Episode 2.6.1: Supplemental-John Dalton and the Renaissance of the Atom

Hello, and welcome to The Scientific Odyssey. The Scientific Odyssey is a many-part journey into the history and philosophy of science. My name is Chad Davies, and I'm the writer, host, and producer of the podcast where we consider the ideas, processes, and results of over 2,500 years of scientific inquiry and discovery. Series 2, A History of the Atom. Episode 6.1, Supplemental. John Dalton and the Renaissance of the Atom. His last scientific measurement was made on July 26, 1844. In it, he recorded the temperature and the barometric pressure in a weak, scrawling hand, and then wrote, Little Rain. Sometime that night, he slipped his mortal coil and joined those whose greatness is enshrined in their contributions to human knowledge. His work in atmospheric measurement was enormous, consisting of over 200,000 separate observations from around England and on the European continent, from places as diverse as the inner city of London to the higher hills of the Lake District. But as titanic an endeavor as this was, he almost never missed a day and often made many observations on a single day if the condition warranted it. It paled in comparison to how he changed the way the world looked at that. The man was John Dalton, and he returned the idea of atoms to the center of the discussion of the nature of matter. Unlike many others, however, he was not a philosopher dabbling in metaphysical conjectures. He was something different, emerging from the field of natural philosophy and well on the way to being what we now think of as a scientist. But how did he get to his conclusion? Why was it he who insisted on bringing back the ideas of Democritus and Epicurus, and how did his idea differ from theirs and the atom of Boscovitch whom we discussed back in episode 2.4? In this supplemental, I hope to answer those questions as well as discuss a few other things about the scientific life of a man so different from the chemists of Europe. Dalton was born in early September of 1766 in a small village in Cumberland, England called Eaglesfield. His family was one of meager means as his father was a loom weaver of wools and linens for local sale. The Daltons were Quakers, another group of dissenters from the Church of England. Unlike Priestly, however, John Dalton would never rail against the exclusion from much of the English public square his life long membership in the Society of Friends would lead to. He was the youngest of three surviving children and was often the case for the working poor of the time he was expected to contribute to the family's means at a fairly early age. Due to his keen intellect and early grasp of many of the concepts taught in the basic school curriculum, he became a school teacher in his local school at age 12. Up until this time, his education in mathematics and sciences had been overseen both by his father and a gifted teacher by the name of John Fletcher who stressed rationality and approach. After becoming a young teacher himself, John was most influenced by a prominent fellow Quaker, Elihu Robinson, who was an instrument maker and a meteorologist, and it was Robinson who continued Dalton's instruction in both mathematics and natural sciences. At age 15, Dalton moved to a larger town called Kendall, 45 miles from his home, to join his older brother in operating a school there. This is a bit remarkable as it was usually the case of a person at that time, especially if they were poor, that they would rarely travel more than 20 miles from their place of birth any time during their lifetime. So for Dalton, 45 miles must have seemed a whole world away. While in Kendall, in addition to running the school, Dalton made the acquaintance of John Gough, a man of significant scientific attainment, as described by Dalton's biographer, John Price Milton. Gough had been blind since the age of two, but had overcome this impairment to rise into the British scientific community. He took Dalton under his wing and taught him the disciplined approach to work that would mark the rest of Dalton's career. In his 1793 work, Meteorological Observations and Essays, Dalton would write, To one person, more particularly, I am peculiarly indebted, not only in this respect, but in many others. Indeed, if there be anything new and of importance to science contained in this work, it is owing, in great part, to my having had the advantage of his instruction and example in philosophical investigations. Dalton would teach at Kendall from 1781 until 1793, when he would move to Manchester. Around 1790, Dalton had wondered if he should attempt to become a barrister or physician, but had been convinced that his low standing in English society would prevent him from doing so. As the lesser professions of being an attorney or an apothecary held little interest to him, Dalton decided to remain a teacher. It was also during his time at Kendall that Dalton began making the meteorological observations that would occupy much of the rest of his life. The first recorded measurements were made on March 24, 1787, most likely using instruments of his own construction. While his first attempts at instrument making were crude and error prone, he rapidly gained proficiency in the art of making thermometers, barometers, and even hygrometers for measuring humidity. His move to Manchester was undertaken upon his appointment to the New College there. The New College was a dissenting academy or college, institution of higher education, that had been created to give an educational path to Quakers who were barred from attending the great institution of England on religious grounds. Goe, who felt that Dalton's level of knowledge and expertise recommended him to the post, had arranged the appointment. Dalton would teach there for seven years before resigning his position in 1800. The reasons for this resignation have been debated, but it likely stemmed from financial difficulties at the institution and Dalton's recognition that he just wasn't a gifted lecturer. After this time, until his death, his income was obtained through private tutoring done at two shillings a lesson. Before moving on to his scientific works, there are a few points I'd like to make here. The first of these is that we see that Dalton's