So much for transmutation. But many people, Lavoisier included, still believed water was a basic element. Lavoisier ended that illusion when he invented an apparatus with a double nozzle. He would shoot a different gas through each nozzle, hoping they would combine and form a third substance. One day he decided to work with oxygen and hydrogen, expecting them to mix together into some kind of acid. What he got was water. He described it as "pure as distilled water." Why not? He was making it from scratch. Obviously, water was not an element but a substance that could be manufactured from two parts hydrogen, one part oxygen.
In 1783 a historical event occurred that would indirectly further chemistry. The Montgolfier brothers demonstrated the first manned air flights with hot-air balloons. Soon thereafter J. A. C. Charles, a physics teacher no less, rose to a height of 10,000 feet in a balloon filled with hydrogen. Lavoisier was impressed; he saw in such balloons the possibility of rising above the clouds to study meteors. Soon thereafter he was named to a committee to explore methods of cheaply producing gas for the balloons. Lavoisier set up a large-scale operation to produce hydrogen by decomposing water into its constituent parts by percolating it through a gun barrel filled with hot iron rings.
At this point, no one with any sense still believed that water was an element. But there was a bigger surprise for Lavoisier. He was splitting apart water now in vast quantities, and the numbers always came out the same. Water yielded oxygen and hydrogen in a weight ratio of eight to one every time. Clearly, some sort of neat mechanism was at work here, a mechanism that might be explained by an argument based on atoms.
Lavoisier did not speculate much about atomism, except to say that simple indivisible particles are at work in chemistry and we don't know much about them. Of course, he never had the opportunity to sit back in retirement and write his memoirs, in which he might have elaborated further on atoms. An early supporter of the Revolution, Lavoisier fell out of favor during the Reign of Terror and was sent to the guillotine in 1794 at the age of fifty.
The day after Lavoisier's execution, the geometer Joseph Louis Lagrange summed up the tragedy: "It took them only an instant to cut off that head, and a hundred years may not produce another like it."
BACK TO THE ATOM
The implications of Lavoisier's work were investigated a generation later by a modest, middle-class English schoolteacher named John Daiton (1766–1844). In Dalton we have at last our made-for-TV-movie image of a scientist. He appears to have led a totally uneventful private life and never married, saying that "my head is too full of triangles, chemical processes, and electrical experiments, etcetera, to think much of marriage." A big day for him was a walking tour and maybe attendance at a Quaker meeting.
Dalton started out as a humble teacher in a boarding school, where he filled his spare hours reading the works of Newton and Boyle. He put in over a decade at this job before landing a position as a professor of mathematics at a college in Manchester. When he arrived he was informed that he would also have to teach chemistry. He complained about twenty-one hours of teaching per week! In 1800 he resigned to open his own teaching academy, which gave him the time to pursue his chemical research. Until he unveiled his atomic theory of matter shortly after the turn of the century (between 1803 and 1808), Dalton was still considered little more than an amateur in the scientific community. As far as we know, Dalton was the first to formally resurrect Democritus's term atom to mean the tiny indivisible particles that make up matter. There was a difference, however. Recall that Democritus said atoms of different substances had different shapes. In Dalton's scheme, weight played the crucial role.
Dalton's atomic theory was his most important contribution. Whether it was "in the air" (it was) or whether history gives far too much credit to Dalton (as some historians say), no one questions the tremendous influence of the atomic theory on chemistry, a discipline that soon became one of the most pervasively influential sciences. That the first experimental "proof" of the reality of atoms came from chemistry is also most appropriate. Remember the ancient Greek passion: to see an unchanging "arche" in a world in which change is everywhere. The a-tom resolved the crisis. By rearranging a-toms, one can create all the change one wants, but the rock of our existence, the a-tom, is immutable. In chemistry, a relatively small number of atoms provide enormous choice because of the possible combinations: the carbon atom with one oxygen atom or two, hydrogen with oxygen, or chlorine or sulfur and so on. Yet the atoms of hydrogen are always hydrogen—identical one to another, immutable. But here we go, forgetting our hero Dalton.
Dalton, noting that the properties of gases can best be explained by postulating atoms, applied this idea to chemical reactions. He noticed that a chemical compound always contains the same weights of its constituent elements. For example, carbon and oxygen combine to form carbon monoxide (CO). To make CO, one always needs 12 grams of carbon and 16 grams of oxygen, or 12 pounds of carbon and 16 pounds of oxygen. Whatever units you use, the ratio is always 12 to 16. What can the explanation be? If one atom of carbon weighs 12 units and one atom of oxygen weighs 16 units, then the macroscopic weights of carbon and oxygen that disappear into CO will have this same ratio. This alone would be a weak argument for atoms. However; when you make hydrogen-oxygen compounds and hydrogen-carbon compounds, the relative weights of hydrogen, carbon, and oxygen are always 1 to 12 to 16. One begins to run out of alternative explanations. When the same logic is applied to many dozen compounds, atoms become the only sensible conclusion.
