Chapter Five

ANDRÉ (Actinium)

BY THE CURIES’ count, there were now four “radioelements”—uranium, thorium, polonium, and radium. Most other scientists, however, recognized only the first two.

The mere wisps of polonium and radium that the Curies had pried from pitchblende were too minute for the weight calculations or other experiments that would bolster any claim to element status. They had nothing but their radioactivity to show for themselves, plus one lone spectral line. And yet, on photographic plates—the medium in which uranic rays had first made their presence known—the Curies found that polonium and radium could produce in half a minute the same effects that uranium and thorium required hours to achieve.

“In our opinion,” Marie wrote in a reflection on her joint work with Pierre, “there could be no doubt of the existence of these new elements, but to make chemists admit their existence, it was necessary to isolate them.” The couple would need much larger supplies of raw material for this next phase. Marie’s early estimate of a 1 percent polonium content in pitchblende had been wildly optimistic. Since sizable lumps of pitchblende had yielded only barely discernible traces of the desired end products, the proportion by weight veered toward one-thousandth or even one-hundred-thousandth of one percent. And so, instead of a mere hundred grams of pitchblende, they now ordered one hundred kilograms (about 220 pounds) from the mine in Bohemia and paid for it with Marie’s prize money.

Clearly their operations would no longer fit into the tiny lab space on the ground floor of the industrial school. Once again the accommodating director, Paul Schützenberger, found room for Marie’s activities. Across the courtyard from the school stood an old wooden shed that had once served as an anatomy theater for medical students. A cast-iron stove, a blackboard, and a few worn pine tables were the only furnishings left in the place, which looked more like a hangar than a laboratory. It had an asphalt floor and a glass roof that leaked.

A century would pass before the term “glass ceiling” gained currency as a metaphor for invisible barriers to women’s advancement, but Marie Curie toiled under an actual glass ceiling from 1899 to 1902, the years she spent in that “poor, shabby hangar,” spinning pitchblende into radium.

Because the shed lacked ventilation hoods for carrying off poisonous gases, the Curies handled the first stages of the chemical treatments outdoors in the courtyard, where natural breezes did the ventilating for them. When rain drove them indoors, they continued their extraction procedures, “leaving the windows open.”

The Curies’ hangar in the courtyard on the rue L’homond, 1899

Musée Curie (coll. ACJC)

The prohibitive purchase price of pitchblende might have stymied them, but they soon hit on a way to economize: In place of the raw ore, which contained the commercially valuable uranium, they would settle for mine leavings already picked clean of uranium. A sympathetic colleague in the Vienna Academy of Sciences entreated the Austrian government on the Curies’ behalf. The state-run uranium mine in Bohemia, which had been dumping its tailings in the nearby woods, agreed to ship the French scientists as much of the worthless stuff as they wanted, charging them only the cost of transport.

In the spring of 1899, a load of depleted pitchblende ore traveled to Paris by rail freight, covering the final leg from the Gare du Nord to the industrial school on a coal-delivery wagon. As soon as the shipment arrived, Marie rushed outside to cut open one of the big burlap sacks and dig her hands into the dusty brown powder. She found it full of pine needles from the forest floor where the waste had lain discarded.

At the mine the ore had been crushed, then roasted with carbonate of soda, washed with warm water, and bathed in sulfuric acid to capture the desired uranium in solution. The residue relegated to the Curies thus came somewhat predigested, but not really prepared for the extraction of radium. Everything they had done on a small scale in the school’s laboratories now needed to be scaled up. “I had to treat as many as twenty kilograms of material at a time,” Marie reported, “so that the hangar was filled with great vessels full of precipitates and of liquids. It was exhausting work to move the containers about, to transfer the liquids, and to stir for hours at a time, with an iron bar, the boiling material in the cast-iron basin.” Nights found her “broken with fatigue.”

She interspersed the brute effort of breaking down pitchblende with the more delicate, less physically taxing work of fractional crystallization—repeatedly dissolving and distilling residues to achieve ever-higher concentrations of radium, which made its presence known by demonstrating radioactivity in the ionization test chamber. “The very delicate operations of the last crystallizations were exceedingly difficult to carry out in that laboratory,” she said, “where it was impossible to find protection from the iron and coal dust.”

