Refractive index fractions

Refractive Index. The refractometric value of sugar solutions is used as a rapid method for the approximate determination of the soHds content (also known as dry substance), because it is assumed that the nonsugars present have a similar influence on the refractive index as sucrose. Measurement is usually carried out on a Brix refractometer, which is graduated in percentage of sucrose on a wt/wt basis (g sucrose/100 g solution) according to ICUMSA tables of refractive index at 20.0°C and 589 nm. Tables are available that give mass fraction corrections to refractometric values at temperatures different from 20°C. 

T and are the glass-transition temperatures in K of the homopolymers and are the weight fractions of the comonomers (49). Because the glass-transition temperature is directly related to many other material properties, changes in T by copolymerization cause changes in other properties too. Polymer properties that depend on the glass-transition temperature include physical state, rate of thermal expansion, thermal properties, torsional modulus, refractive index, dissipation factor, brittle impact resistance, flow and heat distortion properties, and minimum film-forming temperature of polymer latex... 

Bromine (128 g., 0.80 mole) is added dropwise to the well-stirred mixture over a period of 40 minutes (Note 4). After all the bromine has been added, the molten mixture is stirred at 80-85° on a steam bath for 1 hour, or until it solidifies if that happens first (Note 5). The complex is added in portions to a well-stirred mixture of 1.3 1. of cracked ice and 100 ml. of concentrated hydrochloric acid in a 2-1. beaker (Note 6). Part of the cold aqueous layer is added to the reaction flask to decompose whatever part of the reaction mixture remains there, and the resulting mixture is added to the beaker. The dark oil that settles out is extracted from the mixture with four 150-ml. portions of ether. The extracts are combined, washed consecutively with 100 ml. of water and 100 ml. of 5% aqueous sodium bicarbonate solution, dried with anhydrous sodium sulfate, and transferred to a short-necked distillation flask. The ether is removed by distillation at atmospheric pressure, and crude 3-bromo-acetophenone is stripped from a few grams of heavy dark residue by distillation at reduced pressure. The colorless distillate is carefully fractionated in a column 20 cm. long and 1.5 cm. in diameter that is filled with Carborundum or Heli-Pak filling. 4 hc combined middle fractions of constant refractive index are taken as 3-l)romoaccto])lu iu)nc weight, 94 -100 g. (70-75%) l).p. 75 76°/0.5 mm. tif 1.57,38 1.5742 m.]). 7 8° (Notes 7 and 8). 

Degassed and preswelled Bio-Gel P-6 and Sephacryl S-200 were packed in self-made glass columns (70 X 1.5 cm 140 X 1.5 cm) and equilibrated for 20 hr with H20(dest.) -t- 0.002% NaN3 to prevent microbial growth. The mass of eluted fractions was detected with a differential refractive index detector (Waters 403 RI, sensitivity 8). 

These combined HDF and GPC separations require the use of detectors such as static light scattering or viscometers to help sort out the convoluted elution profiles seen in those type of experiments. It should also be remembered in these situations that the typical refractive index or ultraviolet detector responses may not be representative of the actual mass fraction of insolubles eluting from the column because of the significant light scattering that can occur with those large particles in the detector cell. 

In 1899 Thoms isolated an alcohol from Peru balsam oil, which he termed peruviol. This body was stated to have powerful antiseptic properties, but has not been further investigated until Schimmel Co. took up the subject. The oil after saponification was fractionated, and after benzyl alcohol had distilled over, a light oil with characteristic balsamic odour passed over. It boiled at 125° to 127° at 4 mm., and had a specific gravity 0 8987, optical rotation -1- 12° 22, and refractive index 1-48982. This body appeared to be identical with Hesse s nerolidol, whilst in physical and chemical properties it closely resembles peruviol. The characters of the various preparations were as follows —... 

The specific gravity, refractive index, and specific rotation given above are those recorded by Paolini and Divizia and are probably accurate since the a-santalol was prepared by regeneration from its strychnine phthalate. The values recorded for commercial santalol, prepared by fractional distillation, are as follows, and are the average values for the mixed santalols as they occur in sandalwood oil... 

