Electrotransport of carbon in molybdenum and uranium

The electrotransport velocity of carbon in molybdenum and uranium was measured over a temperature range slightly below their melting points. Carbon was found to have a positive effective valence of 2.26 to 1.74 in molybdenum over the temperature range of 1890 to 2320°C and a negative value of - 5.0 in γ-uranium between 850 and 1000°C. The effective valences of nitrogen and oxygen were also observed to be positive in molybdenum and negative in uranium but their magnitudes were not determined. The diffusion coefficients for carbon in both metals were determined over the same temperature ranges.¹⁴Carbon was used as a tracer in the molybdenum work. The diffusion coefficient for carbon in molybdenum is described by the equationD = D ₀ exp (-†H/RT) whereD ₀ and †H are 0.033 cm²/s and 153 kJ/mole (36.60 kcal/mole), respectively. The values forD ₀ and †H for carbon in γ-uranium were determined as 0.218 cm₂/s and 123 kJ/mole (29.40 kcal/mole), respectively. Electrotransport was shown to be an effective method of purifying a small amount of each metal with regard to carbon as indicated by resistance ratio measurements and chemical analysis. A correlation is also presented showing the relationship between the atomic size of the solvent metal and the sign of the effective charge of the migrating solute.