Early on, Pierre had confided to Marie that he hoped their new elements would display beautiful colors. Now, as though in answer to his wish, the beakers of solutions and crucibles of crystalline precipitates surrounded themselves in haloes of soft bluish light. Their glow held the couple spellbound. Many an evening they returned to the shed after dinner to gaze at “our precious products” arranged in flasks and crucibles on tables and boards. “From all sides we could see their feebly luminous silhouettes, and these gleamings, which seemed suspended in the darkness like faint fairy lights, stirred us with ever new emotion and enchantment.”

By the light of such alluring illumination, they came to realize the true length of the road ahead: They would need several tons of mine waste to arrive at a weighable quantity of either of their new elements. Pierre thought the task too onerous and perhaps even unnecessary. He preferred to turn all his attention to ascertaining the properties of radium, while Marie continued pouring her effort into accumulating more radium—a process that required fewer chemical reactions than the isolation of polonium.

New aid came to them in July 1899 in the person of André Debierne, a young chemist who had attended Pierre’s school. Debierne now worked as a lab assistant at the Sorbonne, just as Pierre had done early in his career. The Curies challenged him to raise the techniques they had pioneered to a quasi-industrial level of production. At the same time they forged a new deal with the organization that manufactured and sold Pierre’s scientific instruments, the Société Centrale des Produits Chimiques. The Société would take over the bulk of preliminary chemical treatment, as directed by Debierne, in exchange for some of the fruits of the Curies’ labor—that is, a share of the radium.

Marie and Pierre Curie in their laboratory

Photo Albert Harlingue. Musée Curie (coll. ACJC)

LATER THAT SUMMER Marie showed her husband and daughter the splendors of her native country. The three of them got together with her father and the families of all her siblings on the picturesque mountainside near Zakopane where Bronya and Kazimierz were building their new sanitarium. At this Sklodowski reunion, Pierre endeared himself to his in-laws by joining their conversations in halting Polish.

By autumn, an entire ton of pitchblende waste had been preprocessed by the staff at the Société Centrale. Debierne, in addition to overseeing this phase of the work, simultaneously obeyed the Curies’ directive to probe the ore for new radioelements, as they had done, by trying different breakdown procedures and testing for radioactivity at every stage. He claimed his own find in October 1899. Since the Latin word for “ray” had already been appropriated by radium, the proud discoverer borrowed the Greek equivalent to form the name “actinium.”

Although Debierne continued to work in his lab at the Sorbonne, he became a frequent presence in the Curies’ shed, and also at their new home. In early 1900 they moved to a rented stucco house on the boulevard Kellerman, where Pierre’s father tended a garden, and friends gathered on Sundays for casual scientific discussions. Irène learned to call Debierne “Uncle André.”

The Curies’ stepped-up production practices put them in the unique position of being able to lend out radioactive materials to other scientists, including Henri Becquerel and several physicists in England, Germany, and Austria, who had read of radium in the Comptes rendus, the weekly journal of the Académie des Sciences, and initiated their own experiments in radioactivity. Appreciative notes from these grateful recipients agreed that the quality of the Curies’ samples promised the best research outcomes, the greatest likelihood of observing otherwise undetectable phenomena.

One day Becquerel absently tucked a sealed glass tube of active material into his vest pocket and developed a burn on his torso in the shape of the tube. The incident, he said, slightly tainted his love for radium. Pierre then intentionally exposed the skin on his own arm, and documented the wound’s slow healing process in a report published in the Comptes rendus. Both he and Mme. Curie, he noted, often found that the palms of their hands flaked and peeled in response to handling radioactive products, and the tips of their fingers hardened painfully for weeks or months at a time. These discomforts did not worry them or deter them from pursuing their science. In fact, their reported skin lesions aroused the interest of medical doctors, who now looked to radioactivity as a potential palliative for certain dermatologic diseases and even as a means of destroying cancerous tumors.

Excitement surrounding the radioelements bubbled over at the first International Congress on Physics, held in Paris in the summer of 1900 to coincide with the world’s fair. On the afternoon of August 8, in an amphitheater at the natural history museum, Pierre summarized all that he and Marie had accomplished to date, while also acknowledging the work of others whose insights and projects were expanding the general understanding of radioactivity. Ernest Rutherford, for example, a young New Zealander studying under J. J. Thomson at the Cavendish Laboratory in Cambridge, discovered through experiments with uranium that uranic rays were of two distinct types. The ones he dubbed “alpha rays” played the primary role in ionizing gases, but they did not travel far and could be blocked altogether by a sheet of paper. The “beta rays,” on the other hand, ionized only weakly but were extremely penetrating. They could pass through metal screens and cover considerable distances. Adherents of the new science had also learned that radioactivity was contagious: an active source such as radium could render other objects radioactive, too, at least temporarily. This “induced radioactivity,” Pierre said, had contaminated just about everything in the Curies’ lab.

