Chemistry

How Marie and Pierre Curie Discovered Polonium and Radium



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In November 2006, Alexander Litvinenko, a former KGB agent who had been granted asylum in the United Kingdom, took 3 weeks to die of radiation poisoning from polonium.  Polonium’s discoverers, the Curies, would have been horrified.  As Marie Curie once said, “I am one of those who think like Nobel, that humanity will draw more good than evil from new discoveries.”  

We need to take a closer look at how Marie and Pierre Curie discovered polonium and radium before we can decide whether she was right or if, perhaps, it might have been better that the discoveries that ushered in the Atomic Age had never been made.

Paris and the Sorbonne

It was good to be a scientist in France in the 1890s.  The nation was midway through the Third Republic, relatively stable and prosperous.  A new educational establishment had grown up, and scientists no longer had to support themselves from their own resources or with a “day job.”  

Before the Revolution, the ancien régime had refused to allow anything new.  The young French thinkers of the Enlightenment thus were relieved of any need to consider the practical consequences of their new ideas, and so they kept asking deeper and more daring questions, getting down to basic principles.

G. K. Chesterton described it this way in “The Blue Cross”:  “Aristide Valentin was unfathomably French; and the French intelligence is intelligence specially and solely...he was a thinking man, and a plain man at the same time. All his wonderful successes, that looked like conjuring, had been gained by plodding logic, by clear and commonplace French thought.   The French electrify the world not by starting any paradox, they electrify it by carrying out a truism...[E]xactly because Valentin understood reason, he understood the limits of reason.”

Now that the stifling regime had been swept aside and the resulting turmoil had settled down, France was indeed expanding the limits of reason on a scale matched nowhere else in the world at that time.

The university system in Paris where most of this happened was (and still is) quite complex.  Although generally referred to as the Sorbonne, it has always been made up of many institutions.  Charles Dickens wrote, “During the revolution at the end of the last century, the Sorbonne was suppressed, and in 1808 the old college was given to the University of Paris. By a royal decree passed, in 1821, the Sorbonne was henceforward to be used for the purpose of Public Instruction, and within its walls were established the Faculties of Theology, of Letters, and of Sciences. It was ordained that public lectures should be given upon these subjects; and now the Sorbonne is supposed to be the headquarters of the Academical University of Paris. The lectures in the Sorbonne are free to anyone who likes to go. Women who wish to attend lectures go as a rule to the College de France.”

The College de France was one of the university’s most advanced institutions, and 24-year-old Marie Sklodowska, from Warsaw, was there to get her teaching diploma.  In 1893, two years after coming to Paris, she took her degree in physics, and the next year she came in second in a mathematics degree.  But now she had a little problem.

Two outsiders come together

An industrial society had ordered a study from Ms. Sklodowska on the magnetic properties of various steels, but she had no room for the equipment this would require.  Marie mentioned this to a friend, and he referred her to “a scientist of great merit who works in the School of Physics and Chemistry,” one Pierre Curie.

Pierre was eight years older than Marie and had been awarded the equivalent of an American master’s degree in physics at age 18.  Together with his brother he had already discovered the piezoelectric effect, and now he was doing extensive research on magnetism.  However, like Marie, he had been educated at home and had none of the elite networking contacts that were needed to get ahead in the academic world, so his position at the School of Physics and Chemistry was really just that of laboratory chief.

Things happened quickly once Marie and Pierre met in 1894.  He helped her get the laboratory space she needed.  These two brilliant people, who until now had existed on the very fringes of the Paris academic world, then fell in love and became a working research team.

Marie encouraged Pierre to turn his work on magnetism into a doctoral thesis, and a few months before their marriage in 1895, he was awarded his doctorate of science.  In 1896, Marie passed her teacher’s diploma, coming in first.  In 1897 she completed her studies on magnetic properties of various steels.  In September of that year, she gave birth to their first child, Irene.  Once she recovered from that, she returned to work.

The next logical career step was to get her doctorate.  She looked through recent experimental results and found something interesting that fellow scientist Henri Becquerel had published the previous year.

The discovery of polonium and radium

Becquerel, while studying X-rays, had accidentally discovered that uranium salts gave off what Marie called “rays of a peculiar character.”  She chose to make the investigation of these rays the topic of her thesis.

She used piezoelectric-based equipment designed by Pierre to measure the tiny amounts of energy that were being released by uranium and, as she soon found, also by thorium.  Marie started to study uranium and thorium ores and was surprised to find that pitchblende was much more active than it should be from its uranium content.  There had to be another radioactive element in pitchblende, one that had not yet been recognized.

At this point, Pierre gave up his own work and joined Marie in the hunt for the new element.  After much chemical analysis, they ended up with something that was about 300 times more active than uranium and called it ‘polonium’ in honor of Marie’s native land.  A few months later they discovered another new radioactive element that they called ‘radium.’

Marie and Pierre now had to produce these new elements in measurable quantities in order to prove their existence.  This meant processing tons of pitchblende by hand, and the only lab they could get for this work was a little outdoor shed.

After a year, they realized that radium was easier to separate out than polonium, and so they concentrated on that.  Finally Marie was able to collect about 1 decigram (or 0.0035 ounce) of almost pure radium chloride.  Her thesis, presented on June 25, 1903, was described by the committee as the greatest scientific contribution ever made in a doctoral thesis.

Good or evil

Medical uses for radium were recognized immediately, and while new isotopes that are easier and safer to use have replaced radium in some cancer treatments, those isotopes never would have been discovered without the Curies’ initial work. Many people have also been sickened from radioactivity.  Marie died of aplastic anemia (Pierre was killed in a traffic accident).  Their daughter Irene, who became a researcher, may have died from polonium exposure years after a small vial of it exploded near her. Alexander Litvinenko was the next person to die from polonium ingestion.

Marie Curie also said, “Nothing in life is to be feared, it is only to be understood. Now is the time to understand more, so that we may fear less.”

The story of the Curies’ discovery of polonium and radium is a wonderful example of love and intelligence working together to expand human knowledge.  Their results have been used for both good and evil, but perhaps we can use their example to do a little research of our own into ways to maximize the good and minimize the evil.  Once we understand how to do that, we will have less fear of living in the nuclear age that they and others bequeathed to us.

Sources:

“Madame Curie: a biography.”  Eve Curie

“Marie and Pierre Curie and the Discovery of Polonium and Radium.” Nobel Prize Web site

“Pierre Curie”  by Marie Curie.

“The rise and decline of France as a scientific centre.”  Joseph Ben-David.  (full article)

Science in France in the Revolutionary Era.”  Thomas Bugge and Maurice P. Crosland (introduction only)

History of France in the 19th Century (Wikipedia)

History of France in the 19th Century (Wikipedia)

Dickens's Dictionary of Paris 1882:  An Unconventional Handbook Charles Dickens.

College de Sorbonne. (Wikipedia)

Polonium. (Wikipedia)

“The Blue Cross.”  Gilbert K. Chesterton


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