Dalton revolutionized science by declaring that the atom is the basic unit of the chemical element and that each chemical atom has its own weight. Here he is, writing in 1808:
There are three distinctions in the kinds of bodies, or three states, which have more specially claimed the attention of philosophical chemists; namely, those which are marked by the terms elastic fluids, liquids, and solids. A very famous instance is exhibited to us in water, of a body, which, in certain circumstances, is capable of assuming all three states. In steam we recognize a perfectly elastic fluid, in water a perfect liquid, and in ice a complete solid. These observations have tacitly led to the conclusion which seems universally adopted, that all bodies of sensible magnitude, whether liquid or solid, are constituted of a vast number of extremely small particles, or atoms of matter bound together by a force of attraction, which is more or less powerful according to circumstances....
Chemical analysis and synthesis go no farther than to organize the separation of particles one from another and their reunion. No new creation or destruction of matter is within the reach of chemical agency. We might as well attempt to introduce a new planet into the solar system, or to annihilate one already in existence, as to create or destroy a particle of hydrogen. All the changes we can produce consist in separating particles that are in a state of cohesion or combination, and joining those that were previously at a distance.
The contrast between Lavoisier and Dalton in scientific styles is interesting. Lavoisier was a meticulous measurer. He insisted on precision, and this paid off in a dramatic restructuring of chemical methodology. Dalton had many things wrong. He used 7 instead of 8 for the relative weight of oxygen to hydrogen. He had the composition of water and ammonia wrong. Nevertheless, he made one of the profound scientific discoveries of the age: after some 2,200 years of speculation and vague hypothesis, Dalton established the reality of atoms. He presented a new view which, "if established, as I doubt not it will in time, will produce the most important changes in the system of chemistry and reduce the whole to a science of great simplicity." His apparatus was not a powerful microscope, not a particle accelerator but some test tubes, a chemical balance, the chemical literature of his day, and creative inspiration.
What Dalton called an atom was certainly not the a-tom that Democritus envisioned. We now know that an oxygen atom, for example, is not indivisible. It has a complex substructure. But the name stuck: what we commonly call an atom today is Dalton's atom. It's a chemical atom, a s
ingle unit of a chemical element, such as hydrogen, oxygen, carbon, or uranium.
***
Headline in the Royal Enquirer in 1815:
CHEMIST FINDS ULTIMATE PARTICLE, ABANDONS BOA CONSTRICTORS, URINE
Once in a blue moon a scientist comes along who makes an observation that is so simple and elegant that it just has to be right, an observation that appears to solve, in one swift stroke, a problem that has tormented science for thousands of years. Once in a hundred blue moons the scientist is actually right.
All you can say about William Prout is that he came very close. Prout put forward one of the great "almost correct" guesses of his century. His guess was rejected for the wrong reasons and by the fickle finger of fate. Around 1815 this English chemist thought he had found the particle from which all matter was made. It was the hydrogen atom.
To be fair, it was a profound, elegant idea, albeit "slightly" wrong. Prout was doing what a good scientist does: looking for simplicity, in the Greek tradition. He was looking for a common denominator among the twenty-five known chemical elements at the time. Frankly, Prout was a bit out of his field. To his contemporaries, his main accomplishment was writing the definitive textbook on urine. He also conducted extensive experiments with boa constrictor excrement. How this led him to atomism, I don't care to speculate.
Prout knew that hydrogen, with an atomic weight of 1, was the lightest of all the known elements. Maybe, said Prout, hydrogen is the "primary matter" and all the other elements are simply combinations of hydrogens. In the spirit of the ancients, he named this quintessence "protyle." His idea made a lot of sense, because the atomic weights of most of the elements were close to integers, multiples of the weight of hydrogen. The reason for this was that relative weights were then typically inaccurate. As the precision of atomic weights improved, the Prout hypothesis was crushed (for the wrong reason). Chlorine, for example, was found to have a relative weight of 35.5. That blew away Prout's concept because you can't have half an atom. We now know that natural chlorine is a mixture of two varieties, or isotopes. One has 35 "hydrogens" and the other has 37 "hydrogens." These "hydrogens" are really neutrons and protons, which have almost the same mass.
What Prout had really hypothesized was the existence of the nucleon (either of the particles, the proton or the neutron, that make up the nucleus) as the building block of atoms. It was a hell of a good try by Prout. The drive for a system simpler than the set of twenty-five or so elements was destined to succeed.
Not in the nineteenth century, however.
PLAYING CARDS WITH THE ELEMENTS
We end our breakneck jaunt through two hundred-plus years of chemistry with Dmitri Mendeleev (1834–1907), the Siberian-born chemist responsible for the periodic table of the elements. The table was an enormous step forward in classification and at the same time constituted progress in the search for Democritus's atom.
Even so, Mendeleev took a lot of guff in his lifetime. This odd man—he seems to have survived on a diet based on sour milk (he was testing some medical fad)—was subjected by his colleagues to considerable derision for his table. He was also a great supporter of his students at the University of St. Petersburg, and when he stood behind them during a protest late in his career the administration booted him out.
Without students, he might never have constructed the periodic table. When first appointed to the chair of chemistry in 1867, Mendeleev couldn't find an acceptable text for his classes, so he began writing his own. Mendeleev saw chemistry as "the science of mass"—there's that concern with mass again—and in his textbook he came up with the simple idea of arranging the known elements by the order of their atomic weights.
