Pavlov et al.¹ determined the mutual solubilities of acetonitrile and butane between 276 and 335 K for unknown pressure by the synthetic method and these data were presented in graphical form only. Gruszkiewicz et al.² measured the mutual solubilities of (1) and (2) between 298 and 334 K and pressure 5 to 10 MPa using the synthetic method and reported their results only in the form of an equation. Warowny³ studied the phase equilibrium of the liquid-liquid-gas system and the mutual solubility of (1) and (2) between 319 and 336 K and over the pressure range 0.45 to 0.68 MPa by the synthetic method.

The upper critical solution temperature has been reported as 333.59 K² (at 5 MPa), 335.2 K¹ (for unknown pressure) and 336.22 K³ (at 0.68 MPa). The data^1-3 are in reasonable agreement and thus their average value: UCST = 335.7 ±0.5 K is recommended. The corresponding critical solution composition has been reported in as x_cl = 0.4753² (at 5 MPa), x_cl = 0.478¹ (for unknown pressure) and x_cl = 0.571³ (at 0.68 MPa).
All experimental values reported^1,3 have been approximated by an equation based on the scaling law (described in the introduction to this volume) for which the following parameters have been derived:

(mean standard error of estimate was 0.0262).
For approximation x_cl and UCST determined by Pavlov et al.¹ have been used. In the opinion of the evaluator, the mutual solubilities calculated by this equation may be treated as tentative. The results of calculations for the selected temperatures are presented in the following table. This relationship, together with experimental points reported by Pavlov et al.¹ and Warowny,³ are also presented in Fig. 4.