Minus two hundred and fifty degrees centigrade! A destination so full of dread and so difficult to attain that they almost despaired of getting there, although it was only 40 degrees centigrade lower than what could currently be reached. Dewar, Kamerlingh Onnes, and other researchers reminded colleagues and lay audiences in speeches and articles that in this territory below the temperature of liquid oxygen, each drop of 10 degrees centigrade was the equivalent of lowering a temperature in the more normal range of 100 degrees centigrade, and much harder to accomplish. There seemed no other way to get there but by expanding the cascade series.
In January 1884 von Wróblewski reported producing a liquide dynamique (constantly changing liquid) of hydrogen by cooling the gas with liquid oxygen, then allowing it to expand rapidly, which dissipated the energy and lowered the temperature; but the product was not a quietly boiling liquid in a test tube. Almost immediately, Olszewski reported the same result from his cascades: colorless drops running down the side of a tube. Later in 1884, Dewar told the readers of the Philosophical Magazine that Olszewski's work in progress meant that scientists would not have to wait much longer for "an accurate determination of the critical temperature and pressure of hydrogen." As things turned out, this was the last good thing James Dewar would ever have to say about Karol Olszewski.
In the meantime, another laboratory had entered the race, one under the command of Heike Kamerlingh Onnes at the University of Leiden in the Netherlands. Kamerlingh Onnes took up his duties as professor of physics and as chief of the research laboratory in November 1882, at the relatively young age of twenty-nine, and after beating out another serious contender for the position, Wilhelm Conrad Rontgen, who in 1901 would be awarded the first-ever Nobel Prize in physics, for his work on x-rays. Onnes was chosen in part because he was thoroughly Dutch, while Rontgen, although he had lived in Holland since the age of three and been educated at Dutch schools, had been born in Prussia.
Onnes grew up in a home that he later recalled as studious and isolated. His father was a roofing-tile manufacturer in Groningen, and because his parents felt themselves more refined and interested in culture than were the other burghers, yet not cultured enough to mingle with the university professors in the town, he recalled, they had few friends. "Therefore we remained at home, read much, talked about art, and developed ourselves consciously, so to say." In that home, a "deep inner culture" was combined with good manners and "neat and careful dress"; the Kamerlingh Onnes boys' entire mode of existence was "subservient to one central purpose: to become men." A younger brother became a well-regarded painter; another brother, a high government official. A French colleague would later recollect that Onnes would frequently stagger him by the "immensity of his erudition," particularly his knowledge of such matters as French literature.
In grade school, under the influence of the director, a professor of chemistry at Leiden, Heike developed an interest in science. At the university at Groningen, fellow students later recalled, Onnes would complete his schoolwork almost before they had begun their own, and he won first prize for a scientific essay comparing methods of obtaining the vapor density of gases. A fellowship took him to study with Bunsen and Gustav Kirchhoff; under their influence, he delved more into physics, becoming fascinated with Jean Foucault's pendulum, which led him to a doctoral thesis titled New Proofs for the Axial Changes of the Earth. It took him four more years to complete his studies, an interim he spent as a lecturer and laboratory assistant to one of the leading physicists of the Netherlands.
Onnes was so impressive when he defended his thesis in 1879 that the examiners dispensed with the usual custom of asking the candidate to leave the room while they decided his fate and instead, a senior chemist later recalled, "unanimously and without discussion" awarded him his doctorate. The preamble to his thesis, a quote from Helmholtz, became the touchstone of his life's work: "Only that man can experiment with success who has a wide knowledge of theory ... and only that man can theorize with success who has a great experience in practical work." Three years later, upon the retirement of an older professor of experimental physics at Leiden, Onnes ascended to that chair, and to the leadership of the university's experimental physics laboratory, the only such lab in the Netherlands. In his inaugural lecture, he expressed the wish that he could inscribe above every portal in his laboratory the motto Door meten tot weten, "Through measurement to knowledge." He also announced a program of quantitative research "in establishing the universal laws of nature and increasing our insight into the unity of natural phenomena." This was a direct reference to van der Waals's theory expressing the unity of gaseous, liquid, and solid states, known as the law of corresponding states, which, Onnes later wrote, "had a special charm for me." He set out to prove the theory through "the study of the divergences in substances of simple chemical structure with low-critical temperature." He deemed the theory so important that he later had plaster casts made of three-dimensional graphs of its equations.
During most of the rest of their lives, Onnes and van der Waals would meet monthly for private talks about the progress of the work. According to van der Waals, Onnes was "almost passionately driven to examine the merits of insights acquired on Dutch soil." Onnes echoed this estimate of his motivation, later writing that "the desirability of coming a step nearer to the secrets of absolute zero, and the fascination of the struggle against the unsubmissive [gases] in the country where van Marum first liquefied a gas are too strong, to allow the question to be forced away from one's thoughts."