He did so by playing cards. He wrote the symbols of the elements with their atomic weights and various properties (for example, sodium: active metal; argon: inert gas) each on a separate note card. Mendeleev enjoyed playing patience, a kind of solitaire. So he played patience with the elements, arranging the cards so that the elements were in order of increasing atomic weights. He then discovered a certain periodicity. Similar chemical properties reappeared in elements spaced eight cards apart; for example, lithium, sodium, and potassium are all chemically active metals, and their positions are 3, 11, and 19. Similarly, hydrogen (1), fluorine (9), and chlorine (17) are active gases. He rearranged the cards so that there were eight vertical columns, with the elements in each column having similar properties.
Mendeleev did something else that was unorthodox. He felt no compulsion to fill in all the slots in his grid of boxes. Just as in solitaire, he knew that some of the cards were hidden in the deck. He wanted the table to make sense not only reading across the rows but also reading down the columns. If a space called for an element with particular properties and no such element existed, he left it blank rather than trying to force an existing element into the slot. Mendeleev even named the blanks, using the prefix "eka," which is Sanskrit for "one." For example, eka-aluminum and eka-silicon were the gaps in the vertical columns beneath aluminum and silicon, respectively.
The gaps in the table were one of the reasons Mendeleev was so widely mocked. Yet five years later, in 1875, gallium was discovered and turned out to be eka-aluminum, with all the properties predicted by the periodic table. In 1886 germanium was discovered, which turned out to be eka-silicon. The game of chemical solitaire turned out to be not so nutty.
One of the factors that made Mendeleev's table possible was that chemists had become more accurate in measuring the atomic weights of the elements. Mendeleev himself had corrected the atomic weights of several elements, which did not win him many friends among those important scientists whose figures were being revised.
No one understood why the regularities appeared in the periodic table until the discovery in the following century of the nucleus and the quantum atom. In fact, the initial impact of the periodic table was to discourage scientists. There were fifty or more substances called "elements," basic ingredients of the universe that presumably could not be subdivided further—this meant more than fifty different "atoms," and the number was soon to swell to over ninety. This is a long way from an ultimate building block. Looking at the periodic table in the late 1800s should have made scientists tear their hair out. Where's the simple unity we've been seeking for over two millennia? Yet the order that Mendeleev found in this chaos pointed to a deeper simplicity. In retrospect, the organization and regularities of the periodic table cried out for an atom with some structure that repeated itself periodically. Chemists, however, were not ready to abandon the notion that their chemical atoms—hydrogen, oxygen, and so on—were indivisible. A more fruitful attack would come from a different angle.
Don't blame Mendeleev for the complexity of the periodic table, though. He was simply organizing the confusion as best he could, doing what good scientists do—looking for order in the midst of the complexity. He never was fully appreciated by his peers during his lifetime, never won the Nobel Prize, even though he was alive for several years after the founding of the Prize. At his death in 1907, however; he received the ultimate honor for a teacher. A band of students followed his funeral procession, carrying high above them the periodic table. His legacy is the famous chart of the elements that hangs in every laboratory, every high school chemistry classroom in the world.
For the final stage in the oscillating development of classical physics we swing from the study of matter and particles back to the study of a force. In this case, electricity. In the nineteenth century, electricity was considered almost a science unto itself.
It was a mysterious force. And at first appearance, it didn't seem to occur naturally, except in the frightening form of lightning. So researchers had to do an "unnatural" thing to study electricity. They had to "manufacture" this phenomenon before they could analyze it. We have come to realize that electricity is everywhere; all matter is electrical in nature. Keep this in mind when we get to the modern era, when we discuss exotic particles "manufactured" in accelerators.
&nbs
p; Electricity was considered as exotic in the nineteenth century as quarks are today. Today electricity surrounds us, another example of how humans can alter their own environment.
There were many heroes of electricity and magnetism in this early period, many of whom left their names on various electrical units. They include Charles Augustin de Coulomb (the unit of charge), André Ampère (current), Georg Ohm (resistance), James Watt (electrical power), and James Joule (energy). Luigi Galvani gave us the galvanometer, a device for measuring currents, and Alessandro Volta gave us the volt (a unit of potential or electromotive force). Similarly C. F. Gauss, Hans Christian Oersted, and W. E. Weber all made their mark and left their names on electrical quantities calculated to generate fear and loathing in future students of electrical engineering. Only Benjamin Franklin failed to get his name on any electrical unit, despite his significant contributions. Poor Ben! Well, he has his stove and his portrait on those hundred-dollar bills. Franklin noted that there are two kinds of electricity. He could have called one Joe and the other Moe, but he chose instead plus (+) and minus (—). Franklin termed the amount of, say, negative electricity on an object "electric charge." He also introduced the concept of conservation of charge, that when electricity is transferred from one body to another, the total charge must add to zero. But the giants among all of these scientists were two Englishmen, Michael Faraday and James Clerk Maxwell.
The God Particle: If the Universe Is the Answer, What Is the Question? Page 15
