The liquid-liquid equilibrium of water and 1-octanol has been rigorously studied by Chen and Siepmann using Monte Carlo simulations with advanced sampling techniques. In both pure and water-saturated 1-octanol, microscale heterogeneities exist consisting of polar and non-polar domains. In water-saturated 1-octanol, it was shown that considerably more large hydrogen bond aggregates (i.e., polar domains) exist, where a hydrogen bond aggregate is defined as a collection of molecules where every molecule shares at least one hydrogen bond with another molecule belonging to the same aggregate. For water-saturated 1-octanol, approximately 50% of the water and 1-octanol molecules belong to clusters with aggregation numbers greater than 25; this is approximately double that in pure 1-octanol. Additionally, Chen and Siepmann rigorously computed the mutual solubility of water and 1-octanol and found that the results were highly sensitive to the force fields used. They found that their combination of TIP4P water and TraPPE-UA 1-octanol resulted in an equilibrium concentration of 0.21 mole fracs of water in the octanol rich-phase in good agreement with experiment. In earlier studies, it was found that a combination of TIP4P water and OPLS-UA 1-octanol resulted in an equilibrium concentration of 0.09 mole fracs , and SPC water with a the modified GROMOS96 force field for 1-octanol resulted in an equilibrium concentration of 0.16 mole fracs .