TRANSURANIUM ELEMENTS—SEABORG 253 
BINOCULAR 
STEREOSCOPIC 
MICROSCOPE 
GIVING Ca. 30x 
MAGNIFICATION 
1/2 ml SYRINGE 
SIMPLE MIGROPIPET DOWN 
MICROMANIPULATOR TO 0.1 MICROLITER 
PER Cm.OF LENGTH 
MICROSCOPIC FIELD 
Ficure 2.—Experimental arrangement for the study of precipitation reactions on the micro- 
gram scale. 
140 million alpha-disintegrations per minute per milligram; special 
equipment and precautions, as well as the use of material in very 
small amounts, are necessary when working with it. 
AMERICIUM AND CURIUM 
After plutonium had been produced in quantity, the discoveries of 
americium (1944-45) and curium (1944) were made, The speed of 
discovery of these elements was due largely to the accurate prediction 
of their chemical properties on the basis of their assumed position in 
the periodic table (p. 249). Curium, discovered by R. A. James, L. O. 
Morgan, A. Ghiorso, and the author, was synthesized as Cm?” by the 
bombardment of plutonium with helium ions. The production of 
americium by James, Ghiorso, and the author was accomplished by 
preparing Pu**, which decays by beta emission to Am, 
IDENTIFICATION BY ION EXCHANGE 
The ion-exchange technique, coupled with element-by-element com- 
parison of the behavior of corresponding actinide and lanthanide 
elements, has been essential in the discovery of the transuranium 
elements. Since the actinide elements above plutonium are predom- 
inantly trivalent in solution and have a close chemical resemblance, 
most conventional chemical separations are not suitable. Again, the 
