盐类对双液系混溶性的影响

<正> (一)我们曾研究过一系列盐类对双液系混溶性的影响。希望在理论上和应用上有进一步的了解。本文继续对这一课题进行探讨。加盐于一定组成的双液系中,将改变液体内部分子间的相互关系,或增大其混溶性,使溶解度提高,或降低其混溶性,直至分层现象发生。这两种情况,均取决于双液

EFFECTS OF SALT ON THE MISCIBILTY FOR BINARY LIQUID SYSTEMS (Ⅰ)

The years before 1965 We had taken the investigation of the effects of salt on the miscibility for benzene-mthanol system. We discovered salts such as Nal, NaClO_4, NaSCN and NH_4I, which dissolve in methanol but sparingly soluble in benzene can turn the benzene-methanol system to a partial miscible one (a two phase system of three components). In addition, We found also that there exist a fair linear relation between the amount of salt added and the miscible temperature of the partial miscible system formed by adding the above salts to benzene-methanol mixture with a fixed molecular ratio. The upper end of such straight lines lies on the binodal curve developed by salt saturation, while the lower end lies on the intrinsic coexistance curve with tIe amount of salt equals to zero. The benzene-methanol system, when saturated with NaI, goes form complete miscibility to a partial miscible system with an upper critical solution temperature at 130.5℃, but when extrapolated by using the straight lines to zero amount of salt, the intrinsic coexistance curve obtained with U.C.S.T. within the region -60℃~-70℃. Recently, for comparison we recalculated the data of salts in cyclohexane-methanol system, which had studied early by Eckfeldt anh Lucasse in 1945. Not only the straight line relationship still present, but also the extrapolated no salt coexistance curve coinsides with the experimuta curve of this partial miscible system in ordinary pressure almost completely. According to Prigogine, the following gives the variation of the eritical solution temperature of a strictly regular solution caused by the addition of a third component. For the α's all are constants, thus this epuation represents the linear relation between temperature variation and the amount of the third oomponent being added. But, although this equation is in fact derived from the critical point of a strictly regular solution, there no reasons to consider it can not serve to any other points on the coexistance curve. Furthermore, verified by many experiments, this linear relationship can hold satisfactory for many common binary liquid solutions no matter what specil kinds the solution must belong. Therefore the above equation can be written as T=mXs+T_6 by rejecting the restrictions, where m is related to constants α_(AB), α_(AS) and α_B.