Absolute Zero and the Conquest of Cold (22 page)

Meanwhile, Dewar pushed on by himself, employing Joule-Thomson expansion. He had used it years earlier to produce liquid air, but until 1895 he seemed not to have considered combining it with a "regenerative" process, one that would cool the air further each time it went through the apparatus. When his new apparatus was nearing completion, in early 1896, he described some experiments using it in an article that gave only a nod to Linde and contained a sneering footnote disparaging the mention of Hampson in a report by a French experimenter—even though, as historian Scurlock points out, Dewar's new apparatus owed a significant debt to Hampson's. Dewar also reported that his new machine could only reduce hydrogen gas to much lower temperatures than ever before, but he pledged to soon "overcome" the remaining technical "difficulties" and produce liquid hydrogen.

As Dewar neared his goal, his two main competitors, Olszewski and Onnes, each suffered a misstep. According to Tadeusz Estreicher, then employed by Hampson in London, Olszewski stumbled because his bid to buy a Hampson apparatus failed when the Jagiellonian University would not come up with the funds. Without a new method for lowering temperatures beyond that of liquid oxygen, Olszewski could not produce liquid hydrogen.

Onnes's problem came from a more unexpected source. In mid-1895 the town council of Leiden decided that the use of compressed gases in the low-temperature section of Onnes's laboratory could cause an explosion that would damage the entire building and the surrounding area—and therefore his laboratory ought to be shut and low-temperature research forbidden. Ninety years earlier, during the Napoleonic occupation of the Netherlands, an ammunition ship had exploded in a Leiden canal, destroying about five hundred buildings. The building in which Onnes's low-temperature laboratory was located had been erected on the ruins of the destroyed area
of town. "When the town council learned that the laboratory housed considerable quantities of compressed hydrogen, a wildly combustible gas, the historical memory of the ship's explosion drove them into a panic," writes Rudolf de Bruyn Ouboter, a twentieth-century director of the Leiden low-temperature laboratory. As a result of that panic, Onnes's low-temperature work at Leiden was suspended while a commission looked into the matter.

Mortified, Onnes wrote to Dewar in 1896 that he was unable to repeat and verify Dewar's latest "splendid" experiments "for a reason you will be astonished to hear," and he asked Dewar for a favor, pleading, "I do not think you go so far in secrecy that you will not assist a fellow worker." The favor was for Dewar to answer a series of questions about his laboratory in the middle of London, for the edification of the investigating Dutch commission. Dewar responded with good grace, even overstating the case for the relative safety of the equipment by telling Onnes that his own laboratory, where the dangerous gases were held, was directly underneath the auditorium of the Royal Institution; actually, it was two floors below. Dewar also managed not to mention to the commission the explosion in that laboratory that had nearly killed him in 1886. Similar questions that Onnes put to Olszewski were also answered in a reassuring manner.

The key fact presented to the commission was that the explosion of a cylinder of compressed gas would do less damage than the explosion of an amount of gunpowder that it was legal to own and transport. The case went all the way to the Supreme Court of the Netherlands, which decided Onnes could resume his work. By then several years had elapsed, and during the interim Dewar won the hydrogen lap of the race toward absolute zero.

On May 10,1898, after months of construction, testing, and preliminary trials, Dewar and his two assistants, Robert Lennox and James Heath, cranked up the jumble of pumps, cryostats, tubing, gas-intake valves, and liquid-collection points that filled the basement of the Royal Institution, making the space more resemble the boiler room of a factory than a scientific laboratory. The apparatus was a series of liquefaction machines. The first set, or step, produced chloromethane, which was used to cool the ethylene of the second step, which was itself then used to cool oxygen to the point of liquefaction. That liquid oxygen became the primary coolant for the attempt at liquefying hydrogen. After the hydrogen had spent many cycles in the regenerative process, Dewar and his associates succeeded in cooling the gas to—205°C. Then, while the gas was under a pressure of 180 atmospheres, they released the hydrogen suddenly and continuously into a vacuum vessel that was surrounded by a—200°C atmosphere and through that vacuum vessel into a second encased by a third. Within the space of five minutes, Dewar shortly reported, twenty cubic centimeters of liquid hydrogen were collected. The liquid was clear and colorless, with a readily observed meniscus (curved upper surface). After five minutes, however, "the hydrogen jet froze up, from the accumulation of air in the pipes frozen out from the impure hydrogen," and the experiment was forced to a stop.

