CLAUDE JAMBON and CESEVIEVE DELMAS. Can. J. Chem. 55, 1360 (i977). Solution viscosities have been measured at 25 'C on seven 1 systems of SnR, compounds: SnBut, with SnMe,, SnEt,, SnPr,, SnOct,, SnLaur, and SnLaur, with SnEt, and SnPr,. The efTect of shape difference on excess solution viscosities was investigated. The experimental value A In q,,, = In q, -xl In q l -x, In q 2 was compared to A 11: l l t h A In lit, was obtained using AGz,(niixing) in place of GM'(activation) and free volume theories. Experimental heats of mixing have been measured and are used in A In q t h It was found that with the Van der Waals model for the energy, the difference A In qc,, -A In qth, indicative of the agreement between the predicted and experimental value, is relatively small for mixtures of molecules not having a large size difference. However, for systems different in size, A In q,,, -A In q t h is positive and large and is shown to be an increasing function of the size difference. A In q,, could be adjusted to A In q... by adding a term 111 I~~, T . = C(V,*"~ -V2*112)2 where V* is the core volume. To confirm the validity of In q,,,, the seven I1 systems chosen in order to present a large range (Vl*'lZ -V2*liZj were measured: SnBut, + squalane, Si(OEt), + Si(OOct),, Si(OEt), + Si(OOct),, n-C, + Si(OOct),, Si(OEt), + squalane, n-Clz + SnOct,, Si(OMe), + Si(OOct),, n-C16 + benzene. Une valeur de c de 5.3 x cm3 semble convenir approximativement pour les systems prksentes ici. L'effet de condensation de SnEt, et SnPr,, observe par calorimetric, peut sans doute se voir sur la sCrie, SnLaur, avec SnEt,, SnPr,, SnBut,.
