Becke line technique

Bechamp batch process Bechamp reaction Beck and Guthke cell Becke line technique... 

Brewster s law. Reflected light in general is more polarised than the incident light and according to Brewster s law, the polarisation is maximum when i + r = 90 where i and r are the angles of incidence and refraction. There are several methods described in the literature such as those based on the use of prisms and fluid immersion (in fluids of known refractive indices) and index matching. The so-called Becke line technique for index matching uses observations under microscope. 

General methods of measuring refractive index, not confined to plastics, can be found in older textbooks on optics [3]. Well-known methods arc those depending on matching the unknown solid with known liquids, using the Becke line technique [4], dispersion staining [5], techniques based on the Abbe refractometer [3], and the measurement of the ratio of real depth to apparent depth [3]. 

The two methods recommended in ISO 489 [6] are the Abbe refractometer technique and the Becke line technique. 

The two measurement methods recommended by IS0489 are the Abbe refractometer technique and the Becke line technique. The latter is more useful with powdered or granulated transparent material or even with small chips of material taken from a larger sample. ASTM D542 includes only the Abbe method and it is widely used for characterization of refractive index of polymers. 

Approximate measurements of refractive index may be made by the Becke line technique. With this, a small chip of glass having a sharp edge is immersed in standardized refractive index oil on the stage of a transmission optical microscope illuminated by a monochromatic light source. The distance between the microscope objective and the... 

Using the Becke line (or other comparative re fractive-index techniques) determine whether the particle has an index higher or lower than the RI of the liquid. Wash off the liquid and cover glass with a gentle stream of xylene over a container that can be sealed for safe storage and disposal. 

It should be mentioned that it is possible to determine solid-solid phase transitions by the Morey technique. In this case solids are heated for extended periods above and below a transition temperature and identification of a ciystal form may be made either by X-ray analysis or by microscopic examination, as with a Becke line refractive index analysis. Once the refractive indexes of the two crystal forms are established, walking in on a transition can be done in much the same way a melting point can be established. 

Measurement of Refractive Indexes. Some of the techniques used to measure refractive indexes are the Becke line method (94), interference microscopy (95,96), Abbe refractometer (40,94,97-99), and ellipsometry (100). The Abbe re-fractometer (Fig. 5) can be used to determine the refractive indexes of materials belonging to all three optical symmetries. Its principle is based on the total reflection phenomenon occurring between a known and unknown isotropic media ... 

Lustig, S., Michalke, B., Beck, W. and Schramel, R (1998) Platinum speciation with hyphenated techniques high performance liquid chromatography and capillary electrophoresis on-line coupled to an inductively coupled plasma mass spectrometer -application to aqueous extracts from a platinum treated soil. Fresenius J. Anal. Chem., 360,18-23. 

The focus of most archaeological ceramic studies has been on provenance or technology. There is also a growing body of specific evidence on how the pottery was used. Chapter 21 by Beck, Smart, and Ossenkop describe the organic tars used to line ancient Mediterranean amphoras. Chapter 21 includes a description of how the residues from amphora contents can be analyzed. As in most cases where unknown organic materials are encountered, the most powerful analytical technique is gas chromatography with mass spectrometric detection (GC-MS). This technique is expensive for the analysis of large numbers of samples. 

The infrared spectrum (KBr disks) was recorded on a Perkin-Elmer 683 spectrometer (range 4000-200 cm 1, calibrated with polystyrene lines) and was found to be superimposable on that given in Ref. 26. This spectrum was used by Becke-Goehring and Boppel as evidence for the ANSA structure. It is demonstrated below how careful one has to be when assigning a certain molecular configuration on the bases of indirect structural techniques such as IR spectroscopy. 

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