The problem of X Persei

X Per is a variable emission line star which shows among other peculiarities a weak X-ray emission (4U 0352+30) and a strongly variable IR excess (Ferrari-Toniolo et al. 1978, Viotti et al. 1980). A curve of growth for the UV interstellar lines of ionized species and of NI, OI, and the energy distribution of X Per in different epochs are presented. The UV spectrum of X Per shows broad asymmetric resonance lines belonging to a large ionization range (from SiII to CIV and probably NV) formed in the outer layers of the expanding envelope where large temperature differences seem to be present. (C.F.)