Absolute Zero and the Conquest of Cold

by Tom Shachtman

  The ability to use a liquid's own coldness to make a portion of it colder—though at the cost of warming the rest—was something Dewar liked to demonstrate. But Tripler's understanding of what he called the "self-intensification" of cold was faulty, and pushed him to utter the equivalent of a claim of perpetual motion. While legitimate scientists might have continued to ignore Tripler and let him go on to produce liquefied gases without comment, they could not stand someone selling what was, in effect, the snake oil of perpetual motion. Scientific American, which had earlier reported Tripler's feat and the testing of his products by the University of Pennsylvania, now printed the comments of the president of the Stevens Institute of Technology, who pointed out that the second law of thermodynamics made three-for-one production impossible. In 1899, with the controversy still going on, Harvard's senior physicist commented that Tripler's use of one to make three "will succeed only when water is found to run up-hill." Linde, on a lecture tour of the United States, also debunked the claim.

  The stock of Tripler's firm collapsed and shares became worthless; shortly, investigators found that most of the $10 million had gone into the pockets of the promoters and not into Tripler's manufacturing process. In reaction to this debacle, American businesses refused to have anything to do with the commercial use of liquefied air for some years thereafter.

  In France, the early history of liquefied air almost went the same route, but it did not, because Georges Claude was a better scientist than Tripler. The son of an engineer who was also the assistant manager of an ice cream company, Claude had been involved with the cold all his life. After his university training, he became fascinated with liquefied gases in the early 1890s, when he worked as an electrical engineer and chief of a laboratory at Les Halles, Paris's marketplace. At that time, liquefied acetylene was used in welding torches. Claude envisioned replacing the acetylene with a torch of carbon burning in pure oxygen, which he believed would shortly be separated out of air; at that moment, when liquid oxygen had been produced mainly in basic research laboratories, this was a fairly farsighted idea for anyone not part of the small circle of low-temperature researchers.

  In 1895 Claude learned about Linde's separation machine. The existence of such a machine thrilled him, and he became certain he was destined to do nothing less than establish the entire industry for the manufacture of liquefied gases. To accomplish that, he would have to operate at the forefront of science, he wrote, which would require great intellectual energy and "brutal perseverance, the daughter of obstinacy and the sister of stubbornness and bad temper." Perseverance meant putting up his own money and convincing friends to loan him theirs, for a total of 50,000 francs, with which he formed a company, not to manufacture liquefied gases right away but first to test a variety of production equipment. As Claude later wrote in a memoir, he came to the key insight by questioning what Linde had done: "Why does he expand his air through a single tap? If this air was made to push a piston, it would produce more work and consequently more cold." He concluded that Linde had avoided the piston method because he was "afraid—quite rightly—that the normal lubricants would freeze [at the very low temperatures] and block his machine." Claude searched for a better lubricant. On the evening of May 25,1902, with the syndicate about to expire the next day, incurring the loss of all of the 50,000 francs, he made a final improvement to the lubricant and machine, and the whole process worked beautifully, using only 20 atmos pheres of pressure to make liquid air, rather than the 200 atmospheres of pressure used by Linde's apparatus.

  Claude's process was not merely an incremental technological advance, historian Ralph Scurlock contends; it was a "mechanical revolution so large as to constitute a second technological breakthrough" in the field that would soon become known as cryogenics. The magnitude of the breakthrough was obvious enough for Claude to form a new company within two months, with a capital of 100,000 francs, christened L'Air Liquide, Société Anonyme pour L'Etudie et L'Exploitation des Procédés Georges Claude.

  Its products, and those of the Linde and British Oxygen groups, were immediately in demand. Steel producers saw that the use of liquid oxygen could upgrade the old air-blast furnaces, helping them produce steel of greater purity and tensile strength, at lower cost. Liquid nitrogen's ability to provide nitrogen gas became essential to the production of calcium nitrate fertilizer, ammonia, and saltpeter—the latter product used for explosives, as Tripler had predicted.