education was a product of working under the tutelage of several other men. While not a formal path through a structured educational system, the idea of Dalton working with and learning from others can clearly be seen. As I've mentioned previously, science is generally not something one does alone. The second point here is that while one might bristle at Dalton's exclusion from the educational system of England, such as it was at the time, on the basis of his religion, it was likely actually a benefit in this case. Like Priestley, Dalton would have received a much stronger foundation in the natural sciences in dissenting institutions than he would have at places like Oxford and Cambridge or the types of institutions and boarding schools that fed students to the bigger universities. These places still strongly emphasized a classical curriculum grounded in scholasticism, and thus it is very possible that Dalton would not have been exposed to the anti-phlogiston hypothesis of Lavoisier and the work in pneumatic chemistry being done both in England and France had he attended those kinds of schools. Finally, it is during this time that we see the character of Dalton as a person and a scientist emerge. He was a supremely rational person who weighed each decision and idea carefully. He lived a structured life in accordance with the dictates of his faith, which stressed humility and simplicity in all things. It would be, however, a mistake to think of Dalton as some sort of scientific robot. By all accounts, he was an engaging person who enjoyed the pastimes of the day, including bowling and a pint at the local pub. While he remained a lifelong bachelor in order to pursue his scientific work, he did enjoy female companionship, even if only in friendship. He was not the sort of misanthrope that Cavendish had been, nor was he a misogynist like Newton. He might be seen as the paradigm of the English bachelor gentleman whose profession and pursuit of knowledge left little room for marriage and family. So now that we know a little bit about the man, let's take a look at his scientific work. Upon moving to Manchester, one of the first things that happened was that Dalton was elected to the Manchester Literary and Philosophical Society. This was his first membership in a group specifically devoted to the sharing of knowledge and research and his selection was based, in part, on his publication of that first scholarly work we discussed, Meteorological Observations and Essays. While mostly ignored by the scientific community of Great Britain at the time, the work contained conclusions drawn from Dalton's first six years of observations of the weather and state of the atmosphere. In it, he would rediscover the idea of an atmospheric circulation cell first discussed by George Hadler. Additionally, one can find the seeds of a number of his later ideas, a topic to which we will return shortly. After his election to the Manchester Lit and Fill, as it was called, Dalton presented a remarkable paper for its time. The paper was on colorblindness, a condition both he and his brother suffered from, specifically the red-green variety. In the paper, he attributed the condition to a defect in the fluid filling the eyeball, which was a hypothesis that was disproven during his lifetime. He also showed the condition was, in fact, hereditary. This was the first time anyone had written about this particular medical condition and it gained wide enough notoriety that colorblindness for many years was known as Daltonism. Over the next several years, between about 1794 and 1800, Dalton presented additional works on all sorts of topics, ranging from gas pressure to heat conduction, from the nature of light to the Aurora Borealis, and in doing so, he established a reputation as a first-rate scientist. During this period, he continued to make meteorological observations, notably expanding the dataset to include higher elevation data due to his frequent travel to the Lake Region of England for vacation. One additional note to be made here is that with his election to the lit and fill, Dalton gained access to good laboratory facilities wherein he could perform experiments regarding a number of the topics we're going to discuss, most importantly though, the behavior of gases. In 1800, as I mentioned before, Dalton resigns his position at New College, a move that limited his income but afforded him significantly more time and flexibility to do the research he was interested in. In that same year, he was made Secretary of the Lit and Fill, a post that he would hold until 1817 when he was elected the body's president. It was during this period, between 1801 and 1808, that Dalton would do the work for which he is best known and to which we turn now. In the historical community, it was long held that Dalton's work leading to his atomic theory grew out of his participation in the research of pneumatic chemistry, specifically in determining laws for the relationship between the temperature, pressure, and volume of various gases. While this may be somewhat true, especially as his initial research progressed, what seems clear in the light of more recent research into his journals is that his interest in these systems grew directly out of his research with the atmosphere and the measurements he was taking for that research. These measurements suggested certain unaddressed problems that Dalton then investigated in a laboratory setting, which led him in turn to try to come up with an explanation for a number of different phenomena. As I mentioned briefly in the previous podcast episode, Dalton understood that the atmosphere was a mixture of different gases, mostly nitrogen and oxygen, but other things as well. What he didn't understand was why the heavier gas of carbon dioxide didn't just sink to the bottom of the atmosphere and kill everything, at least everything but the plants. This led him to begin to try and understand gas behavior, specifically with mixtures. His research here led him first to confirm the Gase-Lussac law, which in England at the time was known as Charles Law, which said that gases combine in ratios that can be expressed in whole numbers based on their volume. He then added to this his own observations that showed that the total pressure in a mixed gas is