Refractive index carbonate, calculation

One method (ASTM D-2501) describes the calculation of the viscosity-gravity coefficient (VGC)—a parameter derived from kinematic viscosity and density that has been found to relate to the saturate/aromatic composition. Correlations between the viscosity-gravity coefficient (or molecular weight and density) and refractive index to calculate carbon type composition in percentage of aromatic, naphthenic, and paraffinic carbon atoms are used to estimate of the number of aromatic and naphthenic rings present (ASTM D-2140, ASTM D-3238). 

The TOTAL correlations calculate aromatic carbon content, hydrogen content, molecular weight, and refractive index using routine laboratory tests. The TOTAL correlations are listed below and are also in Appendix 3. Example 2-2 illustrates the use of TOTAL correlations. 

The n-d-M correlation is an ASTM (D-3238) method that uses refractive index (n), density (d), average molecular weight (MW), and sulfur (S) to estimate the percentage of total carbon distribution in the aromatic ring structure (% C ), naphthenic ring structure (Cj,), and paraffin chains (% Cp). Both refractive index and density are either measured or estimated at 20°C (68°F). Appendix 4 shows formulas used to calculate carbon distribution. Note that the n-d-M method calculates, for example, the percent of carbon in the aromatic ring... 

To a distillation flask is added 29.0 gm (0.244 mole) of 3-bromopropyne and 2.5 gm (0.0174 mole) of dry cuprous bromide. The flask is attached to a concentric-tube column (25-30 theoretical plates), and the temperature of the flask is controlled so that the takeoff temperature at the head remains at 72.8°-73.5°C. In 24 hr, 24.4 gm (84 %) of bromopropadiene of 75-85 % purity is obtained. The remaining 3-bromopropyne (propargyl bromide) is removed by washing the product with a 40 % aqueous solution of diethylamine. Three to four moles of diethylamine is used for each mole of propargyl bromide in the product as calculated from VPC or refractive index data. After swirling the mixture (acidified with 15 % hydrochloric acid) for hr, the organic layer is separated, washed with water, dried over potassium carbonate, and distilled quickly under reduced pressure into a Dry Ice-cooled receiver to afford pure bromopropadiene, b.p. 72.8°C (9760 mm), w ° 1.5212, 1.5508. 

Table 5.16. Calculated electric-dipole polarizability for COj " and refractive index n of calcite in sodium D light, for carbon-oxygen distance = 1.29 A...

It is, therefore, hardly surprising that some confusion has arisen over the units in which detector sensitivity is measured. Instrument manufacturers have avoided the problem by not employing concentration as a unit of sensitivity, leaving the analyst to convert the detector sensitivity given in RI units %carbon etc. to g/ml of a given solute for calculation purposes. This might well be considered unreasonable by the analyst, who can not easily calculate the mass and concentration sensitivity of his/her equipment and often does not know the vapor thermal conductivity, the refractive index or electrical conductivity etc. of the solutes contained in the mixture being analyzed. Furthermore, in almost all analyses the mass concentration of the components are the quantity of real interest. 

The refractive index is also needed to calculate the refractivity intercept in the determination of carbon type composition (Speight, 2000). 

The influence of temperature on the mean dipole moment of polybutyl methacrylate dissolved in carbon tetrachloride is shown in Table II. The average moments were calculated from Frohlich s equation (see Section VI) taking unity as the most probable value of the correlation factor. Since the Onsager theory makes use of the refractive index of the solute, for which only approximate values can be found, results obtained by Onsager s and FrOhlich s theories for solutions are not identical even in a nonpolar solvent like carbon tetrachloride. The moments given in Table II are not comparable to those given in Table I, especially as they are not extrapolated to infinite dilution. 

The composition of carbon-chain polymers with monomeric units having widely differing analytical composition, characteristic elements or groups, or radioactive labels can be readily determined. Chemical (microanalysis, functional group determination, etc.) and spectroscopic methods (infrared, ultraviolet, nuclear magnetic resonance, etc.), as well as the determination of radioactivity, yield the average composition of the polymer. The mean composition can also be determined from the refractive indices of solid samples. The composition can be calculated from the principle that the copolymer is considered to be a solution of one unipolymer (from one of the monomeric units) in the other. The composition can also be found by means of the refractive index increment dw/dc in solution, which gives the variation in refractive index with concentration. The mass fraction of the monomeric unit A can be calculated from... 

The optical path length of a wave in a material of thickness t is nt, as the material contains nt/X wavelengths as would a path of length nt in vacuum. The optical path difference A due to the presence of this material is then n — l)t, and the phase difference produced is (Iw/X) A. Table 3.1 shows how the optical properties of polyst)n"ene depend on the incident radiation. The refractive index of polystyrene for electrons is calculated from values for carbon, corrected for the lower density of polystyrene (see Section 3.1 of ref. 5). 

---