The author has recommended the examination of the last 10 per cent, left on evaporation of the oil on a water-bath, since the heavy artificial esters accumulate in this fraction. The refractive index of this 10 per cent, should not be below 1 5090, and the saponification value should not exceed 190. The following figures (see p. 317) represent nine samples of adulterated oil, all sold as genuine bergamot oil. 

Petroleum or mineral oil (kerosene, etc.) are less soluble in alcohol than most oils. They have a low specific gravity and refractive index, and are not saponified by alcoholic potash. The lower boiling fractions can usually be detected by their odour, and the higher boiling fractions remain in the residue on fractional distillation. They are unaffected by fuming nitric acid. 

Water hydrolyzes diethyl phosphorochloridate [chloro-diethoxyphosphorus(V) oxide] readily but does not affect the diene. Alternatively, the reaction mixture can be processed by fractionation. Evaporation of the petroleum ether and fractionation of the residue through a 25-cm. x 2.2-cm. column of glass helices yields 170 g. (98.5%) of diethyl phosphorochloridate, b.p. 34-36°/0.2 mm., d 1.4210-1.4250 (the refractive index indicates that it contains 5-10% of the title compound), and 240-255 g. (90-96%) of l,2,3,4,5-pentachloro-5-ethylcyclo-pentadiene, b.p. 51-53°/0.2 mm., 1.5398. 

The molecular weight distribution of cell wall polysaccharides was estimated by gel filtration with a TOSOH TSK gel G4000 PWXL (7.8 x 300 mm) column equilibrated and eluted with 0.05 M sodium acetate, 0.01 M EDTA, 0.05 M NaCl (pH 5.0) in polyuronide and 0.05 M sodium citrate, 0.1 M NaCl (pH 5.5) in the hemicellulose fraction. Samples (1 mg/ml) of 100 ml were injected. The eluate was monitored by a refractive index detector (Shimadzu R1D-6A, Kyoto, Japan) and collected at the fraction size of 0.4 ml. 

Another variation of the preceding method is to apply HPLC to fractionate the cleaned-up aliphatic-aromatic fraction from flash colurim separation of soluble organic matter as it is performed in the Chevron laboratory, for example, as described in Reference 2. A Waters HPLC system equipped with a preparative Whatman Partisil 10 silica column (9.4 X 500 mm), a HPLC pump, and two detectors for separation monitoring (a UV and refractive index detector) are used, giving three fractions of aliphatic hydrocarbons, mono-, di-, and triaromatics and polar compounds. The hrst two fractions are eluted with hexane, whereas polar compounds are eluted with... 

Y Picoline. Commercially pure y-picoline contains )S-picoline and 2 6-lutidine and sometimes traces of non-basic impurities (aromatic hydrocarbons) which cannot be separated by fractionation. The non-basic impurities are removed by steam distillation of the base in dilute hydrochloric or sulphuric acid solution (for details, see under a Picoline). The impure y-picoline is converted into the zinc chloride complexes of the component bases the 2 6-lutidine - ZnClj complex is the least stable and upon steam distillation of the mixture of addition compounds suspended in water, 2 6-lutidine passes over flrst. The complete separation of the 2 6-lutidine may be detected by a determination of the density and the refractive index of the dry recovered base at varioiu stages of the steam distillation. The physical properties are —... 

The refractive index of amorphous silicon is. within certain limits, a good measure for the density of the material. If we may consider the material to consist of a tightly bonded structure containing voids, the density of the material follows from the void fraction. This fraction / can be computed from the relative dielectric constant e. Assuming that the voids have a spherical shape, / is given by Bruggeman [61] ... 

The microstructure parameter is low in the material deposited at the lowest power (Fig. 44e) it increases rapidly with increasing power up to 20 W, and then decreases again with further increasing power. The opposite holds for the refractive index (Fig. 44f), although that is less clear. A high value of the microstructure indicates a large fraction of Si—Ht bonds in the material, corresponding to an open material structure and a low refractive index. 

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