Electrostatic field high intensities

The intrazeolite cations necessary to balance the negative charge on the framework aluminum atoms are poorly shielded and as a result high electric (electrostatic) fields on the order of 1-10 V/nm are found in their vicinity. The magnitudes of the electric fields can be calculated from measured effects on the vibrational frequencies or intensities of IR bands of small diatomics such as CO or N2.24 They can also be determined from difference electron density maps determined by X-ray diffraction methods.25 These high electric fields can dramatically influence the stabilities of transition states with significant charge separations. 

An assemblage of even lightly charged particles can result in very high electrostatic field intensities at the surface of the assemblage. It is readily shown that for a volume of unipolar and uniformly distributed charged particles bounded by a surface equidistant from a center of symmetry, the... 

Table VII gives both the electrostatic field intensity and force due to a point charge corresponding to one electron in magnitude. It is apparent from these values that elementary point charges do not exert significant forces upon each other until the distance between them approaches molecular dimensions. At this point, field intensities become so high that electron transfer or tunneling must occur for the case where the point charges are of opposite sign.

The tablets (diameter 30 mm, thickness 1 nun) of frozen (at 265-260 K) adsorbent samples at water content Chjo=70.2 and 84.4 wt% were polarized by the electrostatic field at the intensity Fp=0.14-0.2 MV/m at 260 K and then cooled to 90 K with the field still applied and heated without the field at a heating rate p=0.05 K/s. The TSDC thermograms of hydrated LiChrolut EN adsorbent (Figure 5.31) are unusual because the depolarization or discharge current is observed at low temperatures T<220 K, and the direct current (dc) relaxation is absent at relatively high hydration h=236 and 5.4 g of water per gram of dry adsorbent. 

Penicillin extraction is an example of the application of process enhancanent via electrostatic fields. Solvent extraction as a means of recovery and purification of penicillin-G and a number of other antibiotics is well-established for these products. Use of liquid-liquid extraction involves operation at close to ambient tanper-ature and equipment-intensive processes such as precipitation and oystallization can be kept to a minimum. The high selectivity offered by chanicaUy suitable solvents has furthered the exploitation of extraction as a recovery ronte. In the case of penicillin-G (pen-G), extraction into a number of solvents is well known and these include n-butyl acetate, amyl acetate, chloroform, and methyl iso-bntyl ketone. 

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