By measuring the radiant flux of the resonance lines of mercury, the field strength and the electron energy distribution function the influence of the current on the parameters, especially on the energy balance of the Hg-Ar positive column is investigated, compared with a kinetic model, iind interpreted. The decrease in yield of the 254 nm radiation with increasing current is linked to a corresponding increase of the losses due to elastic collisions with the rare gas atoms and is caused by the changes in the electron energy distribution function. Moreover, the influence of gas temperature, Hg-densities and effective life times is investigated.