Acetate INDEX

Lead oxide is used in producing fine "crystal glass" and "flint glass" of a high index of refraction for achromatic lenses. The nitrate and the acetate are soluble salts. Lead salts such as lead arsenate have been used as insecticides, but their use in recent years has been practically eliminated in favor of less harmful organic compounds. 

Testing. Melt index or melt flow rate at 190°C, according to ASTM D1238, is the test most frequently appHed to the characterization of commercial acetal resins. The materials are typically grouped or differentiated according to their melt flow rate. Several other ASTM tests are commonly used for the characterization and specification of acetal resins. 

The weight average molecular weight of acetal copolymers may be estimated from their melt index (MI, expressed in g/10 min) according to the relation... 

Many grades of acetal resins are Hsted in Underwriters Eaboratories (UL) Kecogni d Component Directory. UL assigns temperature index ratings indicating expected continuous-use retention of mechanical and electrical properties. UL also classifies materials on the basis of flammability characteristics homopolymer and copolymer are both classified 94HB. 

Refractive Index. The refractive index parallel to the fiber axis (s) is 1.478 for acetate and 1.472 for triacetate. The index perpendicular to the axis (co) is 1.473 for acetate and 1.471 for triacetate. The birefringence, ie, the difference between S and CO, is very low for acetate fiber and practically undetectable for triacetate. 

The bulk density of cellulose acetate varies with physical form from 160 kg/m (10 lb /ft ) for soft dakes to 481 kg/m (30 lb /fT) for hammer-milled powder, whereas the specific gravity (1.29—1.30), refractive index (1.48), and dielectric constant of most commercial cellulose acetates are similar. 

Poly(vinyl acetate) is too soft and shows excessive cold flow for use in moulded plastics. This is no doubt associated with the fact that the glass transition temperature of 28°C is little above the usual ambient temperatures and in fact in many places at various times the glass temperature may be the lower. It has a density of 1.19 g/cm and a refractive index of 1.47. Commercial polymers are atactic and, since they do not crystallise, transparent (if free from emulsifier). They are successfully used in emulsion paints, as adhesives for textiles, paper and wood, as a sizing material and as a permanent starch . A number of grades are supplied by manufacturers which differ in molecular weight and in the nature of comonomers (e.g. vinyl maleate) which are commonly used (see Section 14.4.4)... 

Ethylenevinylacetate (EVA) is the most used type (approximately 80%) it can be varied in viscosity (melt index) and content of acetate in broad ranges. It is semicrystalline. The vinyl acetate groups provide improved adherability towards many materials. The low heat stability, however, limits the areas of application. 

For acrylate polymers with higher levels of carboxylic acids, THF can be modified by the addition of acids such as acetic, phosphoric, or trifluoroacetic. Levels as high as 10% acetic acid are considered acceptable by most manufacturers for their styrene/DVB columns. If such a modified mobile phase is used, it may need to be premixed rather than generated using a dynamic mixing HPLC pump because on-line mixing often leads to much noisier baselines, particularly when using a refractive index detector. 

II forms an acetate of specific [avltv I Olhri ai 20" and rciraelive index 1-2021. 

The specific gravity ol the crude oil at C. = 0 S705 rotation a = -(- 15-1 relractiTe index at23 C. = lAtHl. The saponification number is 2 4, equal to (l 84 per cent, of ester as bornyl or gemoyl acetate. 

If myrcene be heated with glacial acetic acid to 40° for three to four hours, with the addition of a little sulphuric acid, hydration takes place, and an alcohol, which is termed myrcenol is formed. This body is an oil, of specific gravity 0 9032, refractive index 1 4806 at 15°, and boiling-point 99° at 10 mm. pressure. It yields a phenylurethane melting at 68°. 

On oxidation with chromic acid in acetic acid solution, dihydrocarveol yields dihydrocarvone, which has a specific gravity 0 928 at 19°, and refractive index 1-47174. The dihydrocarvone from Zae o-dihydro-carveol is dextro-rotatory, and -vice versa. Its oxime melts at 88° to 89° for the optically active variety, and at 115° to 116° for the optically inactive form. 

Benzyl Acetate.—This ester is a constituent of the oils of jasmin, ylang-ylang, and similar flower oils. It has not a very intense odour, but is essential to the successful production of such perfumes as artificial jasmin. It has the formula CgHg, CH2. O. OCCH3. It is a colourless oU, boiling at 206° at ordinary pressure, and has a specific gravity 1-0570 at 16° and a refractive index 1-5034 . The propionic ester has the formula C0H5CH2OOCCH2CH3, and closely resembles the acetate in odour. 

Glyceryl acetate is so easily washed out with ordinary hot distilled water, that an adulterated oil when washed several times with hot water will show a distinctly lower ester value and refractive index than the original unwashed oil. 

If the mixture to be separated contains fairly polar materials, the silica may need to be deactivated by a more polar solvent such as ethyl acetate, propanol or even methanol. As already discussed, polar solutes are avidly adsorbed by silica gel and thus the optimum concentration is likely to be low, e.g. l-4%v/v and consequently, a little difficult to control in a reproducible manner. Ethyl acetate is the most useful moderator as it is significantly less polar than propanol or methanol and thus, more controllable, but unfortunately adsorbs in the UV range and can only be used in the mobile phase at concentrations up to about 5%v/v. Above this concentration the mobile phase may be opaque to the detector and thus, the solutes will not be discernible against the background adsorption of the mobile phase. If a detector such as the refractive index detector is employed then there is no restriction on the concentration of the moderator. Propanol and methanol are transparent in the UV so their presence does not effect the performance of a UV detector. However, their polarity is much greater than that of ethyl acetate and thus, the adjustment of the optimum moderator concentration is more difficult and not easy to reproduce accurately. For more polar mixtures it is better to explore the possibility of a reverse phase (which will be discussed shortly) than attempt to utilize silica gel out of the range of solutes for which it is appropriate. 

As a measure of the stereoregularity, an index EQ-H% was defined as the precent of the equatorial acetal protons to the total acetal protons. Figure 2 illustrates the temperature dependence of EQ-H% s of the polymer obtained in toluene (A), methylene chloride (B), and 1-nitropropane (C). No significant difference is observed at... 

Substituents replacing the hydrogen atom of an alcoholic hydroxy group of a saccharide or saccharide derivative are denoted as O-substituents. The 0- locant is not repeated for multiple replacements by the same atom or group. Number locants are used as necessary to specify the positions of substituents they are not required for compounds fully substituted by identical groups. Alternative periphrase names for esters, ethers, etc. may be useful for indexing purposes. For cyclic acetals see 2-Carb-28. 

This index is divided into two parts. Part 1 gives the names of compounds as used in these volumes as well as general terms for classes of compounds, types of reactions, synthetic applications, special apparatus, and unfamiliar methods. The complete names of all specific compounds are given in normal order as written in the text (e.g., ethyl cyano-acetate appears under ethyl). Some entries are common names and others are systematic Chemical Abstracts names, whichever was used in the text. 

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. 

---