1. & of H a I 5.110- 1 cm 3/sec I [271 A, ofNa 1 4.910." I cm 3/sec I
2. The theoreticalresults for electricalconductivity as a function of gastemperahlrearepresentedin Fig.1 fortheatomicconcentation n* = 0.25, where n* = 300PIT, From Fig.1 we find that the theoreticalcomputationunderestimatesthe electrical conductivityattemperaturehigherthan 1400"K ata lowertemperature range rhe.agreementwith the measuredvalues is good. According to Braun et al. the conductivity at the high tempnaturerange is enhancedhy ionizationof impurityamms from the wall ofthe furnace.In fact.we canshow that thetheorypredicls the conductivityat a high temperature.i.e. 1600'K,within 30% of the measuredvalues when 1ppm of chromium atoms, whose ionization potential is I eV, are included. Funhermore. the increaseof thedifferencebetween the theoreticaland experimental values as an increaseofthe temperaturecan be explainedby assumingthatamajormechanismfortheimpurityproductionisthe vaporization of the wall material.