The hundred or so eminent scientists and diplomats who had assembled for the ceremony had no trouble recognizing the visitor as she walked into the East Room of the White House on the arm of President Warren G. Harding. After all, having won two Nobel Prizes, Marie Curie was probably the most famous woman in the world! Now she was about receive a very special gift from America, a small beautifully crafted mahogany box, inside of which was another lead-lined steel box, inside of which was…nothing. The intended contents were deemed to be too dangerous to be brought to the White House and would be placed in the box just before it was to be shipped to France. The box, draped in red, white and blue ribbons, had been constructed to hold a most precious cargo. Marie Curie’s gift from the American people was to be a gram of the radioactive element radium, valued at a stunning $100,000! ($1.25 million in today’s funds)
It might seem to have been a curious gift, seeing that it was Curie who had discovered radium in the first place. But discovery and production are two different matters. Indeed, one of the most astonishing features of Marie Curie’s discovery was that tons of pitchblende had to be processed to yield a few micrograms of radium. The special properties of the new element immediately sparked the interest of physicians who as early as 1902 began to tout radium as a treatment for everything from warts and infertility to cancer. Marie Curie herself was a very vocal advocate of “telecurie therapy,” the placement of small vials of radium around the site of a cancer with hopes that the radioactivity would shrink the tumour. Sometimes it did. To explore this further, Curie needed more of the element which at the time was being produced commercially in the U.S. from an ore found near the Grand Canyon. Isolation was an arduous business and at the time of the one gram gift to Marie Curie, the total U.S. supply was only about 50 grams.
Radioactivity was Marie Curie’s baby. In fact it was she who had coined the term to describe the mysterious rays discovered in 1896 by the French physicist Henri Becquerel. At the time, uranium oxide was sometimes added to pottery or glass because of the yellow-green fluorescence it produced and Becquerel wondered if this light-induced fluorescence was akin to those wondrous X-rays recently discovered by Wilhelm Roentgen. As often happens in science, Becquerel came upon a phenomenon that was quite different from what he was looking for. One day he unwrapped a photographic plate that had been stored in a drawer and was mystified to see streaks as if it had been exposed to light. Noting that a sample of uranium oxide had been stored on top of the plate, Becquerel concluded that it must have given off some sort of rays that were capable of penetrating the black wrapping paper.
The initial excitement generated by Becquerel’s “uranic rays” quickly faded, and may have passed into obscurity had Marie Curie not been looking for a topic for her PhD thesis. She was intrigued by these rays continuously emanating from uranium, apparently providing an inexhaustible supply of energy. They were mysterious, novel, and very little had been written about them. An ideal topic for doctoral research!
Becquerel had previously found that air exposed to “uranic rays” became a better conductor of electricity, a phenomenon that had also been noted with X-rays. Both types of radiation were capable of “ionizing” air’s oxygen and nitrogen molecules, in other words, they were capable of knocking off electrons, leaving behind positive ions. The liberated electrons produced a current. As chance would have it, Pierre Curie, the brilliant physicist whom Marie had married in 1895 had developed the electrometer, a device for measuring the very feeble currents that can travel through ionized air. The Curies now had a way of quantitatively measuring radiation.
Marie began by examining all the known elements but found only one other, thorium, that like uranium, was radioactive. She also studied a variety of minerals and discovered that pitchblende, the ore from which uranium was extracted, produced far more radioactivity than could be accounted for by its uranium content. The ore therefore had to contain some other, yet unknown, radioactive element. But there could not be very much of it since more than 99% of substances in the ore had been previously identified.
Now began the tedious process of chemical separation. The Curies began with several tons of pitchblende and using a variety of classic precipitation reactions laboriously separated the components, checking all batches for radioactivity with Pierre’s electrometer. Within a year, Marie managed to isolate a few micrograms of not one, but two new elements, both of which were powerfully radioactive. She named one “radium” after the Latin “radii” for rays, and the other “polonium” after Poland, her country of birth.
Few discoveries have had as much impact on the world as the Curies’ and Becquerel’s work on radioactivity. The discoveries opened the door to understanding the structure of the atom, to radiation therapy for cancer, and to the use of nuclear energy. The three shared the 1903 Nobel Prize in physics, and in 1911 Marie Curie was awarded a second Nobel, this time in chemistry, for the discovery of polonium and radium. In recognition of the 100th anniversary of Marie Curie’s Nobel Prize, the United Nations chose 2011 as the International Year of Chemistry.
Madame Curie could have profited richly from the discovery of radium, but decided not to take out a patent, maintaining that “radium is not to enrich anyone, it is for all people.” Unfortunately the gift with which she had enriched society ended up taking her life. Marie Curie died of radiation-induced leukemia.
And what happened to the famous mahogany box she received from President Harding in 1921? It resides in the Curie Museum in Paris, a silent testimonial to “the woman who opened the nuclear age."
