Context : NGC 6522 has been the first metal-poor globular cluster identified in the bulge by W. Baade .
Despite its importance , very few high resolution abundance analyses of stars in this cluster are available in the literature .
The bulge metal-poor clusters may be important tracers of the early chemical enrichment of the Galaxy .

Aims : The main purpose of this study is the determination of metallicity and elemental ratios in individual stars of NGC 6522 .

Methods : High resolution spectra of 8 giants of the bulge globular cluster NGC 6522 were obtained at the 8m VLT UT2-Kueyen telescope with the FLAMES+GIRAFFE spectrograph .
Multiband V,I,J,K _ { s } photometry was used to derive effective temperatures as reference values .
Spectroscopic parameters are derived from Fe I and Fe II lines , and adopted for the derivation of abundance ratios .

Results : The present analysis provides a metallicity [ Fe/H ] = -1.0 \pm 0.2 .
The \alpha -elements Oxygen , Magnesium and Silicon show [ O/Fe ] =+0.4 \pm 0.3 , [ Mg/Fe ] = [ Si/Fe ] = +0.25 \pm 0.15 , whereas Calcium and Titanium show shallower ratios of [ Ca/Fe ] = [ Ti/Fe ] =+0.15 \pm 0.15 .
The neutron-capture r-process element Europium appears to be overabundant by [ Eu/Fe ] =+0.4 \pm 0.4 .
The neutron-capture s-elements La and Ba are enhanced by [ La/Fe ] =+0.35 \pm 0.2 and [ Ba/Fe ] =+0.5 \pm 0.5 .
The large internal errors , indicating the large star-to-star variation in the Ba and Eu abundances , are also discussed .

Conclusions : The moderate metallicity combined to a blue Horizontal Branch ( BHB ) , are characteristics similar to those of HP 1 and NGC 6558 , pointing to a population of very old globular clusters in the Galactic bulge .
Also , the abundance ratios in NGC 6522 resemble those in HP 1 and NGC 6558 .
The ultimate conclusion is that the bulge is old , and went through an early prompt chemical enrichment .