At the outset of Onnes's operations, "only comparatively small means were at my disposal." The government of the Netherlands granted a modest subsidy to the lab, but Onnes could allocate just a portion of it to low-temperature research. Ethylene, an essential ingredient for lowering temperatures of other gases, was "very expensive" to purchase, and so he had to devote part of his lab space and time simply to making it. His lone assistant, who took care of the machinery, often had to abandon the construction of new equipment to repair older pieces, resulting in "intervals of stagnation which sometimes did much harm." Purchasing a Cailletet apparatus, Onnes replicated Cailletet's experiments, then those of Pictet, then those of the Poles, altering and improving the apparatus as he went along:
It took much time to free all pieces from smaller or greater leaks and defects, to lay perfectly tight packings, to make suitable conduits, to make cocks which do not get fixed by the cold ... to devise gauge-tubes showing the level of the condensed gas and filtering-apparatuses for protecting the cocks. Much that [later became] an article of trade was not yet known and had consequently to be made, which was very troublesome. And moreover there had to be acquired practice in all sorts of unusual work.
Three years into his research, with the Cailletet machine still not in perfect working order, and when he was still badly lagging behind Dewar and the Poles, Onnes did something no other competitor in this race would do. He began a monthly journal, Communications from the Physical Laboratory of the University of Leiden, issued in English, that was remarkable for its openness, its willingness to admit mistakes, and its sense of immediacy. Reading it, other researchers were instantly able to know all the important details of what Kamerlingh Onnes was doing, so they could readily replicate his experiments; this was in stark contrast to Dewar's articles and public demonstrations, which did not really reveal his methods and almost never reported his failures or what he had learned from them.
In 1885 von Wróblewski brought together the passion of his youth, electricity, and the low-temperature investigations of his maturity. Looking into the conductivity of copper wire, he found "extremely remarkable properties" at low temperatures, and in a paper he drew attention to the steady rise in the wire's ability to conduct electricity as the temperature was lowered by liquid nitrogen and other such fluids. It was an early first indication that in the far regions of the country of the cold, the conditions that characterized life at normal temperatures no longer applied.
In Mar
ch 1888 von Wróblewski was working late one night in his laboratory, alone, his fragile eyesight strained to the utmost by the effort to design a new apparatus with which to attempt the liquefaction of hydrogen. He knocked over a kerosene lamp. The glass shattered and poured onto him a stream of the flaming liquid; for the next three weeks he lingered in a hospital bed, then succumbed to his burns, dying at the age of forty-three.
The death of von Wróblewski was noted and mourned abroad, Estreicher writes, but had no effect on the work of Olszewski. The chemist had been attempting to perfect his own apparatus. Several times the glass tubing exploded, setting back his progress. In 1889 to 1890, he switched to metal containers. "This apparatus constituted the greatest progress in the field of the liquefaction of gases and was a real sensation in the scientific world of those days," Estreicher insisted, contending that Onnes and Dewar later adopted it—a claim that would be hotly disputed.
Dewar himself had only recently returned to low-temperature research after an explosion in his laboratory in 1886 that nearly killed him and that severely injured his associates. The accident was so bad that after 1890 in Great Britain, to prevent fatal mishaps that might come from mixing gases, valve threads on some combustible-gas cylinders were made right-hand, while those on the cylinders of other gases with which they might interact were made left-hand.
In 1892 Onnes and his associates finally perfected the equipment they had been working on for a decade, and for which they had even gone to the length of borrowing from the navy a pump formerly used to fill torpedoes with compressed air. Only then—years after Dewar and Olszewski were doing it routinely—were the Dutch able to produce liquid oxygen in useful quantities and to maintain it for their experiments. The apparatus promptly broke, spoiling everything. But not for long. Onnes appears to have used this crisis as the basis for successfully arguing with the elders of the university, and with the Dutch government, that he must have adequate funds and assistants to achieve any real progress. A year later, he pronounced himself proud of the new, large-scale liquefaction plant in his laboratory, which, he said, would enable him to begin a program of liquefying all the known gases and reaching down to the neighborhood of—250°C.
Approaching Christmas 1887, the managers of the Royal Institution told the aged John Tyndall that Dewar, rather than he, would give that year's annual Christmas lecture to children; Tyndall resigned, and the managers appointed Dewar director of the Royal Institution; it was rumored that Dewar insisted the Tyndalls vacate the director's flat by January 1.
A balding, middle-aged man in trim beard, starched collar, and formal black suit, Dewar did magic tricks with liquid oxygen boiling in a tube for the adult Friday Nighters. He extracted a drop of the liquid oxygen and put it on his arm, supposedly to "show that it was in the spheroidal condition," but really to demonstrate that he was not afraid of the cold tiger. He added alcohol to the liquid in the test tube, and the alcohol instantly froze into a solid within the liquid oxygen. He held a lighted taper over the test tube, and the vapor given off by the liquid ignited the taper into flaring flames. Having startled his audience, he then waxed philosophic, telling the men in evening jackets and the ladies in ball gowns that as science neared the projected temperature of liquefied hydrogen, the world would learn how those temperatures grandly altered many properties of matter. He prophesied that at or below the temperature of liquid hydrogen, "molecular motion would probably cease, and what might be called the death of matter would ensue."
