Polysulfides phase equilibrium

Final comment. Complete thermodynamic and kinetic studies have been made to identify new individual polysulfide phases. The static membrane gauge method appears to be the most promising for controlling the equilibrium state in the systems. This method is also the main source in constructing Ps T-x equilibrium diagrams, which provide valuable data for crystal-growth processes of the intermediate polysulfides. 

The thiosulfate by-product does not take part in the subsequent reactions with the organic chlorides. The x value in equation (160) is referred to as the rank of the sodium polysulfide a typical value for x is 2.25. However, since aqueous sodium polysulfide is a complex mixture containing various polysulfide anions in equilibrium, the final polymer obtained in equation (158) may contain various structural units -S - (n = 1 -4). In addition, the aqueous phase contains OH , resulting in some terminal OH groups in the polymer. By applying an excess of sodium polysulfide (1.3 mol per mol RCL), the number of chain-terminating OH groups is reduced (see equation 161). 

State instead of equilibrium one. As a result, the equilibrium phase diagram with two individual poly sulfides is modified to that witli one nonstoichiometric phase, see fig, 3. Therefore, the method of automatically monitoring the weight change with low sensitivity is not suitable for studying phase equilibria in polysulfides systems. 

The solidus portion of the pressure-dependent equilibrium phase diagram of the PrS2,o-PrSi,5 system constructed by methods (a) and (b) is shown in fig. 4. A series of new sulfur-deficient polysulfides, PrSi.9oo(2), PrSi.846(6)i PrSi 756(8), and PrSi.702(7), in addition to tlie strict stoichiometric PrS2 has been found, separated by miscibility gaps. The intermediate polysulfides are seen to have narrow fields of stability. Therefore, it is difficult to prepare a single-phase intermediate polysulfide, especially when the desired thermodynamic parameters are unknown. On the other hand, the information resulting from these diagrams on the nonstoichiometric polysulfide compositions opens... 

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