Abbe refractometer technique

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. 

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]. 

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 ... 

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