The reduction of Pa2O5 with carbon has been investigated in the temperature range 1000-2200°C. As a first step at about 1100°C reduction of Pa2O5 to PaO2 occurs, followed by complete reduction to PaC at higher temperatures and reduced pressures. The CO-equilibrium pressures of the reaction: PaO2 + 3C = PaC + 2CO have been determined in the temperature range of 1290-1440°C. The temperature dependence is given by: log Pco = 12,07-19940/T (with Pco in torr). The PaC structure has been identified from X-ray powder patterns as being identical to those of the other actinide monocarbides (fcc structure, NaCl-type a0 = 5,0608 ± 0,0002 Å). At temperatures above 2000°C and with an excess of free carbon formation of a higher carbide, probably the dicarbide, PaC2 could be observed. © 1969.