  Within a short time of their establishment, the companies founded by Linde and Claude found that the appetite for their products was large, and continuing to grow. Along with artificial refrigeration and artificial manufacture of ice—industries that were also continuing to grow by leaps and bounds—the new liquefaction manufacturers made it likely that the twentieth century would be the first ever in the history of the world to be characterized by extensive commercial exploitation of the cold.

  10. The Fifth Step

  IN THE CHRONICLES OF many geographic explorations, there comes a moment when a far prize moves into clear view, and all pretense at examining the intervening landscape drops away, in favor of throwing every available resource into the thrust to reach the goal. In the exploration of the cold, that moment arrived when hydrogen was liquefied in quantity and the existence of helium on Earth had been revealed. On learning about the availability of liquid hydrogen, Kamerlingh Onnes later wrote, "I resolved to make reaching the end of the road my purpose immediately." The goal that became so tangible was the possible liquefaction of helium, which all the competitors in the race now believed could be made to happen at less than 10 degrees above absolute zero.

  In 1898 Dewar solidified hydrogen, using a combination of techniques, one of them based on the absorptive power of charcoal. He first evacuated hydrogen-gas molecules from a dewar of hydrogen and used charcoal to absorb them. That cooled the liquid to the point where it solidified. Then, by applying suction to solid hydrogen, Dewar reached down precisely as far as he had predicted, to within 13 degrees of absolute zero. "But there or thereabouts," he wrote, "our progress is barred."

  Preliminary analysis showed that helium resisted liquefaction even at—260°C. Because scientists had already descended hundreds of degrees from normal temperatures, the remaining 13 degrees might seem to a layman only a slight distance to travel. "But to win one degree low down the scale," Dewar wrote, "is quite a different matter from doing so at higher temperatures; in fact, to annihilate these few remaining degrees would be a far greater achievement than any so far accomplished in low-temperature research."

  In a presidential address to the BAAS, Dewar painted the liquefaction of helium as the next great goal of science, the last stop on the way to the Ultima Thule, absolute zero. He also predicted the characteristics of liquid helium: it would have a boiling point of about 5 K; it would be twice as dense as liquid hydrogen and seventeen times as dense as saturated helium vapor; it would have a negligible surface tension; and it would be difficult to see.

  Dewar was able to imagine the mysterious, pristine, frigid glory of liquid helium, but to liquefy it he required gaseous helium in quantity, and he didn't have enough. Supply also became of prime importance for Onnes, Olszewski, and others still in the race for the cold pole. In Great Britain, the largest concentration of helium had been found in the mineral springs at Bath. By a combination of circumstances and connections, Ramsay for a while controlled access to this source of helium, which was a problem for Dewar. But Dewar had the only apparatus that could provide the liquid hydrogen Ramsay needed to do further research on the inert gases. Several scientists, Dewar among them, had postulated the existence of another inert gas with a molecular weight between that of argon and helium, and Ramsay was working hard to find it. Ramsay and Dewar could have made a nice trade, helium-shale for liquid hydrogen, but their personalities wouldn't permit it, and they were at a standoff.

  In 1901 the impasse was broken when Morris Travers of Ramsay's laboratory successfully constructed a hydrogen liquefier;
in an article about it, Travers acknowledged help from Hampson, and he also pointed out that the apparatus had cost a mere £35, which his readers understood to be a slap at Dewar, whose apparatus had cost thousands of pounds, and who had fretted in public about the high cost of conducting low-temperature research. Actually, Travers had cannibalized or borrowed equipment whose value was the equivalent of thousands of pounds; liquefying hydrogen could not have been done at that time with available techniques and £35 worth of materials.

