Packings characteristics

Although native silicas have not been employed for SEC of biopolymers, and are also little used in SEC of polar synthetic polymers, it is worthwhile to survey those silicas which are parent materials for bonded SEC silica packings. The products 

SynChropak was the first commercial bonded silica of this type, followed by LIChrosorb DIOL and LiChrospher DIOL. Protein-Pak materials as well as Sl-Polyol are similar in surface composition. Recently a specifically pH-stabIIized, glycerol-bonded silica has been introduced on the market Zorbax Bio-Series 6F 250. The most popular are the TSK gel SW types which are thought to be bonded with a glycerol-ether moiety. On annealing from 400 to 823 K, the TSK gel SW 3000 showed a weight loss of ca. 15X while the carbon content was 7.3X, Indicating on oxygen-rich 

Trade name and grade Nominal pore dia-meter/nm FracticMi- ation range/ daltons Mean Oolumn dimensions particle length x i.d. (mm) size in /um bulk material - b.m. s=spherical a=angular 

Trade name and grade Nbminal pore dia-meter/nm Fraction-ation range/ daltons Mean particle size in /urn scspherical aeangular Oolumn dimensions length X i.d. (ran) bulk material = b.m. 

Sl )pliers Waters Associates, Milford, MA, USAi Shone Poulenc, France  

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Primary particles characteristics Packing characteristics Bulk properties... 

The experimentally determined packing factors are the only reliable values to use for design calculations although estimates can be made for packing shapes when no data are available. The packing characteristic is expressed as ... 

Figure 11.44 correlates the liquid and vapour flow rates, system physical properties and packing characteristics, with the gas mass flow-rate per unit cross-sectional area with lines of constant pressure drop as a parameter. 

More interesting data was found in the mixtures we have seen that carbon additives tend to reduce specific resistance of the mixture, while active material (activated carbon) increases resistance (54 10"3 ohm-m vs. 49 10"3 ohm-m). This phenomenon suggests that carbon-carbon component mixtures have better packing characteristics. 

R.M. German, Particle Packing Characteristics, Metal Powder Industries Federation, New York, 1989, p. 120. 

The measurement of effluent volume is not very reliable because of the effect of the geometry and packing characteristics of any column. It is often more useful to use a reduced parameter, such as V/V0, which is not so dependent upon column characteristics and is comparable with the calculation for RF values in thin-layer chromatography. 

It is possible to evaluate cohesive energies, packing characteristics and other properties of molecular crystals quantitatively on the basis of nonbonded interactions between atoms (Kitaigorodsky, 1973). The analytical expressions are of the form... 

Liquid holdup in liquid-liquid extractors must be defined for both the heavy and light phases. The light-phase outlet pressure is used to control the relative liquid holdup of the two phases. Higher light-phase outlet pressure increases the light-phase holdup. This pressure has been correlated with the phase density difference, rotor speed, and rotor dimensions (24). In addition, packing characteristics of volumetric surface area and porosity influence liquid holdup and throughout capability (23). 

Inability to describe packing characteristics as a simple mathematical function. 

An awareness of crystal packing characteristics and polymorphism helps one to understand incompatibility problems of different fats. Crystal formation has specific demands, and individual crystals in mixed systems each consists of only one species ofTAG. However, surfactants and other molecules can act as impurities and interrupt crystal growth. Different TAG are considered compatible when they co-crystallize as separate crystals under the same conditions without the formation of a eutectic. 

Abstract—Gas-liquid interfacial areas a and volumetric liquid-side mass-transfer coefficients kLa are experimentally determined in a high pressure trickle-bed reactor up to 3.2 MPa. Fast and slow absorption of carbon dioxide in aqueous and organic diethanolamine solutions are employed as model reactions for the evaluation of a and kLa at high pressure, and various liquid viscosities and packing characteristics. A simple model to estimate a and kLa for the low interaction regime in high pressure trickle-bed reactors is proposed. 

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