Optical microscopy 310 INDEX

Lab grade hematite (Fe203) and copper sulfate (anhydrous and hydrated) were mounted on slides and used as controls to compare to mineral deposits that might have been found adhering to foe fibers. Rabbit hair and milkweed that had been colored with an aqueous hematite solution and with an aqueous copper sulfate (blue vitriol) solution were also used for comparison. Fibers removed from each simulated material were mounted in water (Refractive Index (Rl) of 1.0), and in Permount (Fisher Scientific) (RI of 1.55). The collected particulate matter and fibers removed from foe yam samples were similarly mounted and examined using optical microscopy. 

Optical microscopy is another method that has been used to determine the distribution of minerals in coal. This method is based on the detailed microscopic examination of polished or thin sections of coal in transmitted and/or reflected light. In principle, observing several of its optical properties, such as morphology, reflectance, refractive index, and anisotropy, makes identification of a mineral type possible. 

Component of Optical Texture seen in Microscopy Abbreviation Size Optical Texture Index (0TI)... 

Induction times should decrease with an increase in supersaturation. Under constant supersaturation and all other variables constant, induction times will decrease with an increase in solubility, i.e., nucleation is faster in solvents providing high solubility. The induction time (formation of nuclei) can be detected by the appearance of crystals by optical microscopy or by changes in solution properties such as turbidity and refractive index. 

Optical microscopy has therefore shown (a) that the direction of maximum refractive index in the band (EDB) is parallel to the direction of maximum extension, (b) A pseudo-fibrillar texture is observed within the band which is not apparently related to the EDB nor to the direction a fibril in the drawn material would have if it followed an affine deformation in the band. WAXS measurements reveal, further, that the preferred crystallographic c-axis direction is neither parallel to the pseudo-fibrils nor to the extinction direction in the band (EDB). The WAXS photographs from material within the bands provide a clue to the explanation why the crystalline c-axes are not on average parallel to the maximum refractive index direction (EDB). For all materials examined (PET, PP... 

Phase-contrast optical microscopy (PCOM) is used mainly for assessment of the refractive index in comparison with liquids of standard index. Next PCOM is widely used to measure fiber concentration. Before examination of the sample, acid treatment may be used to remove carbonates from cement matrices, or organic solvents may be necessary to remove plastic binder materials. OM operates at magnifications of only 400 x and will not resolve fibers below 0.25 pm in diameter. Furthermore, PCOM caimot distinguish asbestos fibers from other fibers (e.g., gypsum, mineral wool, fiberglass, cellulose, etc.). 

These examples cQso illustrate the difference in spatial resolution and contrast mechanisms between optical and infrared microscopies. While optical microscopy is capable of higher spatial resolution, its discrimination is limited to a difference in the average of a property of materials, namely refractive index, unless specially labeled to detect a property of the label. Infrared microspectroscopy derives its contrast mechanism from the intrinsic composition of the material but suffers from a poorer spatial resolution. A judicious use of the two complementary techniques is often required to achieve good characterization. While the example above illustrated the detection of differences, FTIR microspectroscopy can also be used to determine homogeneity. For example, compositional differences in a PP-PE film could not be detected between the surface and up to 500 pm into the bulk of the sample [61]. 

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