Refractive index product

As a consequence, other than its use in the ndM method, the refractive index is very often used in process operations because it can indicate smaii differences in product quality that would be missed by other measurements. The only restriction is that the color of the sample should be less than 5 on the ASTM D 1500 scale. 

Note 1. At higher temperatures the tertiary chloride undergoes a rearrangement, catalysed by CuCl, giving H2C=C(C1)CH=CH2. In these cases the refractive index of the crude product is much higher. 

Sodium antimonate contains less antimony than either antimony trioxide or pentoxide and is thus less effective. However, its unique pH and low refractive index makes the antimonate the most desirable synergist for polymers that hydrolyze when processed with acidic additives or in polymers for which deep color tones are specified. Sodium antimonate costs approximately 3.30—4.40/kg and can be obtained from either Elf Atochem NA under the Thermoguard name or from Anzon Inc. as a Timinox product. 

Eor purposes of product identification and quaUty control it is useful not only to employ the abovementioned analytical methods but also to measure physical constants such as the density, refractive index, melting point, and pH value of the material. 

The final product of all the above processes is iron(III) oxide, a-Fe202, but its properties are deterrnined by the method of preparation. Thermal dehydration of goethite yields a pigment of lowest (4.5 g/cm ) density. The highest (5.2 g/cm ) density pigment is one prepared by two-stage calcination. The particle si2e varies from 0.3 to 4 p.m the refractive index varies from 2.94 to 3.22. 

Capillary gc/ms, hplc, nmr, ir, and uv are all analytical methods used by the terpene chemist with a good Hbrary of reference spectra, capillary gc/ms is probably the most important method used in dealing with the more volatile terpenes used in the davor and fragrance industry (see Flavors and spices). The physical properties of density, refractive index, boiling point, melting point of derivatives, and specific rotation are used less frequendy but are important in defining product specifications. 

Various polymers, such as polythiourethanes, polythioethers, and polythioacrylates, are used to produce resins which are transparent, colorless and have a high refractive index and good mechanical properties, useful for the production of optical lenses. Higher refractive indices are promoted by sulfur compounds and especially by esters of mercaptocarboxyhc acids and polyols such as pentaerythritol (41) (see Polymers containing sulfur). 

In the glass (qv) and ceramic industry (see Ceramics), barite can be used both as a flux, to promote melting at a lower temperature or to increase the production rate, and as an additive to increase the refractive index of glass. The viscosity of barite-containing glass often needs to be raised. Alumina in the form of feldspar is sometimes used. To offset any color produced by iron from the barite addition, more decolorizer may be needed. When properly used, barytes help reduce seed, increase toughness and brilliancy, and reduce annealing time. Barite is also a raw material for the manufacture of other barium chemicals. 

Other Applications. The refractive index of siUcate or borosiUcate glass can be modified by the addition of cesium oxide, introduced as cesium nitrate or carbonate. Glass surfaces can be made resistant to corrosion or breakage by surface ion exchange with cesium compound melts or solutions. This process can also be used for the production of optical wave guides (61). 

When the disperse phase has a slightly higher refractive index the compound tends to be blue when it is lower than that of the PVC the compound tends to be yellow and hazy. In order to overcome this a carefully determined quantity of a second MBS additive, with an appropriate refractive index and whieh is compatible with the PVC compound and hence forms a continuous phase with it, may be added to match the refractive indices. Such a matching operation should be evaluated at the proposed serviee temperature range of the product since the temperature coefficients of the two phases are usually different and a film which is blue at proeessing temperature may become yellow at 20°C. 

As mentioned earlier, unmodified polystyrene first found application where rigidity and low cost were important prerequisites. Other useful properties were the transparency and high refractive index, freedom from taste, odour and toxicity, good electrical insulation characteristics, low water absorption and comparatively easy processability. Carefully designed and well-made articles from polystyrene were often found to be perfectly suitable for the end-use intended. On the other hand the extensive use of the polymers in badly designed and badly made products which broke only too easily caused a reaction away from the homopolymer. This resulted, first of all, in the development of the high-impact polystyrene and today this is more important than the unmodified polymer (60% of Western European market). 

The undistilled />-methoxyphenylacetonitrile weighs 125-139 g. (85-95%) and has a refractive index close to that of the distilled product. It can be used for many purposes, such as... 

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