55.060 --> 00:10:57.620 Lavoisier died by guillotine in 1794. 00:10:57.620 --> 00:11:03.120 His friend, mathematician Joseph-Louis Lagrange, said of Lavoisier’s death: “It took them 00:11:03.120 --> 00:11:09.129 only an instant to cut off his head, but France may not produce another such head in a century.” 00:11:09.129 --> 00:11:13.760 Now, how was Lavoisier so successful at setting up the new chemistry as a paradigm? 00:11:13.760 --> 00:11:15.940 Well, he had a lot of support! 00:11:15.940 --> 00:11:20.790 Marie-Anne Pierrette Paulze, AKA “Madame Lavoisier,” was born into a noble family 00:11:20.790 --> 00:11:23.410 in south-central France in 1858. 00:11:23.410 --> 00:11:26.660 And she contributed significantly to Antoine’s work. 00:11:26.660 --> 00:11:31.120 She translated his texts into English, and after Antoine’s death, she published his 00:11:31.120 --> 00:11:34.310 complete papers, securing his legacy in the field. 00:11:34.310 --> 00:11:39.509 Madame Lavoisier eventually remarried another scientist, Count Rumford, a physicist who had a role in shaping 00:11:39.509 --> 00:11:40.779 thermodynamics. 00:11:40.779 --> 00:11:44.580 But she insisted on keeping Lavoisier’s name to show her allegiance to the man she 00:11:44.580 --> 00:11:45.480 loved. 00:11:45.480 --> 00:11:48.320 Also, Madame Rumford is way less cool. 00:11:48.320 --> 00:11:52.759 After the Lavoisiers, a new generation of thinkers continued to develop their ideas, 00:11:52.759 --> 00:11:54.100 in France and beyond. 00:11:54.100 --> 00:11:58.910 Notably, John Dalton observed that the ratio of elements in reactions were often made up 00:11:58.910 --> 00:12:05.000 of small numbers, meaning that chemical elements are in fact discrete particles, not fluids. 00:12:05.000 --> 00:12:09.490 He called these particles chemical atoms—true indivisible units. 00:12:09.490 --> 00:12:14.800 And Joseph Fourier published the Analytical Theory of Heat in 1822, using calculus to 00:12:14.800 --> 00:12:16.600 describe how heat flows. 00:12:16.600 --> 00:12:21.350 Fourier also discovered the greenhouse effect, or the capture of the sun’s radiation in 00:12:21.350 --> 00:12:22.350 the earth’s atmosphere. 00:12:22.350 --> 00:12:26.420 Next time—we’ll classify plants’ sexy parts, disintegrate a willow tree, and debate 00:12:26.420 --> 00:12:30.069 whether whole species can … go extinct. 00:12:30.080 --> 00:12:32.680 Join us for biology before Darwin! 00:12:32.680 --> 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