Birefringence of flow

Birefringence of Flow. In general, the birefringence of flow of aqueous pectin solutions behaves like the viscosity (24). 

It has been assumed so far that the behaviour of the molecules could be described with sufficient accuracy by the distance between the two ends. The fact that these ends are connected by a series of chain-elements was expressed by the introduction of the fictive force K [equation (11)]. The further development of the theory required some additional assumptions. We may mention, for instance, that the friction experienced in the motion of the two ends towards each other was assumed to be proportional to the total number N of statistical chain-elements, since on the average all these chain-elements will be involved. Further, a quantitative treatment of the birefringence of flow was only made possible by assuming that the molecules on the average retain their symmetry of rotation in the streaming liquid. 

Theoretical work in recent years has thrown some light on the relation between the birefringence of flow in solutions of long-chain molecules and the molecular weight of these substances. The subject has been treated in section 7 of Chapter IV, p. 115. The contribution of a particle with molecular weight Mi to the double refraction A is proportional to Mi (see equation 31 on p. 116), Thus, for the value of A /c we have an equation which is of the same form as (16), namely... 

The birefringence of flow in solutions of long-chain molecules was discussed in Section 7. Other optical methods for the determination of particle si e were mentioned in Volume I. One of them is the direct photographic observation in the electron microscope. By way of example we may mention the experiments with the rod-shaped molecules of tobacco-mosaic-virus Attempts to apply this method to the spherical molecules of glycogene, a polysacharide, were made by Htjsemann and Rtjska. ... 

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