Report for General Research August 7 to October 30, 1950

Investigation of the physical and chemical properties of polonium important to its behavior and for the improvement of the quantity and quality produced is being continued. A sample of polonium is approximatelyf 1 x 10{sup 9} disintegrations per minute was counted in a Logac for 250 days in order to determine the half life. A statistical treatment of the results gave a half life of 138.3562 {+-} 0.446 days. Combined with previous calorimetric determinations a new grand mean of 138.3975 {+-} 0.0091 days resulted. The wavelengths of 138 lines appearing in the spark spectrum between 3050A and 3463A (Region 4) have been tentatively assigned to polonium and have a probable error of less than 0.02A. Thirty six lines in Region 6 (4225A to 5675A) tentatively assigned to polonium have a probable error of less than D D6A. A measurement of the resistivity of polonium has given a value of about 95 microohm centimeters, and although the Hall voltage could not be measured with much precision, it was possible to set a maximum value of 0.03 millivolt. These values indicate the polonium is a metallic conductor rather than a semiconductor. A rugged but compact gauge made of stainless steel with a tantalum diaphragm has been constructed to have a good sensitivity for the vapor pressure measurement of polonium tetrachloride. Studies by X-ray methods have shown that platinum nickel, and silver form compounds with polonium under the conditions of preparation, while tantalum, gold stainless steel, and beryllium do not. Bismuth formed an alloy of no definite composition which could be separated into its components at 485{sup o} Silver plonide decomposed at 559{sup o}