Fig. 4. Extended Hill plots (where Y is the fractional O₂ saturation) of S. parasitica Hb at pH 7.04-7.06 and either 5°C (triangles) or 25°C (circles) and at pH 7.63 and 25°C (squares). The intercepts of the asymptotes to the lower parts of the curves (broken lines with slopes of unity) with the vertical axis at logP_O indicate the K_T (the O₂ association constant of the low-affinity deoxy state of the molecules) values. Heme concentration, 0.80 mmol l^-1. (7.50 Torr=1 kPa.)