In contrast to the large body of work published on nonelectrolyte and strong electrolyte solutions, theoretical or correlational work is sparse for aqueous, volatile weak electrolytes. Van Krevelen's (1949) studies apply only to ammonia rich systems; further, they are limited to restricted ranges of ammonia/acid ratios and, for some cases, require experimental information which is not available. The more recent work of Edwards et al. (1975) is limited to low concentrations of weak electrolytes and to temperatures below (about) 80°C. The present work extends Edwards' earlier efforts to higher concentrations and higher temperatures.The purpose of this work is to extend a previously presented thermodynamic framework for calculating vaporliquid equilibria for solutions containing volatile weak electrolytes as commonly encountered in the chemical and related industries. The electrolytes examined are ammonia, carbon dioxide, hydrogen sulfide, and sulfur dioxide for the temperature range 0' to 17OOC; the composition range, depending on extent of ionization, may be as high as 10 to 20 moial. Limited information is also given for hydrogen cyanide.Parameters Al, Az, Aa, and A4 are given in Table 1. Parameters for the first and second dissociation constants of carbon dioxide are based on data reported by Clark ( 1966) ; for hydrogen sulfide, ammonia, hydrogen cyanide, and water, the parameters are those given by Tsonopoulos t In some cases it is preferable to write instead of Equation (2) -UNH&P -P w~) RT ~NH.@NE~$ = ~N H , Y O N + J~N H , exp ooo,(P -Pw') yco,@co,P = mco,y*co,Hco, exp RT yielding seventeen simultaneous, independent equations containing tho known partial pressures.
