The Angle of Deviation Method

Since the original model of Tiselius there have been many papers published that describe different methods of refractive index monitoring. From these publications, four general methods emerge for measuring refractive index the angle of deviation method, the critical angle method, the Fresnel method and the Christiansen method. The theory behind each of these methods will now be discussed. 

When a monochromatic ray of light passes from one isotropic medium. A, into another, B, it changes its wave velocity and direction. The change in direction is called refraction and the relationship between the angle of incidence and the angle of refraction is expressed in Snell s law of refraction 

Refractive index is a dimensionless constant that normally decreases with increasing temperature values given in the literature are usually measured at ambient temperature using the mean value for the two sodium lines. The refractive indices of some common solvents used as a mobile f iase are given in the Table of Physical Properties of Different Solvents given in the Appendix. 

The location of the focused beam rather than its intensity is determined by the angle of deflection resulting from the difference in refractive index between the two peurts of the ceU. As the beam changes location on the photocell, an output signal is 

When a ray of light passes from a medium of low refractive index to one of high refractive index, the refracted ray is bent away from the normal in the second medium. If the angle of the incident ray is increased, the angle of the refracted ray increases until the refracted ray is parallel to the boundary 

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The modem refractive index detector is the result of considerable research initiated by Zaukelies and Frost [2] and Vandenheuval and Sipas [3] and is now continued largely by the research and development laboratories of the major instmment companies. A diagram of a simple refractive index detector that is based on the angle of deviation method measurement is shown in figure 1. 

The Refractive Index Detector Based on the Angle of Deviation Method of Measurement Courtesy of the Millipore Corporation... 

Having compared these data with the geometry of the molecules calculated by the molecular mechanics method, the same authors concluded that in XXXVIIIc optimal orientation is achieved of the nucleo philic group OH with respect to carbonyl, namely, the angle of approach of 98°, while even insignificant deviations ( 10°) from it appreciably inhibit the reaction. The requirement for such refined adjustment of the reaction site became known as the orbital steering concept provoking lively discussion [118,119]. 

Perhaps the best discussions of the experimental aspects of the capillary rise method are still those given by Richards and Carver [20] and Harkins and Brown [21]. For the most accurate work, it is necessary that the liquid wet the wall of the capillary so that there be no uncertainty as to the contact angle. Because of its transparency and because it is wet by most liquids, a glass capillary is most commonly used. The glass must be very clean, and even so it is wise to use a receding meniscus. The capillary must be accurately vertical, of accurately known and uniform radius, and should not deviate from circularity in cross section by more than a few percent. 

Walk (of hole) The tendency of a wellbore to deviate in the horizontal plane. Wellbore survey calculation methods Refers to the mathematical methods and assumptions used in reconstructing the path of the wellbore and in generating the space curve path of the wellbore from inclination and direction angle measurements taken along the wellbore. These measurements are obtained from gyroscopic or magnetic instruments of either the single-shot or multishot type. 

In Fig. 2.9 the theory is compared with some experimental data. In these coordinates the Hubbard relation corresponds to a horizontal straight line with intercept 1/6, but for any finite xj deviations from 1/6 are observed. The angle formed by the straight lines with y=0 and y= defines the acceptable range of slopes. If experimental points are within the angle, the impact description may turn out to be acceptable. The above method for testing experimental data is considerably different from the conventional one. As a rule, the Hubbard relation is checked... 

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