The Thermionic Emission from Clean Platinum

The thermionic emission from thoroughly outgassed platinum in high vacuum has been measured to one-half percent over the temperature range 1360 to 1750^∘{}K, the temperatures being measured by careful optical pyrometry. The values obtained for the thermionic constants of the T² law are, when corrected for the Schottky effect, b=72, 820^∘K, φ=6.27 volts, $A=17,000$ amp/cm² deg². The value of φ is possibly in error by not more than 1 percent because of uncertainties in the temperature scale, and agrees within one-half percent with the value of the photoelectric work function previously obtained. The data confirm the previous announcement that for clean platinum A is 250 times greater than the theoretical value of 60.2 amp/cm² deg².