PLUTONIUM — SEABORG 211 



The Plutonium Project of the Manhattan District was organized for 

 the purpose of producing this isotope, the explosive ingredient for the 

 atomic bomb. The first isolation of pure Pu^^^ and the early study of 

 its chemistry and the design of the chemical process for its large-scale 

 separation from uranium and fission products, which involved work on 

 the ultramicrochemical scale with only microgram amounts of material, 

 have been described in previous discussions. 



The availability of the relatively large amounts of plutonium, as the 

 result of the successful operation of the chain-reacting uranium piles, 

 has made it possible to make a complete investigation of its chemical 

 properties using methods which can be considered to be those of ordi- 

 nary chemistry except for the health precautions which are necessary. 

 This work has established that plutonium has the oxidation states VI, 

 V, IV, and III, and that there is a shift in stability toward the III 

 state as compared to neptunium and uranium. A large number of 

 compounds of plutonium have been prepared and their properties 

 determined. It may be said that the chemistry of plutonium today is 

 as well or better understood than is that of most of the elements in 

 the periodic system, even though its chemistry is very complex as can 

 be judged by the multiple oxidation states. 



Because of its relatively high specific a-radioactivity, amounting to 

 about 140,000,000 a disintegrations per minute per milligram, special 

 equipment and special precautions are necessary in the investigations 

 of its properties. This high a-radioactvity makes it expedient to con- 

 tinue to use rather small amounts — that is milligram amounts — for a 

 number of these investigations even though large amounts might be 

 available. Even if there were no other reasons, its high a-radio- 

 activity places plutonium outside of the class of elements which might 

 eventually find widespread distribution among chemists for investi- 

 gation of its chemical properties. 



As I have indicated earlier, the question as to the existence of trans- 

 uranium elements in nature has long been a matter for speculation and 

 investigation. It was also indicated that it is now almost certainly 

 known that these elements do not exist in appreciable amounts on the 

 face of the earth. I would like to discuss this matter further because 

 it is true that one of these elements, plutonium, has been experimentally 

 found to exist in nature in minute amount. 



The knowledge of the chemical properties of neptunium and plu- 

 tonium which had become available as a result of the discovery and 

 study of these elements made it possible to conduct very effective 

 searches for these elements in various minerals. Early in 1942 G. T. 

 Seaborg and M. L. Perlman in Berkeley undertook a search for these 

 elements in pitchblende ore, the primary purpose at that time being 

 to establish whether such a source of a fissionable transuranium isotope 

 might serve as a practical source capable of substituting for the, at that 



