  We present an analysis of FLAMES-Giraffe spectra for several bright giants in
NGC 6441, to investigate the presence and extent of the Na-O anticorrelation in
this anomalous globular cluster. The field of NGC 6441 is very crowded, with
severe contamination by foreground (mainly bulge) field stars. Appropriate
membership criteria were devised to identify a group of 25 likely cluster
members among the about 130 stars observed. Combined with the UVES data
obtained with the same observations, high dispersion abundance analyses are now
available for a total of 30 stars in NGC 6441, 29 of them having data for both
O and Na. The spectra were analyzed by a standard line analysis procedure; care
was taken to minimize the impact of the differential interstellar reddening
throughout the cluster, and to extract reliable information from crowded, and
moderately high S/N (30-70), moderately high resolution (R ~ 23,000) spectra.
NGC 6441 is very metal-rich ([Fe/H]=$-0.34\pm 0.02\pm0.04$ dex). There is no
clear sign of star-to-star scatter in the Fe-peak elements. The alpha-elements
Mg, Si, Ca, and Ti are overabundant by rather large factors, suggesting that
the cluster formed from material enriched by massive core collapse SNe. The
O-Na anticorrelation is well defined, with about 1/4 of the stars being Na-rich
and O-poor. One of the stars is a Ba-rich and moderately C-rich star. The
distribution of [Na/O] ratios among RGB stars in NGC 6441 appears similar to
the distribution of colors of stars along the horizontal branch. The fraction
of Na-poor, O-rich stars found in NGC 6441 agrees well with that of stars on
the red horizontal branch of this cluster (in both cases about 80%), with a
sloping distribution toward lower values of [O/Na] (among RGB stars and bluer
colors (among HB stars).
