Refractive index, density dependence

Correlation curves can be drawn by plotting either solution density or refracLive index against °Brix. The accurate estimation of solution water content would appear to be a trivial second step. However, this is so only if the solute is pure sucrose. Also, since both density and refractive index are dependent upon temperature, the temperature of measurement must be known, and a calibration curve valid for that temperature must be available. 

The Onsager function is dependent on the refractive index of the solvent (n). For supercritical C02 the refractive index is dependent on the fluid density and can be calculated from the Lorentz-Lorenz refraction equation ... 

Anisotropy While isotropy is homogeneity of a property (absorbance, refractive index, density, etc.) in all directions, anisotropy is the property of being directionally dependent. 

The most popular and simple method for structural bulk analysis for heavy crude oil fractions is called n-d-M analysis. The main idea behind this method is the linear dependence of aromatic, naphthenic and paraffinic carbon in heavy fraction on refractive index, density and value reverse to the molecular weight. This dependence is described by equation (2.23). 

Liquid crystalline phases are very important for the products having a high level of surfactants. The type of hquid crystalline phases formed depends on the nature of the surfactant, its level, the solvent mediiun, the additives, and the temperature of the medium [21-25], The various liquid crystalline phases have different physical properties, such as optical behavior, rheological properties, refractive index, density, and translucency. 

Existing methods for estimating aromatic contents use physical measurements, such as refractive index, density, and number average molecular weight (see Test Method D 3238) or infrared absorbance and often depend on the availability of suitable standards. These NMR procedures do not require standards of known aromatic hydrogen or aromatic carbon contents and are applicable to a wide range of hydrocarbon oils that are completely soluble in chloroform and carbon tetrachloride at ambient temperature. 

In methacrylic ester polymers, the glass-transition temperature, is influenced primarily by the nature of the alcohol group as can be seen in Table 1. Below the the polymers are hard, brittle, and glass-like above the they are relatively soft, flexible, and mbbery. At even higher temperatures, depending on molecular weight, they flow and are tacky. Table 1 also contains typical values for the density, solubiHty parameter, and refractive index for various methacrylic homopolymers. 

Melting points, boiling points, densities, and refractive indexes for carboxyUc acids vary widely depending on molecular weight, stmcture, and the presence of unsaturation or other functional groups (Tables 1,2,3, and 5). In addition, some useful constants for alkanoic acids are Hsted in Table 1. Some constants for selected unsaturated and substituted acids are given in Table 7. 

Ethers are unaffected by sodium and by acetyl (or benzoyl) chloride. Both the purely aliphatic ethers e.g., di-n-butyl ether (C4H, )30 and the mixed aliphatic - aromatic ethers (e.g., anisole C3HSOCH3) are encountered in Solubility Group V the purely aromatic ethers e.g., diphenyl ether (C,Hj)20 are generally insoluble in concentrated sulphuric acid and are found in Solubility Group VI. The purely aliphatic ethers are very inert and their final identification may, of necessity, depend upon their physical properties (b.p., density and/or refractive index). Ethers do, however, suffer fission when heated with excess of 67 per cent, hydriodic acid, but the reaction is generally only of value for the characterisation of symmetrical ethers (R = R ) ... 

The behavior of the different amines depends on at least four factors basicity, nucleophilicity, steric hindrance and solvation. In the literature (16), 126 aliphatic and aromatic amines have been classified by a statistical analysis of the data for the following parameters molar mass (mm), refractive index (nD), density (d), boiling point (bp), molar volume, and pKa. On such a premise, a Cartesian co-ordinate graph places the amines in four quadrants (16). In our preliminary tests, amines representative of each quadrant have been investigated, and chosen by consideration of their toxicity, commercial availability and price (Table 1). 

The pH optical fiber sensor without any pH-sensitive dye was also described70. Porous silica layer made by the sol-gel method was cladded onto optical fibre core and was exploited as the optical transducer. Acid-base properties of silica surface caused that the surface charge of silica changed with pH of the solution. For example saturation of the sol-gel layer with cations leads to an increase of the electron density of the film, hence, the refractive index of the film. Since the surface charge of silica depends on pH, the refractive index of silica film varies also with pH. Thus, changes of... 

