Refractive index temperature coefficient

Material Refractive index Temperature coefficient of refraction dn/dT (10 oC ) Abb6 value... 

By an assortment of thermodynamic manipulations, the quantities dn/dp and [N (d G/dp )o] can be eliminated from Eq. (10.48) and replaced by the measurable quantities a, /3, and dn/dT the coefficients of thermal expansion, isothermal compressibility, and the temperature coefficient of refractive index, respectively. With these substitutions, Eq. (10.48) becomes... 

Optical Properties. The index of refraction and extinction coefficient of vacuum-deposited aluminum films have been reported (8,9) as have the total reflectance at various wavelengths and emissivity at various temperatures (10). Emissivity increases significantly as the thickness of the oxide film on aluminum increases and can be 70—80% for oxide films of 100 nm. 

T[ at 25°C, mm /s(=cSt) viscosity—temperature coefficient density, g/mL refractive index pour point, °C... 

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. 

The transition between crystalline and amorphous polymers is characterized by the so-called glass transition temperature, Tg. This important quantity is defined as the temperature above which the polymer chains have acquired sufficient thermal energy for rotational or torsional oscillations to occur about the majority of bonds in the chain. Below 7"g, the polymer chain has a more or less fixed conformation. On heating through the temperature Tg, there is an abrupt change of the coefficient of thermal expansion (or), compressibility, specific heat, diffusion coefficient, solubility of gases, refractive index, and many other properties including the chemical reactivity. 

Special care has to be taken if the polymer is only soluble in a solvent mixture or if a certain property, e.g., a definite value of the second virial coefficient, needs to be adjusted by adding another solvent. In this case the analysis is complicated due to the different refractive indices of the solvent components [32]. In case of a binary solvent mixture we find, that formally Equation (42) is still valid. The refractive index increment needs to be replaced by an increment accounting for a complex formation of the polymer and the solvent mixture, when one of the solvents adsorbs preferentially on the polymer. Instead of measuring the true molar mass Mw the apparent molar mass Mapp is measured. How large the difference is depends on the difference between the refractive index increments ([dn/dc) — (dn/dc)A>0. (dn/dc)fl is the increment determined in the mixed solvents in osmotic equilibrium, while (dn/dc)A0 is determined for infinite dilution of the polymer in solvent A. For clarity we omitted the fixed parameters such as temperature, T, and pressure, p. 

Notice, that with these extremely good resolutions in case of surface sensing contamination of the sensitive layer with solid particles has to be avoided completely, e.g. by an appropriate filtering of the sample solutions. Notice also that the temperature coefficient of the refractive index of water is about 10-4 per °C. So if applying the surface sensing mode using watery solutions indeed a perfect balance of both branches and low temperature gradients have to be aimed at. 

The physical properties of solvents greatly influence the choice of solvent for a particular application. The solvent should be liquid under the temperature and pressure conditions at which it is employed. Its thermodynamic properties, such as the density and vapor pressure, temperature and pressure coefficients, as well as the heat capacity and surface tension, and transport properties, such as viscosity, diffusion coefficient, and thermal conductivity, also need to be considered. Electrical, optical, and magnetic properties, such as the dipole moment, dielectric constant, refractive index, magnetic susceptibility, and electrical conductance are relevant, too. Furthermore, molecular... 

C poly 1,4-isoprene has a specific gravity of 0.91, a coefficient of linear expansion of 67 X 10 9 cm/cm C, and a refractive Index of 1.5191. This and other elastomers retain their characteristic mobility at temperatures above the Tt. They are brittle at temperatures below Tg. 

Glass transition temperature is one of the most important parameters used to determine the application scope of a polymeric material. Properties of PVDF such as modulus, thermal expansion coefficient, dielectric constant and loss, heat capacity, refractive index, and hardness change drastically helow and above the glass transition temperature. A compatible polymer blend has properties intermediate between those of its constituents. The change of glass transition temperature has been a widely used method to study the compatibility of polymer blends. Normally, the glass transition temperatme of a compatible polymer blend can be predicted by the Gordon-Taylor relation ... 

The methods of measuring the liquid phase properties were described previously [1], It was observed that heat was evolved during the preparation of all these mixtures. It should be mentioned that the electrical conductivities of the sulphuric acid-nitromethane mixtures were not constant, but were found to increase with time. Reliable data could therefore not be obtained. This is due to the fact that nitromethane reacts with sulphuric acid in dilute solutions, as has been recently discussed by Gillespie and Solomons [6]. All other properties of these mixtures were constant at 25° and measurements were restricted to this temperature. For the other four systems the viscosity, electrical conductivity and density were investigated at two temperatures 25° and 40°), because of the importance of the temperature coefficients of viscosity and electrical conductivity. The refractive indexes were measured only at 25°. The investigation of the liquid phase properties of the system with p-nitro toluene at these temperatures was possible only up to 50 mole % of p-nitrotoluene, i.e. until the solutions became saturated with respect to p-nitrotoluene. The refractive indexes of these solutions were not measured. 

Tg can be determined by studying the temperature dependence of a number of physical properties such as specific volume, refractive index, specific heat, etc. First-order transitions, such as the melting of crystals, give rise to an abrupt change or discontinuity in these properties. However, when a polymeric material undergoes a second-order transition, it is not the primary property (the volume), but its first derivative with respect to temperature, (the coefficient of expansion), which becomes discontinuous. This difference between a first and second-order transition is illustrated in Figure 10. 

Octahedral sulphur is a brittle solid of hardness approximately 2-3 the colour is lemon-yellow at the ordinary temperature but darkens somewhat on warming, whilst at —50° C. it almost disappears, leaving the solid practically colourless 6 the refractive index for sodium light is 2-08,7 the mean specific heat is 0-170,8 and the coefficient of cubic... 

The liquid has a coefficient of expansion of 0-0020058 for the temperature range 15° to 20° C., a refractive index, Wp°°=1-40965,9 and boils at 44-8° C. under 760 mm. pressure.10 When kept at a temperature below 25° C. for a considerable period, it undergoes gradual conversion into the more stable /3-form, which slowly separates for this reason the earlier boiling-point data in the literature show considerable variation. Experiments with solutions of sulphuric acid, sulphonal and trional in the liquid indicate a value of 13-5 for the ebullioseopic constant.l L... 

Optical Properties.—The refractive index of tantalum is 2-05, the coefficient of absorption 2-31, and the reflexion capacity 43-8 per cent, when measured with yellow light of wave-length A=5790.5 The spectral emissivity and the radiation intensity and their variation with temperature have been measured by Worthing.6 For a comparison of the radiation constants of tantalum, platinum, osmium and carbon, see the references cited.7 The flame spectrum of tantalum between carbon electrodes consists of a blue cone with a reddish-yellow edge.8... 

Increase in temperature causes a slight decrease in refractive index. The heat of dissolution 4 of the octahedral form is - 7530 calories at 18° C. The velocity of crystallisation from supersaturated solutions corresponds with 5 - dcjdt = fre4, where c is the concentration the temperature coefficient for the interval 0 to 25° C. is zero. 

Selected compound-specific functions, property-temperature-property relationships, or structure-temperature-property relationships are supplied and discussed in this book for density (Section 3.5), refractive index (Section 4.5), surface tension (Section 5.4), viscosity (Section 6.4), vapor pressure (Section 7.4), enthalpy of vaporization (Section 8.5), aqueous solubility (Section 11.8), and air-water partition coefficients (Section 12.5). 

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