the sum of the partial pressures of each of the individual gases. This showed him that the gases had to be completely mixed together with each gas exerting its own pressure on the walls of a confining container. What Dalton wondered was how this could be the case, let's see if I can explain why this is a problem. At the time it was thought that gases, like fluids and solids, were continuous matter, but if gases were continuous matter, say like fluids, then they shouldn't be able to pass through each other. But what if they weren't continuous fluids? It was at this point that Dalton turned to a tool he likely developed as a teacher. He began working with pictorial models of gases. To represent a mixed gas, he first drew pictures of the individual gases and then laid them on top of each other, you can kind of think of it as stream flows of water or something like that. Now if the gases were like fluids, and he laid them down one on top of the other, they wouldn't work in the way his experiments had shown, they would always be getting in the way of each other and couldn't flow through each other. But, if they were made of particles, then the whole picture started to make a lot more sense. It turns out that Dalton had been reading a good bit of ancient literature and it is said that he had recently come across the ideas of atoms in both Hindu and Greek writings. What if, he wondered, gases were made of tiny particles? So what he did is he drew his pictures of gases, but instead of, you know, making them look like fluids or continuous matters, he made them, this time, look like tiny particles spread out inside of the container. He then laid the picture of each gas one on top of the other, and what he saw was a completely different picture. He saw that the particles of different gases could move through the spaces between the particles of the other gases. It was in that moment that Dalton became convinced of the atomic nature of matter. However, being convinced by some pictures sketched in one's spare time isn't science, and Dalton kind of knew that. He knew that what he needed was more than just part of an idea. So he began working to determine the differences in the weights of different types of atoms, what we would call atomic weight today. In this work, Dalton was guided by a certain picture of the atom that he had developed from what Newton had speculated about them. This group of statements about how matter is made up is now known as Dalton's Atomic Theory, and at its heart is a model of what the atom is. So let's break that down. First, the theory part. All matter is comprised of a small number of elements. An element is a material made up exclusively of one type of atom, and its properties are dependent on the properties of that type of atom. All other matter is mixtures or compounds of different elements, meaning that they are combinations of different types of atoms. In chemical reactions, atoms combine, disassociate, and or recombine to form new compounds or substances. The second part of this, the model part, is the thing that talks about the atoms themselves. Historically, this model is often times called the billiard ball model of the atom, and here's how it goes. The model says atoms are extremely small, hard, indivisible spheres. Each element is made of one type of atom, and one type of atom only. Atoms of different elements have different weights, and they combine in simple whole number ratios with other elements to form compound substances. In this description of the atom, we see some similarities to the atoms of Democritus and Epicurus, but what is more notable are the differences. For Dalton, these are not some sort of metaphysical construct of which there are an infinite number in both quantity and variation. These are real, definitely hard things. They almost seem childish when compared to the lofty ideas of the Greek and Hindu writers you might have been reading, but they were superior to those things because they explained what was being seen in a very concrete fashion. I think one has to wonder if the years of teaching children, whose need for concrete tools with which to work, shaped Dalton's approach here. In fact, one of the things that we know is that in order to teach atomic theory to others, Dalton had a number of small 1-inch wooden spheres made to show how atoms would work on a more macroscopic scale. In relation to this approach, historian W.V. Ferrer writes, John Dalton had a pictorial imagination. There was never anything shadowy or metaphysical about his atoms. They were, in Newton's phrase which he often quoted, solid, massy, and hard. Too small to see, but very real. This concreteness of imagination proved to be Dalton's great strength as a chemist. For it so happened that chemistry thrived in the 19th century when it was naive and pictorial and it languished when it tried to be subtle and abstract. It was with this model that in the years between about 1803 and 1810, Dalton began to explain the results he and other chemists were getting in their researches. The first was the obvious explanation of Richter's and Proust's Law of Definite Proportions. The atomic theory made this result seem almost trivial. Of course elements always combined in specific proportions. If matter were made of atoms, they'd have to. The same would be true for the Gay-Lussac Law, at least in the part of it that said that gases combined in integer ratios of their volume. But what really sealed the whole thing for many was Dalton's new Law of Multiple Proportions. He showed that if two elements combined in multiple way, say in the case of carbon monoxide and carbon dioxide, the weights of the changing element, in this case oxygen which is just one oxygen atom in carbon monoxide versus two oxygen atoms in carbon dioxide, the change would happen in integer multiples of each other. This could only happen if the oxygen came in those discrete units, if it came in specific numbers of atoms. In his researches, Dalton was able to confirm this relationship with a number of other substance and it was strong empirical evidence of his idea against those who would question it in the years to follow. Now Dalton consolidated his ideas in a book titled, A New System of Chemical Philosophy, published in 1808, that had an appendix that