Phase equilibria in the thiourea-chloroform and thiourea-carbon tetrachloride systems

Phase equilibria in the thiourea-chloroform and thiourea-carbon tetrachloride binary systems with clathrate formation were studied by the physicochemical analysis methods over the temperature range 200-450 K. The regions of the existence of the inclusion compounds 2.3(NH 2 ) 2 CS.CHCl 3 , 2.9(NH 2 ) 2 CS.CCl 4 , and 3.0(NH 2 ) 2 CS.CCl 4 were determined. These compounds decomposed incongruently at 345.9, 399.2, and 411.4 K, respectively, to produce rhombic thiourea and the guest component. The unit cell parameters of the clathrate phases were found to be (in hexagonal axes) a = 15.84 A, b = 12.65 A (guest CHCl 3 ) and a = 15.71 A, b = 12.46 A (guest CCl 4 ). The number of clathrate phases and their stoichiometry and relative stability are discussed in terms of the orientation of guest molecules in rhombohedral thiourea channels. Chloroform is characterized by one type of packing in matrix channels, whereas at least two predominant packing types are observed for carbon tetrachloride.