EXCESS VOLUMES IN (N,N-DIMETHYLFORMAMIDE PLUS METHANOL PLUS WATER) AT THE TEMPERATURE 313.15 K

Excess molar volumes V-m(E), measured at the temperature 313.15 K in a dilution dilatometer are reported for {xCH(3)OH + (1 - x)H2O}, {xHCON(CH3)(2) + (1 - x)CH3OH}, and {x(1)HCON(CH3)(2) + x(2)CH(3)OH + (1 - x(1) - x(2))H2O}. The results have been analysed using various correlation equations and the possibility of predicting the ternary V-m(E) values from the binary ones is examined. The binary V(m)(E)s for {xHCON(CH3)(2) + (1 - x)(H2O or ROH)}, where ROH is CH3OH or C2H5OH or CH3CH2CH2OH, have been interpreted by dividing this quantity into two terms: V-m(E) = (V-m, assoc(E) + V-m, size(E)), which depend on effects connected with association (V-m,assoc(E), and effects arising from differences in molecular sizes (V-m, size(E)). The second term, V-m, size(E), has been calculated using Flory's equation of state, giving the possibility of estimation of the V-m, assoc(E) values. This allows ordering of the water and the alcohols according to their interaction strength with the N,N-dimethylformamide molecule as follows: water > methanol > ethanol > propan-1-ol.