Add to ORKGThe electron temperature T/sub e/ is obtained from five optically non-thin Ar I line-transitions. It is possible to measure T/sub e/ without any knowledge of transition probabilities. The electron density N/sub e/ can be calculated from measured excited level densities using the partial LTE model. It appears that there is a functional dependence of N/sub e/ on T/sub e/, suggesting that transport processes are of only minor importance. The deviations from LTE can be described by assuming a N/sub e/-dependent overpopulation of the ground level of Ar I. This overpopulation factor varies from 1.9 for N/sub e/=2*10/sup 16/ cm/sup -3/ to 1.25 for N/sub e/=2*10/sup 17/ cm/sup -3