Dewar was elated to have liquefied the last of the permanent gases. Wanting to prove to himself that this liquefied hydrogen was colder than any substance yet available, he plunged into the new liquid a tube filled with liquid oxygen; the oxygen froze to a bluish white solid, which could only happen if the temperature of the new liquid was lower than that of the oxygen. Dewar believed for a while that he had also managed to liquefy helium. He claimed that feat in a telegram to Onnes—"Liquefied hydrogen and helium"—but shortly he decided that the additional condensate was from traces of impurities in the hydrogen. Perhaps to discourage Kamerlingh Onnes from returning to the race, Dewar then accentuated the difficulties, writing to him in November 1898, "My troubles I can see are only beginning. It will be a long time before Hydrogen is
on tap.
"

Another problem: The platinum-resistance thermometer did not give completely trustworthy readings of the boiling point of hydrogen; upon reaching what Dewar believed to be that point, the plati
num thermometer seemed to stop working, and Dewar wondered if it had "arrived at a limiting resistance," below which the changes in resistance had become too small or too difficult to measure. Seeking some positive information from the thermometer's failure, he concluded—as he later wrote—that there was "no longer any reason to believe that at the absolute zero, platinum would become a perfect conductor of electricity," or by extension, that any other pure metal would do so. This contradicted the earlier prediction of his collaborator, Fleming, but Dewar did not try to prove his new contention, or to construct a theory to explain the apparent failure of the resistance thermometer.

Instead, Dewar used liquid hydrogen to accomplish what had previously been impossible. A year earlier, he had teamed with Henri Moissan, the discoverer of fluorine, to liquefy that gas. They could not do it at liquid-oxygen temperatures, but now, using liquid hydrogen, they were able to solidify fluorine. Liquid hydrogen also allowed them to determine that fluorine, unlike many other chemicals, remained reactive at very low temperatures: when they directly mixed solid fluorine and liquid hydrogen, the mixture violently exploded.

Since Dewar was still uncertain as to the precise temperature of liquid hydrogen, he searched for a thermometer to measure it and found one of an entirely new type, containing gaseous hydrogen under pressure. Using it, Dewar estimated the boiling point of hydrogen at 20 to 22 K, or—250°C. "With hydrogen as a cooling agent," he confidently predicted, "we shall get to from 13 to 15 of the zero of absolute temperature, and ... open up an entirely new field of scientific inquiry."

A few days after Dewar had made his preliminary communication about the liquefaction of hydrogen in quantity, William Hampson gave a lecture on the "self-intensive refrigeration of gases," which Dewar attended. Dewar challenged the upstart's claim that in addition to liquefying air and oxygen, he had liquefied hydrogen. Hampson reiterated his claim in the next issue of
Nature
and added that several years earlier, he had gone to the Royal Institution and briefed Dewar's assistant, Robert Lennox, about the machine he was perfecting; Hampson implied that Lennox had then told Dewar, and that Dewar used the information to construct his hydrogen-liquefaction apparatus. Dewar thundered in the following issue that he would have liquefied hydrogen in the same way at the same time even if Hampson had never been born. Three additional letter thrusts from Hampson and three more ripostes from Dewar followed, in subsequent issues. The conflicting claims were never resolved, and today one can only conclude that both men had right on their side: Dewar clearly had some knowledge of Hampson's work, perhaps from Hampson's patent application if not from his visit to Lennox; but equally, Dewar's search for a way to intensify the cold had led him to the same principles of Joule-Thomson expansion and the regenerative cycle that Hampson—and Linde—adopted. In later years, Dewar would go out of his way to avoid mention of Hampson in his occasional histories of low-temperature research, just as he also attempted to erase Olszewski's name from those histories. These unseemly overreactions appear to have been mandated by Dewar's obsession with his low-temperature goal and his egotism about the worth of his achievements.

