Rotations of the dispersed

FIGURE 8.4 Rotation of the dispersing element directs different wavelengths to emerge from the exit slit. 

The bottom of the mixing zone contains stationary vanes attached to the bottom of the contactor housing. These vanes stop the rotation of the dispersion that is created in the annular gap and allows the dispersion to flow under the rotor. The opening into the rotor is located at the center of the bottom surface of the rotor. If the bottom vanes were not there, the dispersion would back up in the annular mixing zone and flow out via the lower collector ring. If this happened, a breaking dispersion would flow out the less-dense-phase exit port. 

The presence of a prism in the spectrophotometer causes the light to be dispersed into a rainbo v. At the exit slit, the different colors of visible light are intense as each arrives at a separate point in the exit slit plane in this way a series of images of the entrance slit becomes focused on the plane. Rotation of the dispersion element then causes the band of colors to move relative to the exit slit, so that the desired entrance slit image becomes centered on the exit slit (Horiba http //www.horiba.com/us/en/scientific/products/optics-tutorial/monochroma-tors-spectrographs/ c375 2). 

We see that the viscosity increase in suspensions can be calculated from energy dissipation effects related to the rotations of the dispersed particles and the tractions which arise over their surfaces. The surface velocity of the sphere is... 

As an approximate rule, break-up of droplets occurs for a Weber number in excess of one, a rule of thumb that is actually valid for the range of viscosity ratios of the dispersed phase to the continuous phase of less than approximately five. Higher viscosities of the disperse phase lead to serious difficulties with emulsification because the shear energy is then dispersed in rotation of the droplets. 

In some cases there is evidence of multiple solid-solid transitions, either crystal-crystal polymorphism (seen for Cl salts [20]) or, more often, formation of plastic crystal phases - indicated by solid-solid transitions that consume a large fraction of the enthalpy of melting [21], which also results in low-energy melting transitions. The overall enthalpy of the salt can be dispersed into a large number of fluxional modes (vibration and rotation) of the organic cation, rather than into enthalpy of fusion. Thus, energetically, crystallization is often not overly favored. 

Optical activity comes from the different refractions of right and left circularly polarized light by chiral molecules. The difference in refractive indices in a dissymmetric medium corresponds to the slowing down of one beam in relation to the other. This can cause a rotation of the plane of polarization or optical rotation. The value of specific rotation varies with wavelength of the incident polarized light. This is called optical rotatory dispersion (ORD). 

Let us consider two points F and G between which the local reciprocal lattice varies from g to + rfg. If the deformation is small the shape of the dispersion surface does not change and only a displacement of the hyperbolae results. We can consider this as a rotation about the origin of reciprocal space,... 

Figure 8.10 Rotation of the local reciprocal lattice vector in a distorted crystal, giving rise to a displacement of the dispersion surface hyperbola...

A large proportion of spectral data is acquired by dispersive spectrophotometry. The discussion that follows is restricted to instruments that use a diffraction grating as the principal dispersive element. The sense of the following also applies to systems that use a prism. In general, we treat systems using photosensitive detectors and fixed-position slits. Scanning is achieved by rotation of the diffraction grating. 

The rotational diffusion coefficient Dr of a rodlike polymer in isotropic solutions can be measured by electric, flow, and magnetic birefringence, dynamic light scattering, and dielectric dispersion. However, if the polymer has some flexibility, its internal motion makes it difficult to extract Dr for the end-over-end rotation of the chain from data of these measurements. In other words, Dr can be measured only for nearly rodlike polymers. 

Some time ago we measured the dielectric dispersion of a plant virus particle and found a critical frequency in the kHz region, therefore in a region that may well correspond to the eventual maximum of your ultrasonic absorption. We were able to describe the mechanism leading to this dispersion in terms of the rotation of the complete virus particle and of the motion of associated (or bound) counterions on the elongated surface of the particle. 

Rotation of the polarization plane (or the axes of the dichroic ellipse) by a small angle a occurs when the phases for the two circular components become different, which requires a difference in the refractive index n (Pearlman and Nguyen 1991). This effect is called circular birefringence. The change of optical rotation with wavelength is called optical rotary dispersion (ORD). 

Since the optical purity of the starting materials and the molar rotations of the pure optically active products are unknown, it is not possible to assay any partial racemization. In most instances the molar rotation of the products is as large as or larger than the starting material. It is probable that no racemization took place in these reactions, but it is impossible to state this unequivocally without a knowledge of the relationship between the rotatory dispersion curves and visible spectra of the products and starting materials. 

Reinkober studied the reflexion spectra for ultra-red rays. According to J. H. Gladstone and W. H. Perkin,12 the molecular refraction, dispersion, and magnetic rotation of the ammonium halides are ... 

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