Solubilities in the system comprising nitromethane and octadecanoic acid have been reported in three publications. Broughton and Jones,¹ at 387 K, and Hoerr, et al.,² between 293 and 369 K, studied the mutual solubilities of (1) and (2) using the synthetic method. Schmid et al.³ determined the upper critical solution temperature also by the synthetic method.

At the UCST, the only temperature where direct comparison is possible, the two results available are in only fair agreement: Schmid et al.³ (386.7 K) and Broughton and Jones¹ (387.2 K). Accordingly, in the absence of confirmatory studies, all data must be regarded as tentative. However, it may be noted that the UCST values of Schmid et al.³ in well characterized systems are generally lower than other reports and thus the value from Broughton and Jones¹ is probably more realistic.

The measured UCST is not consistent with the values calculated from the respective relationships in the nitromethane - alcohol series, discussed at the beginning of this volume (the calculated value, UCST = 386.5 K ). The numeric values of liquid-liquid solubility, reported in Broughton and Jones¹ and Hoerr, et al.,² have been approximated by the equation based on scaling law (described in the introduction material to this volume "Relations of Solubility Data in Binary Systems Containing Nitromethane") and the following parameters have been adjusted:

a₁ = 0.34023, a₂ = 0.50866, b₁ = -1.00084, b₂ = -0.03378

(mean standard error of estimate was 0.0754).

As an approximation, the UCST = 387.2 (Ref. 1) and x_c1 = 0.86 have been used. This relationship together with all experimental points from liquid-liquid region^1,2 are presented in Fig. 38 . The calculated results for the selected temperatures are presented in the following table. These mutual solubilities may to be treated as tentative.