Low Energy Parameters of the KK and Pipi Scalar-Isoscalar Interactions

Threshold expansions of the $\pi\pi$ and $K\overline{K}$ spin 0 and isospin 0 scattering amplitudes are performed. Scattering lengths, effective ranges and so--called volume parameters are evaluated. Good agreement with the existing experimental data for the $\pi\pi$ scalar--isoscalar amplitude is found. An importance of future accurate measurements of the $K\overline{K}$ threshold parameters is stressed. New data are needed to understand the basic features of the scalar mesons.