Solvents specification

Solvent Resistance. At temperatures below the melting of the crystallites, the parylenes resist all attempts to dissolve them. Although the solvents permeate the continuous amorphous phase, they are virtually excluded from the crystalline domains. Consequently, when a parylene film is exposed to a solvent a slight swelling is observed as the solvent invades the amorphous phase. In the thin films commonly encountered, equilibrium is reached fairly quickly, within minutes to hours. The change in thickness is conveniently and precisely measured by an interference technique. As indicated in Table 6, the best solvents, specifically those chemically most like the polymer (eg, aromatics such as xylene), cause a swelling of no more than 3%. 

The high fluorine content contributes to resistance to attack by essentially all chemicals and oxidizing agents however, PCTFE does swell slightly ia halogenated compounds, ethers, esters, and selected aromatic solvents. Specific solvents should be tested. PCTFE has the lowest water-vapor transmission rate of any plastic (14,15), is impermeable to gases (see also Barrierpolymers), and does not carbonize or support combustion. 

Generic name and description Breaking tenacity, g/denier Abrasion resistance Resistance to acids Resistance to alkalies Resistance to oxidizing agents Resistance to solvents Specific gravity Maximum operating temperature, "FI... 

The propionamide can be dried over CaO. H2O and unreacted propionic acid were removed as their xylene azeotropes. It was vacuum dried. Material used as an electrolyte solvent (specific conductance less than 10 ohm cm" ) was obtained by fractional distn under reduced pressure, and stored over BaO or molecular sieves because it readily absorbs moisture from the atmosphere on prolonged storage. [Hoover Pure Appl Chem 37 581 I974 Recommended Methods for Purification of Solvents and Tests for Impurities, Coetzee Ed., Pergamon Press, 1982.]... 

Can the unit be easily adapted to recover different solvents or is it solvent-specific ... 

Kennedy et al. found that the rate of the f-BuX + Me3Al model reaction is strongly affected by the nature of the halogen in MeX solvent, specifically the rates decreased... 

Recently, changes in the surface potential of some organic solvents, specifically ethylene glycol, y-butyrolactonej and dimethylo-sulfoxide upon adsorption of dipolar organic substances (e.g., chloroform and octanol) have been measured systematically for the first time. 

The reduction of this ester over Pd differed from the corresponding reaction over Pi in every important particular. Enantiomeric excess was low (high over Pt) and in the reverse sense (e g cinchonidine modification provided an S-excess in the product over Pd but an R-excess over Pt) Enantioselective reactions underwent self-poisoning over Pd (proceeded to completion over Pt), were of non-integral order (integral over Pt) and proceeded more slowly than reaction over unmodified catalyst (enhanced rate over Pt) Enantioselective reaction was solvent-specific over Pd (not over Pt) and was favoured by low catalyst reduction temperature (high reduction temperature for Pt)... 

Enolisation of ketones is favoured in alkanol solution, and the observed solvent specificity in this reaction may indicate that the formation of the enolic species C is favoured when ethanol is used as solvent. 

With the help of the o-profile the surface integral can be elegantly transformed into a o-integral (right side in Eq. 11), but we should keep in mind that the chemical potential of a solute in a solvent is essentially a surface integral of a solvent specific function over the surface of the solute. This fact is important for the analysis of the problem of solubiUty prediction. 

Accelerated solvent extraction (ASE) is a technique which attempts to merge the beneficial solvation properties of SFE with traditional organic solvents. Specifically, the sample is placed in an extraction vessel which can withstand high pressures while being maintained at a constant temperature. Extraction is carried out by pumping the extraction solvent through the samples for a limited time. As an example of the use of ASE, Richter and Covino extracted PCBs from a 10-g fish tissue sample with hexane... 

The general or universal effects in intermolecular interactions are determined by the electronic polarizability of solvent (refraction index n0) and the molecular polarity (which results from the reorientation of solvent dipoles in solution) described by dielectric constant z. These parameters describe collective effects in solvate s shell. In contrast, specific interactions are produced by one or few neighboring molecules, and are determined by the specific chemical properties of both the solute and the solvent. Specific effects can be due to hydrogen bonding, preferential solvation, acid-base chemistry, or charge transfer interactions. 

The GC/MS spectra were used to estimate the % depolymerization of TBMS under various conditions (see Table IV). The % depolymerization of polymer samples containing 2-nitrobenzyl tosylate is dependent upon the solvent used to cast films. When xylene is used, a higher % depolymerization is observed than with cyclohexanone. Moreover, the ratio of depolymerization products also varies with casting solvent. Specifically, the indan thermolysis product is more predominant when films were cast from xylene. The reaction with tosic acid hydrate resulted in a high degree of depolymerization this is most likely a consequence of depolymerization occurring during sample preparation. 

Solvents, specifically surrounding the sodium cation, lower its effect. In the presence of a crown ether, including and blockading the sodium cation, the rate of the final product formation is entirely restored. 

Here the pre-exponential factor At is the product of a temperature-dependent constant (ksT/h) = 2 X 10 °Ts where ke and h are the Boltzmann and Planck constants, and a solvent-specific coefficient that relates to both the solvent viscosity and to its orientational relaxation rate. This coefficient may be near unity for very mobile solvent molecules but may be considerably less than unity for viscous or orientationally hindered highly stractured solvents. The exponential factor involves the activation Gibbs energy that describes the height of the barrier to the formation of the activated complex from the reactants. It also describes temperature and pressure dependencies of the reaction rate. It is assumed that the activated complex is in equilibrium with the reactants, but that its change to form the products is rapid and independent of its environment in the solution (de Sainte Claire et al., 1997). 

Providing technical data on the solvent specifications and its application guideline. 

As anticipated above, the reactivity of the cyano complexes of transition metals are strongly influenced by the structure of the medium, namely the nature of the solvent (specific cyano-donor interactions), or the type and concentration of the counterions (15). Both of these factors have a profound influence in the electronic structure, and determine the observed changes in reactivity, particularly in... 

Eosin emission characteristics depend strongly on the solvent. Specifically transfer from aqueous solution to a nonaqueous solvent shifts the emission of Eosin toward longer wavelengths and increases the emission intensity. Wang and Cheung [142] have used the fluorescence enhancement of the Eosin label to study the association of troponin I with troponin C. Similarly Skou and Esmann [143] and Helmich de Jong et al. [144] have used Eosin itself as a fluorescent probe to study the conformational changes of enzymes involved in ionic transport. 

The nature of thiocyanato complexes of silver in non-aqueous solvents has recently been reassessed.145 IR and Raman spectra were used to show that when Ag+ was complexed by SCN, the species present and the equilibrium steps involved were solvent specific. Characteristic absorption bands are summarized in Table 24. In pyridine, complexation passed through [Ag2(SCN)]+ and AgSCN to [Ag(SCN)2], such that even when the [SCN ]T/[Ag+]T ratio was 0.059, 50% was present as the linear [Ag(SCN)2]- ion. 

Stoddard solvent—mineral spirits with a minimum flash point of 37.8°C (100°F), relatively low odor level, and other properties conforming to Stoddard solvent specifications, as described in test method ASTM D 484. Though formulated to meet dry cleaning requirements, Stoddard solvents are widely used wherever this type of mineral spirits is suitable. 

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