Zoo ANNUAL REPORT SMITHSONIAN INSTITUTION, 1959 
centrations in solution, and with the development of balances of the 
required sensitivity, micrograms were also sufficient for gravimetric 
analysis. Liquid volumes in the range 107 to 10° ml. were meas- 
ured with an error of less than 1 percent by means of finely calibrated 
capillary tubing, the movement of liquid being controlled by air pres- 
sure. Smaller pipettes were constructed to fill by capillary action. 
Chemical glassware, such as test tubes and beakers, was constructed 
from capillary tubing having an internal diameter of 0.1-1 mm. and 
was handled with micromanipulators. The weights of solid reagents 
and precipitates handled in ultramicrochemical work are usually in 
the range of 0.1-100ug. There are some changes in method in- 
volved in the change of scale—thus, solids are usually separated from 
liquids by centrifuging rather than by filtration. The actual chemical 
work is usually done on the mechanical stage of a microscope, where 
the essential apparatus is within view (fig. 2). Among the early 
accomplishments in ultramicrochemistry was the isolation of pure 
neptunium (pl. 1, fig. 1) and pure plutonium compounds (pl. 1, fig. 2) 
as well as the preparation of plutonium metal. Figures 1 and 3 show 
schematic drawings of the experimental arrangements used in the 
preparation of pure plutonium metal and pure plutonium trichloride. 
Plutonium is the only synthetic element that has been produced and 
isolated in kilogram quantities. The large plant at Hanford, Wash., 
was constructed on the basis of investigations performed with about 
2 mg. of plutonium; the scaleup between ultramicrochemical experi- 
ments to the final Hanford plant corresponds to a factor of about 
10°, surely a scaleup of unique proportions. 
Frequently chemical investigation of plutonium and of other trans- 
uranium elements is carried out on a scale of a milligram or less by 
choice, rather from any limitation on supply—Pu*® is exceedingly 
toxic because of its high alpha-radioactivity, amounting to about 
THORIA CAP 
TUNGSTEN HEATING COIL 
THORIA OUTER CRUCIBLE 
THORIA INNER CRUCIBLE 
VACUUM LINE <—— 
BARIUM METAL 
LOOSE FITTING 
THORIA PLATE 
PLUTONIUM TETRAFLUORIDE 
ROUND JOINT 
Ficure 1.—Apparatus used in the first preparation of plutonium metal (November 1943). 
35 wg of plutonium tetrafluoride was treated with volatilized barium metal in a thoria 
crucible at 1400° C. The metallic plutonium was produced as silvery globules weighing 
about 3 wg each. 
