def bC_Mg_HSO4_RC99(T, P):
    """c-a: magnesium bisulfate [RC99]."""
    b0 = 0.40692
    b1 = 1.6466
    b2 = 0
    C0 = 0.024293
    C1 = -0.127194
    alph1 = 2
    alph2 = -9
    omega = 1
    valid = T == 298.15
    return b0, b1, b2, C0, C1, alph1, alph2, omega, valid