Before closing, Pierre stressed the gross disproportion between the infinitesimal quantities of the new radioelements and their enormous activity. He and Mme. Curie, by the chemical methods they employed, had processed several tons of pitchblende to retrieve only a few fractions of a gram of each active material. These products, though still not fully isolated, already showed themselves to be at least one hundred thousand times more radioactive than pure uranium.

ALTHOUGH THE CURIES’ professional standing and reputation were rising rapidly, their income barely covered their expenses. In 1900 the University of Geneva tempted Pierre with a lucrative physics professorship, also promising him a real laboratory and an adjunct research position for Marie. He accepted, then rejected the Geneva offer, opting instead to remain in France and earn extra money by teaching a course in physics for medical students at the Sorbonne. Marie, too, took on paying work. Four years after earning her teaching certificate, she joined the faculty at Paris’s best girls’ school for aspiring instructors, the École Normale Supérieure d’enseignement secondaire de jeunes filles at Sèvres. She described her pupils as “girls of about twenty years who had entered the school after severe examination and had still to work very seriously to meet the requirements” of the lycées where they hoped to teach.

Marie’s students initially tittered among themselves and mocked her Polish accent, but they soon came to anticipate her classes with excitement. “We watched from our windows for the arrival of the professor,” one alumna remembered, “and as soon as we saw her little grey dress at the end of the allée of chestnut trees we ran to take our seats in the conference room.”

Traveling to the Sèvres campus several times a week by tram took Marie away from the hangar and slowed her progress toward the determination of radium’s atomic weight.

At the time of the announcement of radium, in 1898, the Curies’ most active sample consisted mainly of barium chloride, with a soupçon of radium too small to be weighed. Since then, Marie had been assiduously amassing more and more radium by sifting additional ton-quantities of pitchblende residue sent from the mine in Bohemia. In March 1902, toward the end of her second year of teaching, she finally attained enough material to attempt the atomic weight measurement that would establish radium as a bona fide element in the eyes of Mendeleev and other chemists.

Her hard-won treasure was a single centigram of pure radium chloride. Spectroscopy by Eugène Demarçay assured Marie that her sample contained only radium and chlorine bound together in chemical combination as the final stage of her fractional crystallizations. It was technically a salt, distantly related to common table salt. It boasted a million times the activity of uranium.

As small as the sample was (only one-hundredth of a gram), the quantity of radium it contained was smaller still. To pin a definitive atomic weight on radium, she would have to put the sample through several chemical reactions involving elements of known atomic weight, and then calculate accordingly.

Marie weighed her precious, perfectly pure radium chloride several times on a Curie aperiodic balance (accurate to the twentieth of a milligram) and averaged the results. Then she dissolved the sample together with silver nitrate, and the interaction caused the constituents to change partners, yielding silver chloride and radium nitrate. She dried and weighed the silver chloride (a few times over). Then she reversed the reaction to reconstitute the radium chloride and made sure nothing had been lost in the various manipulations. Knowing the accepted atomic weight of silver to be 107.8, and that of chlorine 35.4, she could now assess how much of her radium chloride’s weight belonged to chlorine. The remainder was radium, to which she assigned an atomic weight of 225, plus or minus 1.[1] The number stood alone, unaccompanied by grams or other units, since it represented the weight of a single atom—an entity that could not be weighed on any sort of scale. The 225±1 figure, nearly double the atomic weight of barium, offered further gratifying proof of radium’s individuality.

In May, Marie communicated this important result to her father. “And now you are in possession of salts of pure radium!” he replied. “If you consider the amount of work that has been spent to obtain it, it is certainly the most costly of chemical elements!” This was true, yet the professor seemed unable to grasp the wider importance of his daughter’s finding: “What a pity it is,” he continued, “that this work has only theoretical interest.” Days later, when a telegram informed Marie that a sudden illness had stricken her father, she hurried to Warsaw but arrived too late to see him alive. She clung to her siblings at the funeral, and in September she went again to Poland to reaffirm the family closeness.

