Visualization method refractive index

Flow patterns of hydrodynamic systems like the compendial dissolution apparatus may be qualitatively characterized by means of dilute dye injection (e.g., methylene blue) or by techniques using particulate materials such as aluminum powders or polystyrene particles. Flow patterns may be also visualized by taking advantage of density or pH differences within the fluid stream. The Schlieren method, for instance, is based on refraction index measurement. Hot wire anemo-metry is an appropriate method to quantitatively characterize flow rates. The flow rate is proportional to the cooling rate of a thin hot wire presented to the stream. Using laser Doppler... 

Figure 4. Comparison of the phase diagrams determined from the refractive index measurements with that obtained by the visual method. The weight fraction w is the concentration variable. Empty symbols are used, when the compositions are estimated from refractive index data (Cemim+BFJ in 1-butanol (A), 1-pentanol (y), 2-butanol (0), and 2-pentanol (<)), full symbols, when the data are obtained by the visual method observing the separation temperature in samples of different composition (Gemini+ in water ( ), 1-propanol (O). 1-butanol (A), 2-butanol (y), 1-pentanol (0), 2-pentanol (<), and 1-hexanol (>)).

This synthesis was announced in 1967 (396). Since then synthetic opals have become available from Gilson of Switzerland (397). These have the appearance of natural opal and many of the same properties, for example hydrated, density 2.113, refractive index 1.45, singly refractive, amorphous, hardness 6.15 mohs (398). The synthetic black opal is said to be indistinguishable from the natural ones by visual examination. Some difference in fluorescent properties was reported. The method of manufacture is a trade secret of the manufacturing company, Gilem S. A. 

A very powerful method to visualize index-matched particles uses fluorescent dyes and a laser sheet to illuminate a 2D cross section of a granular sample [238-243]. A schematic of the technique is shown on the left of Figure 2.6. Since the particles are index matched the light passes through without refraction and the laser sheet illuminates only a thin section of the sample. In the approximately... 

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