ISSN:
1573-1111
Keywords:
High pressure
;
clathrate formation
;
clathrate hydrate
;
phase diagrams
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract P,T,X phase diagrams of the CH2Cl2-H2O, the CHCl3-H2O and the CCl4-H2) systems have been studied by DTA in the pressure range 10−3 to 5.0 kbar. Under pressure the cubic structure II (CS-II) hydrates forming in all the systems are replaced by hydrates with the composition M·7.3 H2O whose stoichiometry and positive dT/dP values of melting lead us to believe that they are CS-I hydrates. In the CH2Cl2 and CHCl3 systems the nonvariant point coordinates of the hydrate transformationQ 2 h (l1h17h7l2, where l1 and l2 are liquid phases abundant in water and hydrate former, respectively, h17 and h7 are hydrates with hydrate numbers 17 and 7, respectively) areP = 0.6 kbar, T = −1.5°C andP =2.65 kbar,T = −10.5°C, respectively. In the CCl4 system the 4-phaseQ 3 h point (l1h17h7s, where ‘s’ is crystalline CCl4) has coordinatesP = 0.75 kbar and T = 0.4°C. The main obstacle of the present study, the very slow achievement of equilibrium, has been eliminated by adding small amounts (0.25% by mass) of surfactants followed by ultrasonic mixing. We have shown that this accelerates the achievement of equilibrium without changing its position.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01133502
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