The dependence of PS porosity on doping density has been exploited to fabricate optical waveguides. Such structures require only a single variation of refractive index. If a p-type substrate with implanted p+ lines is anodized and partially oxidized, mesoporous lines of high refractive index are embedded in a low refractive index material. An obtained refractive index contrast between core and clad of 30% is promising for future applications [Tal2]. 

The measurement of the width of the metastable zone is discussed in Section 15.2.4, and typical data are shown in Table 15.2. Provided the actual solution concentration and the corresponding equilibrium saturation concentration at a given temperature are known, the supersaturation may be calculated from equations 15.1-15.3. Data on the solubility for two- and three-component systems have been presented by Seidell and Linkiv22 , Stephen et alS23, > and Broul et a/. 24. Supersaturation concentrations may be determined by measuring a concentration-dependent property of the system such as density or refractive index, preferably in situ on the plant. On industrial plant, both temperature and feedstock concentration can fluctuate, making the assessment of supersaturation difficult. Under these conditions, the use of a mass balance based on feedstock and exit-liquor concentrations and crystal production rates, averaged over a period of time, is usually an adequate approach. 

In the equation s is the measured dielectric constant and e0 the permittivity of the vacuum, M is the molar mass and p the molecular density, while Aa and A (po2) are the isotope effects on the polarizability and the square of the permanent dipole moment respectively. Unfortunately, because the isotope effects under discussion are small, and high precision in measurements of bulk phase polarization is difficult to achieve, this approach has fallen into disfavor and now is only rarely used. Polarizability isotope effects, Aa, are better determined by measuring the frequency dependence of the refractive index (see below), and isotope effects on permanent dipole moments with spectroscopic experiments. 

The sample size required depends on the viscosity of the sample, the cell size of the density measurement device and the refractive index instrument. The density measurement requires a sample size of about 7-10 ml and the measurement must be made after a stabihzation period with no flow. In contrast, the refractive index measurement is made on a flowing stream. 

It is appropriate at this point to briefly discuss the experimental procedures used to determine polymerization rates for both step and radical chain polymerizations. Rp can be experimentally followed by measuring the change in any property that differs for the monomer(s) and polymer, for example, solubility, density, refractive index, and spectral absorption [Collins et al., 1973 Giz et al., 2001 McCaffery, 1970 Stickler, 1987 Yamazoe et al., 2001]. Some techniques are equally useful for step and chain polymerizations, while others are more appropriate for only one or the other. Techniques useful for radical chain polymerizations are generally applicable to ionic chain polymerizations. The utility of any particular technique also depends on its precision and accuracy at low, medium, and high percentages of conversion. Some of the techniques have the inherent advantage of not needing to stop the polymerization to determine the percent conversion, that is, conversion can be followed versus time on the same reaction sample. 

Soft crystalline solid rhombic crystal pure salt is white but color may vary the color of the mineral barite may vary among red, yellow, gray or green depending on impurities density 4.50 g/cm refractive index 1.64 melts around 1,580°C decomposes above 1,600°C hardness 4.3 to 4.6 Mohs insoluble in water (285 mg/L at 30°C) and alcohol Ksp 1.1 x 10-i° soluble in concentrated sulfuric acid. 

In diffuse reflection spectroscopy, the spectrometer beam is reflected from, scattered by, or transmitted through the sample, whereas the diffusely scattered light is reflected back and directed to the detector. The other part of the electromagnetic radiation is absorbed or scattered by the sample [124,125]. Changes in band shapes or intensity as well as signal shifts can be affected by morphological and physicochemical properties of the sample or combinations thereof (e.g., chemical absorptions, particle size, refractive index, surface area, crystallinity, porosity, pore size, hardness, and packing density [126]). Therefore, NIR diffuse reflection spectra can be interpreted in dependence of various physical parameters [127]. 

Refractive Index and Dispersion. The velocity of light varies depending upon the density of the medium in which it is propagating. In a vacuum, the speed of light is a constant, c, which has a value of 3.08 x 10 m/s. In any other medium, such as a gas, liquid, or solid, the velocity is given by the variable, v. The ratio between these two velocities determines the index of refraction, n, sometimes called the refractive index ... 

The effect of electromagnetic radiation on matter is to induce a dipole. In a transparent dielectric medium, only the velocity of electromagnetic radiation is reduced, depending on the refractive index of the medium, which is determined by its density. The propagation constant of electromagnetic waves is given by... 

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