was added in about 1810. The reception of these ideas was initially pretty mixed, especially in England. The first problem was that while Dalton did supply experimental confirmation of his ideas, the work was often sloppy and a bit haphazard, especially when it came to those apparent or atomic weights. The reason for this is likely that once Dalton had seen the big picture, that overarching model, he felt he only needed rough confirmation. This was especially true in establishing the apparent weights of the elements. It was only once Brasilius had done his monumental work of analyzing over 2,000 different compounds to come up with the apparent weight of 50 or so elements, that many of the issues with Dalton's theory were resolved. The second problem was that in his theory, Dalton had used Occam's razor to predict how various things would combine. Now if you recall, Occam's razor says, take the simplest explanation one can take when possible. It should be noted that Occam's razor is a principle, not a requirement. One of the things that he had said, Dalton that is, is that when two elements combine in only one way, they would combine in the simplest binary ratio. Hence, since water was at the time, was the only compound of hydrogen and oxygen that was known, he assumed that it was made of one atom of each, rather than the form of two hydrogen atoms and one oxygen atom we know it to be now. And this would take some time to sort out, and finally when it was, it solved a lot of problems, but again, it was used as evidence against the model for a while by people opposed to it. Now finally, there was the much more intractable problem of the other result of the Gay-Lussac Law, which showed that the volumes of the reactant gases didn't always become the volume of product that Dalton's theory would have predicted. As I mentioned in the last podcast, the issue here was that Dalton and others had assumed gases were strictly atomic in nature, i.e. that hydrogen gas was comprised or consisted of only hydrogen atoms, not hydrogen molecules like we know it to be now. While Avogadro would solve this problem almost immediately, everybody missed his solution until almost 50 years later after Dalton's death. However, acceptance of the atomic theory happened fairly quickly after the initial problems were resolved for most chemists, especially those chemists in France who immediately saw its applicability, its convenience, and its usability. The other issues of the theory were held by most chemists to be things to be figured out rather than as deal breakers, since the theory did so much to explain all of the other results and measurements that were being obtained. By about 1865, only a few chemists remained who actually disagreed with the theory. As additional physical evidence was added first from the fields of thermodynamics and statistical mechanics, and then from electromagnetism, it became the foundational idea in all fields of research. Like so many others who make paradigm-altering contributions to science, the remainder of Dalton's scientific career would be pretty pedestrian in most ways. This was likely due to his need to continue to promote, explain, and teach the atomic theory. Dalton would be elected to the Royal Society in 1822, but he felt that body was of little value by that time. In 1831, in part owing to his role as president of the Lytton Phil, he helped found the British Association for the Advancement of Science. In 1833, he was elected as one of the eight foreign members of the French Academy of Sciences. In 1837, Dalton suffered a small stroke, and then a more significant one a year later that left him with a speech impediment. In May of 1844, he suffered a third significant stroke, and on July 27th of that year, he passed away. His legacies were many, not the least of which were his many atmospheric observations. It is said by many historians of chemistry that Dalton was the Kepler of chemistry, and that he put forward a model that while he didn't understand its causes or mechanisms, was absolutely essential for his field to make progress. Though those explanations would not become available until the 20th century, it is clear that his atomic model created the framework in which all subsequent thinking would be done. Dalton's atom was a chemical one, and it explained only the chemical phenomena of its day, and the evidence supporting it was restricted almost completely to gas pressures and chemical reactions. However, with his evidence, it was once again thought to be useful to explain other physical phenomena using his atoms, as we'll examine in a later podcast episode. Beyond this, however, was the importance of his concrete approach to explanation. His reliance on modeling would become a hallmark of British science, both in chemistry and in physics. Faraday, Maxwell, Thomson, and Rutherford would all benefit following Dalton's example as would both Bohr and de Broglie in Europe, though these last two would mark the transition to a more highly mathematical and theoretical model building process to explain the atomic and subatomic phenomena they encountered. As we close, it should be noted that Dalton's atom stands in contrast to that of Boscovich, whose work in 1763 was well regarded by philosophers, especially in Europe. Boscovich, if you'll recall, favored a monad point atom that created forces that mediated interactions between matter. Dalton's atom is an altogether different thing. Dalton didn't know what created the combinations, though he did think that like atoms repelled each other, while atoms of different elements attracted. To move forward, we'll have to spend a couple of episodes investigating two very different areas of research to see what can be determined about those two pictures. The first area will be that of electricity, while the second will be centered around the questions of heat and energy, an area where one of Dalton's students from Manchester, James Prescott Jewell, will have a great deal to say. Before we do that, however, it will be useful for us to take a digression into attempts to organize all the information that was becoming available to chemists by the middle of the 19th century. We'll do that next in an episode titled, The Periodic Atom. So until next time, full sails on your journey.