documentclass[12pt]{book}
usepackage{tikz,pgfplots}
pgfplotsset{compat=1.3,width=10cm}
pgfkeys{/pgf/number format/.cd,set decimal separator={,}}
begin{document}
begin{tikzpicture}
begin{semilogxaxis}[grid=both,enlarge x limits=false,scale only axis,width=8.5cm,height=6cm,ymin=1,ymax=1.5,tick style={draw=none}]
addplot[color=black,mark=*,mark size=1pt]
coordinates{(0.666667,1.21982)(1.49206,1.19949)};
end{semilogxaxis}
end{tikzpicture}
end{document}