Absolute Zero and the Conquest of Cold (19 page)

The dimensions of cold had just become more frigid: from the—90°C of chlorine and methane, to the—140°C of ethylene, down to the—180°C of oxygen. The 90-degree drop from the liquid chlorine of Faraday to the liquid oxygen of Olszewski and von Wrôblewski was the equivalent of having lowered the temperature from that of boiling water to that of water so shivering cold that immersion in it would instantly kill a human being. Previously, liquefied oxygen and nitrogen had existed only as short-lived droplets from a mist; now workable quantities of both elements had been obtained.

The man who had received von Wrôblewski's telegram in Paris was one of his teachers, and he wrote back conveying personal congratulations from himself and Jean-Baptiste Dumas, the president of the Académie, and to convey the gossip that the Polish feat had occasioned much chagrin that the liquefaction had not been accomplished in Paris. Another effusive letter came to the Poles from Cailletet; von Wrôblewski treasured this letter, he said in his return missive to Cailletet, because "it proves a rare greatness of spirit. You express your delight in something that justifiably ought to be your success."

Thus began an era of intense experimentation in liquefaction and on the properties and uses of liquefied gases. Many experimenters would build on the results and techniques jointly developed by von Wróblewski and Olszewski, but not the pair themselves, at least not as a team. Within months of their joint accomplishment, Olszewski and von Wróblewski quarreled and terminated their collaboration. The cause of their split remains obscure to this day; Olszewski's later colleague Estreicher offered perhaps the most balanced and logical assessment of it: "The chief reason ... was that each of them possessed a strong personality and differed in temperament, which made relations between them difficult; each of them wanted to work in the same direction, but in a different way, and neither would make concessions and be subordinate to the other." During the next five years, Estreicher observed, both the chemist and the physicist continued to conduct more liquefaction experiments, separately and intensively, "as if each of them wished to surpass the other."

The Poles' achievement took the group of questing scientists beyond a mountain peak to a point on the other side, and there now opened up, below, a vista no one had ever before seen: a great valley full of unrecognizable vegetation, rock formations, rivers, and geysers; a valley that invited their descent and exploration but that also promised harsh travel and continual hazard, for at every step they took the temperature fell and the land became stranger and more unlike the warmer territories they had left behind.

To descend further, all the groups adopted the technique Pictet had pioneered and the Poles had improved: the cascade. It was like a series of waterfalls, one beneath the other, the first one gentle but feeding water faster into the next, which in turn fed it still faster into the third, whence it emerged in a boiling roar. In a liquefaction cascade, the temperature of a gas was first lowered by the removal of lighter molecules, by pressure and by cooling, until the gas became a liquid; then that liquefied gas was used to reduce the temperature of a second gas, liquefying it; afterward, the second liquefied gas was
used to liquefy a third. Cascades permitted experimenters a wild ride down the mountain, from the—no°C reached by Faraday with the Thilorier mixture, all the way to—210°C, the lowest point beyond liquid oxygen that had yet been reached. Off ahead of them, the explorers could see the next landmark goal, the "critical temperature" at which they should be able to liquefy hydrogen. From the calculations of van der Waals, it was expected to be about -250°C.

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 March 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.