In this paper, the liquid-liquid-solid triple-phase data of some aqueous two-phase systems (ATPSs) containing hydrophilic organic solvents (HOS) and simple salts were explored. The systems studied comprise aqueous solutions containing ethanol, 1-propanol, 2-propanol, or acetone with (NH4)(2)SO4 and solutions containing 1-propanol with (NH4)(2)SO4, NaCl, or KCl. The Gibbs phase rule predicts that there is a linear relationship existing at such a triple-phase boundary. The linear liquid-liquid-solid boundaries were determined, and the effects of temperature, solvent, and salt on the boundary were investigated. The tie line length (TLL) of the systems distributed on the triple-phase boundary was invariant. Phase equilibrium experiments determined that the average TLL of ethanol-(NH4)(2)SO4 ATPSs at 298.15 K was 62.93 % with a standard deviation of 2.13 %. The linear liquid-liquid-solid triple-phase boundary was used to elucidate the two-phase region and determine the content of organic solvent or salt in an unknown sample. These results increase our understanding of HOS-salt-water aqueous two phase system (ATPS) and will be useful for those looking to develop new systems for separation science.