How correct is the EOS of weakly nonideal hydrogen plasmas?

Helioseismology opens new possibility to check EOS of weakly nonideal hydrogen plasmas with high precision, using reconstructed local sound velocities within 10-4 accuracy. A comparison of different theoretical models with experiment permits to verify the existing methods of calculation bound states and continuum contribution to the second virial coefficient within the framework of physical nature. The regular way of the deduction expression for EOS is presented and generalization of the EOS for broad atomic states and two temperature non-equilibrium case is proposed. (copyright 2003 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)