The elemental abundances of symbiotic giants are essential to address the role of chemical composition in the evolution of symbiotic binaries , to map their parent population , and to trace their mass transfer history .
However , the number of symbiotic giants with fairly well determined photospheric composition is still insufficient for statistical analyses .
This is the third in a series of papers on the chemical composition of symbiotic giants determined from high resolution ( R \sim 50000 ) , near-infrared spectra .
Here we present results for 24 S-type systems .
Spectrum synthesis methods employing standard local thermal equilibrium analysis and atmosphere models were used to obtain photospheric abundances of CNO and elements around the iron peak ( Fe , Ti , Ni , and Sc ) .
Our analysis reveals metallicities distributed in a wide range from slightly supersolar ( [ Fe / H ] \sim + 0.35 dex ) to significantly subsolar ( [ Fe / H ] \sim - 0.8 dex ) but principally with near-solar and slightly subsolar metallicity ( [ Fe / H ] \sim - 0.4 to -0.3 dex ) .
The enrichment in ^ { 14 } N isotope , found in all these objects , indicates that the giants have experienced the first dredge-up .
This was confirmed in a number of objects by the low ^ { 12 } C/ ^ { 13 } C ratio ( 5–23 ) .
We found that the relative abundance of [ Ti/Fe ] is generally large in red symbiotic systems .