  It is very likely that most (perhaps all) Galactic globular clusters (GGCs)
have experienced two or even more star-formation episodes. This is indicated,
in particular, by peculiar chemical composition of the cluster stars which show
large variation in the abundances of light elements, such as Li, C, N, O, Na,
Mg, and Al. We studied the abundances of Na, Mg, and Al in the atmospheres of
103 red giant branch stars located below (49 stars) and above (54 stars) the
RGB bump in the GGC 47 Tuc. Our results show that the spread of [Na/Fe]
abundance ratios is about three times larger than that of [Mg/Fe]. Our data
also confirm the existence of weak Na-Al correlation, similar to the one
observed in other GGCs. At the same time, we find no evidence for the existence
of three populations of stars characterized with different abundances of
aluminum, as reported recently by Carretta et al. (2013).