  During the next few years, using liquid hydrogen as their investigative tool, Ramsay, Rayleigh, and their group discovered xenon, neon, and krypton, completing the array of "rare" gases that would win the two major researchers Nobel Prizes in chemistry and physics in 1904. (Dewar chafed at that, among other reasons because neon was positioned on the periodic table precisely where he had predicted it would be.) In the midst of this research, Ramsay, Travers, and Hampson attended a party given by one of Dewar's friends, even though they did not want to, to prevent their rival from guessing by their absence that they were on the verge of a discovery. Ramsay legitimately feared that Dewar would find new rare gases before he did, based on Dewar's comments when Ramsay or Rayleigh would cautiously speak about their progress at scientific meetings. Travers would later charge that Dewar had not been an "imaginative" enough chemist to have found the rare gases. More likely, Dewar was too intent on liquefying helium just then to pay attention to any other goal. Dewar had a reciprocal, legitimate fear of the Ramsay-Travers group, because Travers's liquefier put them in contention in the race for absolute zero, along with Olszewski and Onnes, who soon produced liquefied hydrogen and aimed at liquefying helium.

  During the next several years, the lead in this race changed hands several times among these groups, with each edging closer, down to within 10 degrees of absolute zero. Later on, in 1906, Travers designed an apparatus to liquefy helium, but he subsequently lamented, "Just when all this was ready I had to leave for India, and the experiment was never carried out."

  Dewar sensed he had the most to fear from the laboratory at Leiden. Since Heike Kamerlingh Onnes had begun the experimental physics lab there in 1882, it had always been a step behind in the race, but Onnes had never permitted the distance between it and the leader of the moment to widen. A quarter of a century had passed, and although Onnes's hairline had receded to a thin fringe at the back of his pate, and his mustache had come to resemble that of a walrus, he had developed into a pillar of the scientific establishment, a man cherished for his strict regard for measurement, and for taking things one step at a time. Virtually alone among experimental physicists of his day, he had set out on a deliberate program of what would today be called "big science," the establishment of substantial laboratory sections and cadres devoted to thermodynamics, electricity, magnetics, and optics. "He ruled over the minds of his assistants as the wind urges on the clouds," recalled physicist Pieter Zeeman, who trained under Onnes. "He could achieve miracles with a flattering remark or witty (sometimes biting) irony. Even those who were above him on the hierarchical ladder fell for his charm ... and at the last moment a decision beneficial to Onnes could sometimes be achieved."

  While overseeing and developing the other sections of the laboratory, Onnes himself relentlessly pursued the liquefaction of gases. His ego did not keep him from adopting whatever innovation was made by another competitor, then improving it greatly—for instance, when he finally set up his own continuous-process hydrogen liquefier, it produced 4 liters per hour, a quantity vastly outstripping what Dewar, Olszewski, or Travers could make from their machinery.

  Similarly, Onnes had nurtured an additional strength: in 1901, adjacent to his laboratory building, he had begun the Society for the Promotion of the Training of Instrument-Makers, a workshop and school that supplemented the one he had previously established for machinists and electro-technicians, and he had set these men to work improving his facilities and machinery. Also, the low-temperature laboratory at Leiden was now beyond worries about cost; Onnes enjoyed the confidence of Queen Wilhelmina and the fullest of government support for his work. His equipment was so large and of such good quality, and his attendant assistants were so well trained, that physicists from all over the world vied to spend a sabbatical or a summer at Leiden. Even the young Albert Einstein applied for a position; he never received an answer to his letter to Onnes, and he went on to other pursuits. Later, the two men would develop a friendship.

  As Onnes aged, the tubercular weakness in his lungs, evident since childhood, was exacerbated—perhaps by the noxious gases of the laboratory—and he struggled to be well enough to work; his wife's assistance in maintaining his health was widely admired. Onnes lived in Ter Wetering, a beautiful home by the Old Rhine river with a lovely view, but for years was not well-to-do. As he would recall in a letter to van der Waals, he endured decades of poverty, "care-ridden years [with] appalling difficulties." The theorist comforted Onnes with the saw that "time sifts admirably well that which has real value from the other things," suggesting that vindication of the greatness of Onnes's work, as well as of van der Waals's own theories, would eventually arrive.

