Figure 1.

Mixing pressure π_mix=π−π_elas−π_ion of polyacrylate gels vs gel volume fraction ϕ in salt solutions containing 40 mmol∕l NaCl plus various amounts of CaCl₂ at room temperature; data from Horkay and co-workers (Refs. ⁹, ²⁷). The curves show Eq. 2 fitted to the data; χ₀ and χ₁ are shown in Fig. 8.