Retention degree

In a continuous set-up using Go-5, a considerable decrease in activity was also observed in comparison with the monomeric models. This effect was partly explained by deactivation of the catalyst due to the reaction of the catalytic units with the membrane or to some dendritic effect (due to the proximity of the unit centers leading to double or multiple phosphine complexation with the same palladium center), since the formation of a palladium black precipitate was observed on the membrane. Tests with the Go dendrimer model ligand (without palladium) showed a retention degree of 85%. This fact could also partly explain the decrease in activity due to the washout of catalyst during the reaction. However, a first-generation Gi-5 catalyst, with a higher retention, showed almost the same deactivation behavior. Thus, catalyst decomposition is most probably the main reason for the observed deactivation. 

Corey showed 1963 that 2-exo-103 and 2-endo-norbornylamines 104 are deaminat-ed in acetic acid to yield practically identical mixtures both in the exo endo product ratio and in the retention degree of optical activity. He postulated both reactions to the same intermediate classical 2-norbornyl cation since no optically active products were obtained from a symmetrical nonclassical 2-norbornyl ion 5. Somewhat later Berson studied the composition of reaction mixtures from the deamination of amines 103 and 104 (Table 8) more carefully three essential difference in the compositions of reaction mixtures were pointed out ... 

Fntrained Systems. In entrained systems, fine grinding and increased retention times intensify combustion but the temperature of the carrier and degree of dispersion are also important. In practice, the coal is introduced at high velocities which may be greater than 30 m/s and involve expansion from a jet to... 

The method used to apply and dry a fixative affects the degree of stiffness and hold it imparts to the hairstyle. If appHed and then manipulated with a comb, bmsh, or fingers as the polymer forms its film, the adhesive bonds between the hair are broken, the film coating the hair is broken, and the end result is a soft feel with Htde set retention. If the fixative is allowed to dry undisturbed, then the result is a firmer feel and better hold. 

Rosin sizing usually involves the addition of dilute aqueous solutions or dispersions of rosin soap size and alum to a pulp slurry (44—46). Although beater addition of either coreactant is permissable, addition of both before final pulp refining is unwise because subsequently exposed ceUulose surfaces may not be properly sized. The size and alum should be added sufficiendy eady to provide uniform distribution in the slurry, and adequate time for the formation and retention of aluminum resinates, commonly referred to as size precipitate. Free rosin emulsion sizes, however, do not react to a significant degree with alum in the pulp slurry, and addition of a cationic starch or resin is recommended to maximize retention of size to fiber. Subsequent reaction with aluminum occurs principally in the machine drier sections (47). 

Appllca.tlons. The first widely appHcable Ic separation of enantiomeric metallocene compounds was demonstrated on P-CD bonded-phase columns. Thirteen enantiomeric derivatives of ferrocene, mthenocene, and osmocene were resolved (7). Retention data for several of these compounds are listed in Table 2, and Figure 2a shows the Ic separation of three metallocene enantiomeric pairs. P-Cyclodextrin bonded phases were used to resolve several racemic and diastereomeric 2,2-binaphthyldiyl crown ethers (9). These compounds do not contain a chiral carbon but stiU exist as enantiomers because of the staggered position of adjacent naphthyl rings, and a high degree of chiral recognition was attained for most of these compounds (9). 

Autofiltration The retention of any material at the surface of the membrane gives rise to the possibility of a secondaiy or a dynamic membrane being formed. This is a significant problem for fractionation by ultrafiltration because microsolutes are partially retained by almost all retained macrosolutes. The degree of retention is quite case-specific. As a rule of thumb, higher pressure and more polarization resiilts in more autofiltration. Autofiltration is particularly problematic in attempts to fractionate macromolecules. 

On the other hand, not only initial colour but colour change (discolouration) of the resin under UV light and heat is important. Colour retention of a resin is related to the chemical stability and increases as the degree of non-aromatic conjugated unsaturation of the resin molecule decreases. Thus, for rosins a high level of abietic-type resin acids lead to relatively unstable resins. Hydrogenation and disproportionation as well as esterification provide improved stability and colour retention to rosins. 

Time refers to the retention time or residence which is the length of time that an organic is at the appropriate oxidation temperature. Roughly, if a 95% destruction efficiency is required, a residence time of a half a second is adequate. That is, the organic compound is brought up to a temperature of about 1400° F, and maintained at that temperature for a retention time of half a second. Both retention time and turbulence must be achieved, where turbulence is a term which implies a required degree of mixing. If the turbulence occurs and if the 1400° F for a half a second is... 

In selecting cloths made from synthetic materials, one must account for the fact that staple cloths provide a good retentivity of solid particles due to the short hairs on their surface. However, cake removal is often difficult from these cloths - more than from cloths of polyfilament and, especially, monofilament fibers. The type of fiber weave and pore size determine the degree of retentivity and permeability. The objective of the process, and the properties of particles, suspension and cake should be accounted for. The cloth selected in this maimer should be confirmed or corrected by laboratory tests. Such tests can be performed on a single filter. These tests, however, provide no information on progressive pore plugging and cloth wear. However, they do provide indications of expected filtrate pureness, capacity and final cake wetness. 

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