He could make these predictions with some confidence because he had seen indications of astounding transformations from a lengthy and detailed series of experiments he conducted with J. A. Fleming, beginning in the late 1880s and lasting for many years thereafter. Fleming and his assistants made the measurements, while Dewar directed what was to be done and interpreted the results. These experiments accomplished more than any others in delineating many of the contours of the map of Frigor. It was an almost unworldly landscape they painted, one whose features had been etched by the fantastic transformative power of seriously low temperatures.
Scientists had long since established that a bit of chilling made it possible for metals to become better electrical conductors—it lowered the metals' resistance—but Fleming was unprepared for what happened when iron coils were plunged into liquid air: after, the coils registered one-tenth of the "resistivity" they had at room temperature. Dewar and Fleming found that as temperatures dropped drastically, so did resistance. At room temperature, the resistance of iron was 1, and that of copper was much better, at 5.9; but at—197°C, iron was at 8.2 and copper dropped to a breathtaking 34.6. This research moved Dewar to dream that at the absolute zero point, if it could ever be attained, "all pure metals would be perfect conductors of electricity....A current of electricity started in a pure metallic circuit would develop no heat, and therefore undergo no dissipa tion." * Fleming went so far as to propose a new definition for absolute zero: "the temperature at which perfectly pure metals cease to have any electrical resistance."
As Dewar widened his research, he reached out to other collaborators, including Pierre Curie, with whom he studied the effects of extreme cold on the emanations of radium and on the gases occluded by radium.
At extremely low temperatures, thermometers made of mercury or other liquids were freezing solid. Siemens in Germany had constructed a thermometer based on the curve describing the decline in resistance in a platinum wire, a curve that could by extrapolation give readings for the temperatures of other materials as they became ever colder. Dewar and Fleming began to use such "resistance" thermometers.
The ability to measure low temperatures did not help Dewar and Fleming make sense of the finding that a bath in liquid air made dramatic changes in the insulating capacity of substances that were already good insulators at room temperature. Glass, paraffin, and natural substances such as gutta-percha (a variety of natural rubber) and ebonite (an even harder rubber) did not lose insulating capacity but rather became even better insulators after being immersed in liquid air. The experimenters had no explanation for that. Nor could they come up with reasons for what happened to magnetization under the influence of liquid air or liquid oxygen. Dewar and Fleming were intrigued to find that while most magnets gained strength when subjected to intense cold, some did not; moreover, when pure iron was immersed in liquid oxygen, it afterward required a much greater magnetic field to magnetize it than was needed under normal conditions. Even mercury at very low temperatures could act as a magnet, whereas at room temperature it exhibited virtually no magnetic pull. To help explain that, the experimenters reminded themselves that in the periodic table, mercury was listed as a metal.
In the grip of Frigor, iron, copper, and zinc exhibited enhanced rigidity and greater strength: a coil that at room temperature could support only a pound or two of weight could support three times as much after immersion in liquid oxygen. When balls of various metals taken from the bath were dropped on an anvil, they bounced higher than they normally did, leading the researchers to conclude that lowered temperature produced greater elasticity in metals, and to guess that this might be traceable to increased molecular density of the supercooled metals.
It was a good guess, and its likelihood was spectacularly bolstered by the work of Dewar and Fleming on chemical affinities at the temperature of liquid oxygen. Generations of science students had been startled and delighted by demonstrations involving the violent reactions of some chemicals when brought into the presence of oxygen at room temperature, watching as these substances instantly formed oxides, a process that generated a great deal of chemical heat, sometimes accompanied by sparks and burnings. But when such usually volatile substances as phosphorus, sodium, and potassium were plunged into liquid oxygen, nothing happened. The ability of chemicals to combine, the researchers discovered, was all but abolished in the extreme cold. Not only that, but compounds that at room temperature would always generate electricity failed to do so at the temperature of liquid oxyge
n.
The most curious and unexpected of the experimental findings had to do with the optical properties of materials. Under the extreme cold, substances such as mercuric oxide, normally bright scarlet, faded to light orange, while white-colored substances intensified their whiteness, and blue-colored substances did not change their color at all. Reaching for explanations, Dewar and Fleming thought the changes in color corresponded to changes in the substances' specific absorption of light, but they could not be certain. Rounding a corner of the optical-properties valley, the researchers discovered the presence of something they recognized but had not suspected of existing in these latitudes: phosphorescence. All sorts of materials that in the normal-temperature world did not even give off the faintest of shines began to glow with their own bluish-colored light in the extreme cold—substances such as gelatin, paraffin, celluloid, rubber, ivory, and bone. Sulfuric and hydrochloric acids gleamed brightly. An egg immersed in liquid oxygen and then stimulated by an electric lamp radiated as a globe of blue light. Feathers glowed, too, as did cotton, wool, tortoiseshell, leather, linen, even sponges. Perhaps the ability to become phosphorescent had to do with the internal oxygen content of the material, but the experimenters couldn't prove that either. As with geographical explorers encountering strange flora and fauna in a country never before traversed, Dewar and Fleming, in their forays in the temperature region of liquid oxygen, simply captured the beasts, collected the flowers, and carried the samples back home to await further testing and eventual explanation.
Absolute Zero and the Conquest of Cold Page 15
