Refractive index under pressure

Measurements of the refractive index under pressure are necessary, in addition to the intrinsic refractive index as physical probes of condensed media, to interpret transmission measurements. This is most conveniently done under pressure by measuring Fabry-Perot interference patterns in plane-parallel samples. The position of the interference maxima in transmission is given by... 

The reaction mixture is heated and allowed to reflux, under atmospheric pressure at about 100°C. At this stage valve A is open and valve B is closed. Because the reaction is strongly exothermic initially it may be necessary to use cooling water in the jacket at this stage. The condensation reaction will take a number of hours, e.g. 2-4 hours, since under the acidic conditions the formation of phenol-alcohols is rather slow. When the resin separates from the aqueous phase and the resin reaches the requisite degree of condensation, as indicated by refractive index measurements, the valves are changed over (i.e. valve A is closed and valve B opened) and water present is distilled off. 

Eeptylic Aldehyde.—This aldehyde, also known as oenanthylic aldehyde, 18 formed by distilling castor oil under reduced pressure. It is an Oil of powerful fruity odour, boiling at 155°, or at 45° at 10 mm. pressure, and having a specific gravity 0-820, and refractive index 1-4150. It forms an oxime melting at 50°. 

To a solution of 93.8 g of the monoglycol ester in 500 ml of benzene, there are added 55 g of nicotinic acid chloride and 25 g of trimethylemine dissolved in 200 ml of benzene. The solution is stirred gently at a temperature of 60°C for two hours. After this time, the solution is cooled and washed successively with water, dilute hydrochloric acid, dilute ammonia and water until neutrality, it is dried over anhydrous sodium sulfate, and the sol vent Is evaporated under vacuum In this wey llOg of glycol 2-(p-chlorophenoxy)-2-methylpropionate nico-tlnate Is prepared, which represents a yield of 84%. The product is a sllghly yellow oil having a refraction index of no = 1.5422 and which is distilled with decomposition et 214°C at a pressure of 0.3 mm. 

Measurements of the common physical constants such as boiling point or refractive index are not sufficiently sensitive to determine the trace amounts of impurities in question. Besides the common spectroscopic methods, techniques like gas chromatography (GC), high-pressure liquid chromatography (HPLC), or thin-layer chromatography (TLC) are useful. The surest criterion for the absence of interfering foreign compounds lies in the polymerization itself the purification is repeated until test polymerizations on the course of the reaction under standard conditions are reproducible (conversion-time curve, viscosity number of the polymers). 

The anhydrous salt consists of white trigonal crystals refractive index 1.717 density 2.958 g/cm decomposes at 350°C practically insoluble in water (106 mg/L at room temperature) Ksp 1.0x10- low to moderate solubility under partial pressure of CO2 (3.5 and 5.9 g MgCOs/lOOg saturated solution at CO2 pressure 2 and 10 atm, respectively) insoluble in acetone and ammonia dissolves in acids. 

The Physical Properties are listed next. Under this loose term a wide range of properties, including mechanical, electrical and magnetic properties of elements are presented. Such properties include color, odor, taste, refractive index, crystal structure, allotropic forms (if any), hardness, density, melting point, boiling point, vapor pressure, critical constants (temperature, pressure and vol-ume/density), electrical resistivity, viscosity, surface tension. Young s modulus, shear modulus, Poisson s ratio, magnetic susceptibility and the thermal neutron cross section data for many elements. Also, solubilities in water, acids, alkalies, and salt solutions (in certain cases) are presented in this section. 

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... 

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. 

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... 

Dissolve 2.5 g of sodium hydroxide in 250 ml of water in a 500-ml two-necked flask fitted with a reflux condenser and a dropping funnel. Bring the solution to the boil, add rapidly from the dropping funnel 28.5 g (0.25 mol) of hexane-2, 5-dione (Expt 5.104) and continue to boil steadily under reflux for exactly 15 minutes (1). Cool the resulting dark-brown solution rapidly in an ice-salt bath, saturate with sodium chloride and extract with one 100 ml and two 50 ml portions of ether. Wash the ether extract with three 5 ml portions of water, dry over anhydrous sodium sulphate and remove the ether on a rotary evaporator. Distil the residual dark oil under reduced pressure and collect the colourless 3-methylcyclopent-2-enone as a fraction of b.p. 74-76 °C/ 16mmHg, n 0 1.4818 yield 9.5 g (40%). The product thus obtained is pure enough for most purposes when perfectly pure the refractive index is 1.4893. The product may darken on storage. 

It should be noted that also the refractive index in eq. (17) will change under pressure. This change can be estimated by the Lorenz local-field model, where the refractive index n is related to the atomic polarizability a p and the density of the material p by the Lorentz-Lorenz relation ... 

According to eq. (19) the refractive index increases with increasing density (increasing pressure) and increasing polarizability. However, this model is exactly valid only for point dipoles in a cubic arrangement. Therefore, the reliability of this model with respect to quantitative predictions is limited in many cases (Eremets, 1996). A further difficulty here is to estimate the change of the polarizability under pressure. 

The evaporation flask is now removed from the flash evaporator, and the residue (which may appear to be dry) is extracted under nitrogen or helium with three 25-ml. portions of anhydrous, peroxide-free diethyl ether. The ether extract is poured through a medium sintered-glass frit under an atmosphere of nitrogen or helium. Finally, the ether is removed by pumping on the filtered extract at 0°C. for 30-40 minutes. A pressure of less than 1 mm. is maintained. The colorless liquid product is identified as tri-n-butyltin hydride from its liquid-phase infrared spectrum11 and refractive index, n 1.4715, literature, 1.4711 (extrapolated from f> 1.472612 and 1.47206). The yield is 16.5 g. (0.057 mole, 96%). 

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