The Mechanism of Chromatographic Retention - The Association of Methanol with Water > Page 36

Thus, if (ni) is the refractive index of a mixture and (vi) is the equivalent molar volume of the mixture,

Now, (24)

Substituting for (vi) from (41), for (XM), (XW) and (XMW) from (20), (21) and (22); and simplifying,

(25)

Thus, (26)

Accepting published values for the molar refractivities of water and methanol, and assuming a range of values for the equilibrium constant (k) and the refractive index (ni) of the methanol/water associate, the actual values that fit the equation for these two parameters can be identified, using a simple iterative program that compares the calculated values for (ni) to those experimentally determined.