Extensive calculations of the radiative emission of an atmospheric pressure hydrogen arc in the temperature range from 8000 to 15000 K have been undertaken, which show that a partly ionized hydrogen arc plasma may serve as an intense and accurate spectral radiation standard in the ultraviolet. The principal features of the spectrum are: Between 1215 Å and 3600 Å the hydrogen arc emits only continuous radiation, dominated by the Balmer recombination continuum. Between 1215 Å and 930 Å the lower members of the Lyman series appear strongly Stark-broadened and optically thick in their central parts. The higher Lyman lines merge into a quasi-continuum, which leads into the very strong Lyman continuum. Between 930 and about 400 Å the continuum is optically thick, i.e., it represents blackbody radiation at typical arc temperatures of 12000 to 15000 K.