【摘要】 <正> 式中k_s为盐析常数,c_s为盐的浓度,分别为非电解质和盐在无限稀释溶液中的偏摩尔体积,V_s为盐在液体状态下的摩尔体积,β_o为水的压缩系数,p_e为盐溶于水而产生的有效压力。此式推导过程中所用的极限条件为V_n→0,因此(1)式仅能用在极小的非电解质分子上,对于苯及苯的衍生物讲,K_s计算值约为实验值的2～3倍。当非电解质体积较大时,Mc-更多还原

【Abstract】 Some assumptions were made for the modified equation of the internal pressure theory originally suggested by McDevit and Long. When the distance between ion and nonelectrolyte molecule in aqueous salt solution is calculated, the ionic hydration should be considered for the larger nonelectrolyte molecules;and the nonelectrolyte molecule must be excluded from the primary solvation shell of the ion.For 1-1 electrolytes, we assume that: （a） Latimer’s radii are used instead of the radii of ions, i.e., r_L⁺=r_P⁺0.85 , r_L^-=r_P^-+0.10 , where r_P is the Pauling’s radius; （b） a in equation （1） is the average of the radii of cation and anion, i.e., a=1/2（r_L⁺r_L^-）; （c） b is the radius of the nonelectroiyte molecule, i.e., b=1/2（（V_n）/N）^1/3, in which V_n is the molar volume of the nonelectrolyte, N is the Avogadro’s number. In order to test these assumptions,it has been calculated for the salting-out constant of five benzene derivatives and four fatty acids in the solution of alkaline halides by the theories of （Ⅰ） Debye-McAulay, （Ⅱ） Conway-Desnoyers-Smith, （Ⅲ） McDevit-Long and （Ⅳ） modified McDevit-Long.For larger nonelectrolyte molecules equation （1） of the modified McDevit-Long theory （Ⅳ） gives results in better agreement with the experiment than those of （Ⅰ） , （Ⅱ） and （Ⅲ）更多还原