Marie Curie - Kathleen Krull [11]
Indeed she was, despite one big problem. Marie had no lab of her own. Pierre solved it by arranging for her to take over a drafty, drab storage space at his school. A closet, really. (On cold days, the room’s temperature could drop as low as a frigid forty-four degrees.) Still, it was all hers, a lab she was essentially starting from scratch. Had she worked in a fancy setup within the scientific establishment—say, at the Sorbonne—she might have had to focus on what professors told her to do. Here she was out of the loop, free to explore what she pleased: Becquerel’s rays. Passing her during the day, Pierre sometimes would stop to caress her hair.
Pierre was busy with his own work on crystals. Beyond that, his electrometer device was of critical help to her now. With it, Marie could measure very small currents of electricity that the weaker rays of uranium produced.
Pierre also helped Marie construct a chamber out of old wooden grocery crates. Inside they placed two circular metal plates, one at the bottom with a positive charge and another with a negative charge three centimeters above it. A thin layer of uranium was placed on the lower plate.
Marie already knew that the uranium rays would make the air conduct an electric current to the top plate. The more radiation, the stronger the current would be. Using the electrometer to measure the strength of the electric current, she could work out how much radiation was being emitted.
What she discovered was that the amount of uranium was the sole factor determining the amount of radiation emitted (and also the strength of the electric current). Nothing else mattered—not changing the temperature of the uranium, for instance.
The work required incredible dexterity and concentration, painstaking hours of sitting in one position using very precise devices while manipulating a stop-watch and weights. Think of someone juggling while reading a newspaper and you get some idea of the multitasking involved. But this was a job tailor-made for Marie Curie, so careful a worker that at the Sorbonne she was known for never shattering glass tubes the way other students did. She succeeded in obtaining the measurements that gave her the relative power of the uranium.
Now that she’d measured the amount of radiation given off by uranium, the next question was: did other elements besides uranium emit these strange rays? The only way to find out was to examine all the known elements. very persuasive when she needed something for her work, she begged and borrowed samples of elements from other scientists, including some of her old professors. She now went through Mendeleyev’s periodic table of elements, testing them one by one. The mystery rays weren’t just peculiar to uranium—she discovered that they came in a weaker form from thorium (a mineral element discovered in 1828) as well. Her findings were that only the elements uranium and thorium gave off this radiation.
In April of 1898, Marie made a report to the all-important French Academy of Sciences. The eminent men at the meeting listened to a report on frog larvae. Then Marie’s report, called “Rays Emitted by Uranium and Thorium Compounds,” was read aloud by one of her professors. She couldn’t read it herself because she wasn’t a member—no women were allowed. Then came a report on hydraulics. . . .
Marie returned to the lab and kept experimenting. Now that she had tested all the elements for Becquerel rays, she turned her attention to compound minerals, ones containing some uranium and thorium.
She tested ores just as she had tested each element. Her interest was piqued in particular by a heavy black ore called pitchblende. Pitchblende contains a huge variety of minerals, including uranium and thorium. What she discovered was intriguing: pitchblende gave off four to five times more rays than could have been predicted by the amount of uranium and thorium in it.
Why?
Her leap in thinking was straightforward and