A painting of Dewar lecturing, presumably on the hundredth anniversary of the Royal Institution in 1899, still hangs on the institution's walls today. The solemn stocky man, in his frock coat and pointed beard, is behind a table full of flasks, burners, and small apparatus, and underneath a screen that features projected images of the equipment. He holds a vacuum flask at arm's length before him, while Heath and Lennox behind him ready other materials for the demonstrations. Rapt attention is focused on Dewar by an elegantly attired audience composed of such distinguished visitors as Marconi, and the artistic, scientific, and political elites of the British Isles, including Kelvin, Stokes, Lord Rayleigh, and Rayleigh's brother-in-law, Prime Minister Arthur Balfour.

The lecture was about liquefying hydrogen, and in it Dewar
crowed that "Faraday's expressed faith in the potentialities of experimental inquiry in 1852 has been justified forty-six years afterwards by the production of liquid hydrogen in the very laboratory in which his epoch-making researches were executed." For this first public demonstration of liquid hydrogen, Dewar pulled out all the stops. He dipped a piece of metal in liquid hydrogen, then removed it; air instantly condensed around the metal, forming a solid coating that then melted to a liquid, which he collected in a cup. Into that cup he inserted a red-hot splinter of wood, which ignited as oxygen evaporated from the liquid air. Using the liquid hydrogen, he produced phosphorescence in all sorts of substances, decreased electrical resistivity in metals, sent ordinary thermometers shooting down until they failed, and by cooling oxygen into a liquid, turned it blue. He showed that liquid hydrogen was fourteen times less dense than water, and that it could magnetize cotton wool containing traces of liquid oxygen.

Dewar closed by expressing his gratitude to Robert Lennox in the most fulsome words he ever used publicly for an employee, avowing that "but for his engineering skill, manipulative ability and loyal perseverance, the present successful issue might have been indefinitely delayed," and by giving thanks to the members for supporting his work, coupled with a warning that future research in the extreme cold would be immensely difficult and very expensive.

The notable British scientists from the era of Bacon, Boyle, and Newton in the seventeenth century down through that of Davy, Faraday, and Kelvin in the nineteenth had for the most part disdained commercial endeavor as beneath the dignity and beyond the purview of the basic researcher. But the heyday of that notion had passed, along with the time when the lone scientist in his personal laboratory could make significant discoveries. Across the English Channel, Dewar's rival Kamerlingh Onnes was in the process of establishing the first "big science" endeavors in the low-temperature physics laboratory at Leiden, with its ancillary school for instrument makers and other assistants; Onnes was also moving in the direction of encouraging interchange between his laboratory and the research and development facilities of manufacturers who wished to exploit the commercial potential of the cold.

While James Dewar's battle with Hampson did indeed knock that particular amateur out of the scientific race toward absolute zero, Dewar accomplished little by doing so, for on the pure-research front, Hampson continued to assist Ramsay, Rayleigh, and their aide Morris Travers in isolating the remainder of the noble gases. And on the commercial front, Hampson also forged ahead.

The first several steps in the liquefaction cascades could now be commercially replicated. Combined with the Linde and Hampson patented processes of 1895, these cascade steps made it possible to use cold to manufacture liquid air and separate from it liquid oxygen and liquid nitrogen, also producing liquid traces of many other elements and compounds. In short, while the scientists of the pure-research laboratories pursued rare gases such as argon and helium, the commercial scientists and technologists tried as hard as they could to make liquefied gases the stuff of everyday life.

The first major technology of the cold, for refrigeration, was spreading, especially in America. Back in the 1840s, John Gorrie had wanted to use refrigeration of air to "counteract the evils of high temperature, and improve the condition of our cities," through the use of central refrigeration plants that would pipe cool air to homes and businesses. Centuries earlier, Drebbel had proposed something similar for heat distribution in London. By 1889, cooled air piped from a central station was available in New York, Boston, Los Angeles, Kansas City, and St. Louis; in the latter city, the proprietor of the Ice Palace restaurant had such frosty air piped in that in addition to cooling his customers he was able to use it to spell out his name in ice on his window; he reinforced the cold's effect by wall murals of scenes from polar expeditions. The exceptionally mild winter of 1890, during which relatively little natural ice formed, spurred the further progress of artificial icemaking by intensifying demand for
mechanical refrigeration among manufacturers of various products. But all those who wanted better refrigeration had to await the development of more efficient and less dangerous coolants.