Having demonstrated the reality of radium, she spent the next several months preparing her doctoral thesis, describing her years of “Researches on Radioactive Substances” that had since given rise to a scientific movement. On the day of her dissertation defense, June 25, 1903, she appeared at the Sorbonne students’ hall wearing the new black silk-and-wool dress that Bronya, visiting for the occasion, had made her buy. The family—Bronya, Pierre, and old Dr. Curie—sat at the back of the crowded room near a coterie of Sèvres students. Marie had invited these young women to attend, in the hope that their presence would embolden her, and also with the goal of showing them where their own studies might lead.

In addition to her mentor Gabriel Lippmann, the three-member faculty jury seated at the oak table included chemist Henri Moisson, who had supplied her with her earliest samples of uranium, and physicist Edmond Bouty. She stood before them, occasionally augmenting her answers to their questions with an equation or diagram sketched on the chalkboard. At length they congratulated Mme. Curie on her historic success as the first woman in France to receive the PhD degree in physics. Automatically she became the first wife—as well as the first mother—to own that achievement. And although most of the audience remained ignorant of the fact, she was also the first person to defend a dissertation while pregnant.

The baby came early—much too early, in Marie’s fifth month of pregnancy, during the family vacation on the Île d’Oléron off the southwest coast.

“I am in such consternation over this accident,” she wrote of her miscarriage to Bronya in late August. “I had grown so accustomed to the idea of the child that I am absolutely desperate and cannot be consoled. Write to me, I beg of you, if you think I should blame this on general fatigue—for I must admit that I have not spared my strength.” In addition to her research, her teaching, her thesis preparation, her care of Irène, and her household duties, she had traveled to London with Pierre in early June, when he lectured at the Royal Institution. “I had confidence in my constitution, and at present I regret this bitterly, as I have paid dear for it. The child—a little girl—was in good condition and was living. And I had wanted it so badly!”

Months later, the Royal Society awarded the Curies the prestigious Davy Medal, named in honor of chemist Sir Humphry Davy, for their outstanding contributions to the field of chemistry. Pierre went alone to London to collect the gold medallion and the £1,000 that came with it. Marie, still weak after her miscarriage, had developed the grippe and a lingering cough, but, as she assured her brother in December, she was merely anemic, with no signs of tuberculosis.

A few paragraphs into her newsy letter, she casually mentioned another recent accolade: “We have been given half of the Nobel Prize.” Only lately established in 1901, the Nobel Prizes reflected their founder Alfred Nobel’s own varied interests. A scientist, engineer, entrepreneur, poet, and dramatist, Nobel had willed his fortune to the rewarding of merit in physics, chemistry, medicine, and literature. And because his invention of dynamite had exacerbated the carnage of war, he endowed a separate prize for peacemakers.

The Royal Swedish Academy awarded the first Nobel Prize in Physics to Wilhelm Roentgen for revealing the existence of X-rays. Roentgen had been chosen over Marie and Pierre Curie, whose names were put forward that year by the influential French doctor Charles Bouchard, apparently because of radioactivity’s medical potential. The Curies were nominated again in 1902 by two physicists—Gaston Darboux of France and Emil Warburg of Germany—but were again passed over. Early in 1903, Pierre received word from one of the nominators that he alone—and not Marie—would likely share the physics prize with Henri Becquerel for the discovery and study of radioactivity. “This would be a great honor for me,” he replied, “however I should very much like to share the honor with Mme. Curie, and for us to be considered jointly, in the same way that we have done our work.” He reiterated the details of that work to clarify Marie’s role, and at length the physics committee agreed to include her.

Of the three joint winners of the 1903 Nobel Prize in Physics, announced in mid-November, only Henri Becquerel attended the formal ceremonies in Stockholm on December 10, the anniversary of Alfred Nobel’s death. Pierre expressed the couple’s thanks to the Swedish Academy by letter, but regretted they could not possibly travel at that time. As Marie explained to Józef, “I did not feel strong enough to undertake such a long journey (forty-eight hours without stopping, and more if one stops along the way) in such an inclement season, in a cold country, and without being able to stay there more than three or four days: we could not, without great difficulty, interrupt our courses for a long period.”