254 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1959 
TO Cl» SUPPLY: 
Tree 
TO VACUUM 
CHLORINE RESERVOIR 
COOLING BATH 
B 
QUARTZ Cc 
AIR JET S g 
PLUTONIUM 
ME TAL 
CLOTH: WICK WET WITH Hp 
—_—————- THERMOCOUPLE 
is COPPER BLOCK 
Ficure 3.—Apparatus used in the first preparation of PuCl; (February 1944). The com- 
pound was prepared by treating a 50-ug piece of plutonium metal with chlorine gas. 
After placing the plutonium in the capillary tube, the system was evacuated. Chlo- 
rine gas was added, and a small amount condensed in a reservoir as shown. The sys- 
tem was closed and remained filled with chlorine at a pressure of about 60 mm. Hg. 
The copper block was heated to 45° C., and the reaction product was formed in the top 
of the capillary tube. The section of the capillary containing the product was sealed 
off and the compound formed was identified by X-ray diffraction. 
first isotopes of the new actinide elements were obtained in very small 
amounts, and are very short lived. Specific and rapid methods are 
therefore necessary in identifying these elements, and ion exchange 
provides both. Much of the chemical knowledge we have of the 
actinide elements heavier than curium is concerned with their ion- 
exchange and elution properties. 
The trivalent actinide and lanthanide ions in aqueous solution 
undergo a cation exchange when a solid organic base-exchange poly- 
mer is stirred in. The solid material can then be placed at the top 
of a glass column filled with more of the organic polymer that is free 
of the actinides or lanthanides. Elution can then be accomplished by 
pouring through the column a solution containing ions that form 
complex ions with the actinide or lanthanide ions. In certain well- 
behaved systems the lanthanide elements elute from the column in the 
inverse order of their atomic numbers, that is, lutetium can be collected 
as the first element in the drops coming through the column, ytterbium 
as the second element, and so on to cerium. The whole process bears 
a close resemblance to chromatography. In the case of the actinides, 
the undiscovered element 103 will leave the column first, followed by 
element 102, and so on down the scale of atomic numbers. 
BERKELIUM AND CALIFORNIUM 
At the end of 1949 and beginning of 1950, experiments led to the 
production of elements 97 and 98, berkelium and californium. The 
first six transuranium elements were discovered almost in pairs, with 
time lapses corresponding to necessary improvements in technique and 
the accumulation of starting material. Milligram amounts of ameri- 
