%0 Journal Article %T Bulk Viscosity of Interacting Hadrons %A A. Wiranata %A M. Prakash %J Physics %D 2009 %I arXiv %R 10.1016/j.nuclphysa.2009.09.023 %X We show that first approximations to the bulk viscosity $\eta_v$ are expressible in terms of factors that depend on the sound speed $v_s$, the enthalpy, and the interaction (elastic and inelastic) cross section. The explicit dependence of $\eta_v$ on the factor $(\frac 13 - v_s^2)$ is demonstrated in the Chapman-Enskog approximation as well as the variational and relaxation time approaches. The interesting feature of bulk viscosity is that the dominant contributions at a given temperature arise from particles which are neither extremely nonrelativistic nor extremely relativistic. Numerical results for a model binary mixture are reported. %U http://arxiv.org/abs/0906.5592v2