Analytical and Miscellaneous Applications of Refractivity

In general the refractive indices of mixtures of non-interacting components plot smoothly against the proportions present the same is true of specific or molecular refractions. Equations (3) and (4)—when Ri and i 2, or r1 and r2, are known—obviously make possible the estimation of a concentration w2 or f2 by measurement of n12 and dl2 (since 

Specific refractivity increments, (n12 — %i)/c, where c is in grams per cm3, are independent of c with aqueous solutions of proteins and many water-soluble macromolecules of natural or artificial origin (Oster, 1955) they—and dnjdc also—are best recorded by differential refracto-meters (such as that designed by Debye, 1946) and are necessary quantities in the determination of particle weights from light-scattering data. 

Tests showed that M s secured via (17) were as accurate as others determined cryoscopically. The method is obviously generally applicable to all liquid polymers for which the structural pattern is known and is uniformly repeated throughout the macro-chain as x becomes larger the observable differences between the L s and d s of molecules with x and x +1 become smaller, and precision in M is thereby reduced. An analogous proposal by Farquharson (1936) to use Pascal s constants 

In fact, of course, the electric vector in a light beam is not steady but varies sinusoidally with time, so that the intensity E must be amended to E0 cos 277-vt (where v is the frequency of the light and t the time) the electron imagined above will therefore be executing forced vibrations. By arguments set out by Lorentz (1909) and explained in detail by Partington (1953), the general equation (19) is reached 

This displays the facts that the field inside a dielectric is not simply that which is applied externally (but is modified by intervening polarized molecules), and that the medium may contain k kinds of oscillators each with its own proper frequency v0. In the case of a single oscillator, the same in all the N molecules per gram-molecule, and when v2 is negligible compared with i, we have (20), from (18) and (19)  

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