Clathrate formation in water-tetraalkyl ammonium iodide systems at high pressure

The phase diagrams of aqueous binary systems with PrBu₃NI(I), Bu₄NI(II), i-AmBu₃NI(III) and i-Am₄NI(IV) were studied at atmospheric and high pressures by DTA method. In systems III-H₂O and IV-H₂O at atmospheric pressure we observed polyhydrates melting incongruently at 7.1 and 14.7, correspondingly. In systems I-H₂O and II-H₂O hydrates form at higher pressure only, there are PrBu₃NI (15–25) H₂O at P0.13 kbar, Bu₄NI (25–35) H₂O at P0.4 kbar. In water systems with II–IV at pressure 1.2, 1.4 and 0.26 kbar correspondingly polyhydrates with smaller hydrate number form. Formation of hydrates in solution in the II-H₂O system does not occur at pressure greater than 7 kbar. The summarized P, T, X-phase diagram is discussed.