Tuesday, February 28, 2017
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Working through Pitchblende to Separate Radium & Polonium

In the previous article we talked about the scientific breakthrough - discovery of polonium and radium. Marie and Pierre had still a long way to go to prove that they really discovered new elements. The amount of radium and polonium which they were able to extract were minute, they needed much more in order to establish their physical and chemical properties.

The ore from which they extracted polonium and radium came from the pitchblende deposits used to extract uranium salts for glass manufacture in St Joachimsthal mine in Bohemia. The price of pitchblende was high but the value of the residue left after extracting uranium salt was low since the ore was considered useless.  In that time St Joachimsthal was a part of Austrian empire. There were many  problems to deal with:  to arrange a permission to transfer massive amounts of ore from Austria to France, to pay for the ore and to for its transportation. Besides, Marie and Pierre did not even have a good quality laboratory at the Sorbonne University, only a small shack with no floor which was used for animal dissection in the past.

Marie and Pierre in the laboratory

Curies were very lucky, although they could not count on French government or Sorbonne's officials they got help directly from Austria. The reply for their request to obtain the residue ore was positive. First of all the residue - a material considered useless after extracting Uranium salt, was not scattered around but piled up near the mine. Second of all the Austrian government, thanks to intercession of prof. Suess and the Academy of Science in Vienna, decided to give a ton of ore to Curies for free, although they had to pay for the transport and if they needed more they could get in on the best terms.

The ton of pitchblende ore (dull brown mixed with some pines from Bohemia) was soon delivered in front of the School of Physics in Paris one morning. Curies were excited. The next 4 years of their life (1898-1902) will be devoted to separating radium and polonium from the ore and studying their properties. This was quite a heavy task considering that the shed they were working was a hothouse during the summers, but it was leaking from rain and cold during the winters.

Marie and Pierre decided to split their duties. Whereas Pierre tried to determine the properties of newly discovered elements, Marie decided to do the man's job - she was treating the mass amounts of the raw ore material with precipitates and liquids in order to separate measurable amounts of radium and polonium.

In spite of this arduous job this was a happy time for Curies. They shared the excitement of what they will be able to find, they believed that there are on the road to great discovery. Marie and Pierre spent long hours together in the laboratory, but they also tried to spent valuable time with Irene, which was growing up quickly. Irene was under a care of Pierre's father during the day. During 1899 and 1900 they published reports of a discovery of "induced radioactivity" due to radium, another on the effects of the radioactivity and also on the electric charge carried by the rays.

There was lots of competition in the radioactivity field development in this time, the Curies needed the coworkers. Andre Debierne became the most famous of their assistant. He later discovered a new element, actinium.

Lots of the laboratory work, if the weather permitted, was done outdoors in order to avoid fumes since there was no any ventilation system in the shed. Eventually more and more concentrated products were obtained.  Marie was working on the very final stage of the fractional crystallization. Finally in 1902, forty five months after the existence of radium was announced by Curies, Marie was able to separate 1 decigram (o,1 g) of pure radium. The Curies were able to determine the atomic element of the new substance, 225. Now we know that since radium consists of several radioisotopes its atomic number will not be an integral.

In that time when Curies were working on radium separation, nobody was aware of the dangerous effects of the radiation exposure. Pierre and Marie by working with concentrated radium from the ore as a final product were exposed to harmful doses of radiation which affected their physical state. They were often tired, without knowing that the radioactivity is harmful for their bodies. Just for a comparison, Uranium-238 (the most common radioisotope of uranium,) radioactivity is about 3 mln times less than Ra-226 (the most common isotope of radium).  In that times though Marie and Pierre were perplexed by a beautiful bluish color emanation from radium, they considered is a magic, but they did not realize how harmful it may be for their own bodies.

We will continue Marie and Pierre story in the next Polish-American Journal issue.

Baba Jaga Corner: Visit Jaga Polish Culture Website at: www.polishsite.us


Eve Curie "Madame Curie"

Barbara Goldsmith:" Obsessive Genius"



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