The procedure above was first applied to document the effect of surface tension on bubble nucleation pressure in the rhyolite-H ₂ O system at P_SAT  = 200 MPa and T  = 800°C (Fig.  6 ).

Figure  6 shows that, for a constant value of P_SAT , the supersaturation pressure required for bubble nucleation, Δ P_N  =  P_SAT  −  P_N , increases dramatically with increasing surface tension: from 6.6 MPa at σ _LB  = 0.01 N/m ( P_N  = 193.4 MPa), to 66.1 MPa at σ _LB  = 0.05 N/m ( P_N  = 133.9 MPa), and to 179.6 MPa at σ _LB  = 0.1 N/m ( P_N  = 20.4 MPa).

In the calculations of Fig.  6 , we assumed that water behaved as a supercritical fluid (Eq.  12 ) and that N_D was equal to 1 mm ⁻³ .

In the case of an ideal gas behavior (Eq.  10 ), the calculated pressures are only slightly different from those in Fig.  6 : at σ _LB  = 0.1 N/m, for instance, $$ P_{\rm B}^* $$ and P_N are equal to 158.0 and 25.4 MPa if we use Eq.  10 , as compared to 153.0 and 20.4 MPa in the case of a supercritical fluid.