  Some in the Netherlands chided Onnes for being too patient, for taking too many measurements before thrusting ahead in liquefaction. He ignored the cavils, confident of eventual applause, and continued to build his organization, his apparatus, his communications, his network of supporters in other European laboratories, and his storehouse of knowledge.

  Dewar's recognition of Onnes's strengths may have been one reason he was always courteous to Onnes, even during the years he was savaging Olszewski and Ramsay. Dewar pleased Onnes by repeatedly referring to van der Waals as a genius underappreciated in countries beyond the Netherlands. For his part, Onnes went out of his way in his publications to pay tribute to Dewar's accomplishments.

  The two men were perhaps most alike in being autocratic, old-style masters of laboratories. Dewar refused to give much credit to his assistants, even though both Robert Lennox and James Heath each lost an eye during their long service with him, and he would not permit his assistants to become familiar, rebuking another associate who dared to call him "Sir James" after Dewar had been knighted. Similarly, in later years a top-hatted Onnes would drive with his horse and wagon to pay Sunday social calls on his technicians. During one such visit, an assistant asked for a raise; Onnes refused, saying "Haven't you just bought two nice bicycles?" When an idea occurred to Onnes at home, he would ring a bell on the side of his house, summoning his chief assistant Gerrit Flim, who lived on the opposite bank of the Old Rhine, and who would have to drop what he was doing and row across to discuss the idea with his boss. Although Onnes treated full colleagues with complete deference, there are stories that he was less respectful of doctoral or postdoctoral students and that he seldom shared credit with them on articles; he also required students to donate part of their stipends for the upkeep of the laboratory. One subsequently recalled their master's rules: they should work all day in the lab, taking notes in a little pocket notebook, and in the evening should write up their notes into a neat report. A student could have "a day off for love; I mean when you were engaged. But you could not get a day off really to listen to a theoretical lecture because [Onnes believed that] experimental physics requires the whole man." Other stories, however, paint Kamerlingh Onnes as the perfect colleague, generous of spirit, and the catalog of his publications shows that as he aged, he became progressively more willing to share credit for the work done under his direction.

  In 1902, the second year Nobel Prizes were given out, the physics award went to H. A. Lorentz, a friend and colleague at Leiden, and to Pieter Zeeman, for whom Onnes had served as thesis advisor; the award was for their discoveries regarding the theoretical basis for the splitting of the spectral lines of sodium in a magnetic field. Onnes had as yet made no achievements of similar import, though it was widely believed that he would soon do so. In honor of Zeeman and Lorentz, Onnes commissioned his nephew H
arm, a noted artist, to make a stained-glass window memorializing their work.

  Dewar and Onnes differed in one critically important area: Dewar's continual stream of published papers made very little use of others' theories—including that of van der Waals—and Dewar wrote no theoretical papers of his own. Onnes was continually guided by theory, and he spent much of his time making calculations from theory to predict isotherms that would reveal the critical temperatures of gases to be liquefied, then experimenting to verify the predictions. An exchange of letters in 1904 highlights this difference. When Onnes congratulated his rival on becoming Sir James, Dewar chided him for going overboard, because he, Dewar, was neither a baronet nor a knight, then went on to declare in the same emotional tone, "Exact physical measurements and pioneering work do not go well together. Such refined matters I must leave you to settle." To which Onnes replied, "The determination of the isotherms is the rational way to get data for calculating the critical points ... and exact determination of isotherms is just in my line of accurate measuring work."

  In preparation for his assault on absolute zero, Onnes pushed hard to determine the isotherms of hydrogen and helium. Later he would look back and view these efforts as the most crucial to his accomplishments, writing, "Before the determination of the isotherms had been performed I had held a perfectly and different opinion [of the possibility of liquefying helium] in consequence of the failure of Olszewski's and Dewar's attempts" to do so. After determining the isotherms, however, he became convinced he was on the right path.