Spectra of four selected lines (CI 5380.3 Å, MnI 5394.7 Å, FeI 5930.2 Å and SiI 5948.5 Å) have been obtained in the quiet photosphere, at regular intervals along the polar axis and the equator. The spatially averaged spectra have been analysed, studying the centre-to-limb variation and possible changes with heliographic latitude of the residual intensity equivalent width, full width at half line minimum and bisector of the lines.