IHP

IHP) (the Helmholtz condenser formula is used in connection with it), located at the surface of the layer of Stem adsorbed ions, and an outer Helmholtz plane (OHP), located on the plane of centers of the next layer of ions marking the beginning of the diffuse layer. These planes, marked IHP and OHP in Fig. V-3 are merely planes of average electrical property the actual local potentials, if they could be measured, must vary wildly between locations where there is an adsorbed ion and places where only water resides on the surface. For liquid surfaces, discussed in Section V-7C, the interface will not be smooth due to thermal waves (Section IV-3). Sweeney and co-workers applied gradient theory (see Chapter III) to model the electric double layer and interfacial tension of a hydrocarbon-aqueous electrolyte interface [27]. 

There is, or may be, an iimer layer of specifically adsorbed anions on the surface these anions have displaced one or more solvent molecules and have lost part of their iimer solvation sheath. An imaginary plane can be drawn tlirough the centres of these anions to fomi the inner Helmholtz plane (IHP). 

These calculations have, as their aim, the generation of an adsorption isotherm, relating the concentration of ions in the solution to the coverage in the IHP and the potential (or more usually the charge) on the electrode. No complete calculations have been carried out incorporating all the above temrs. In general, the analytical fomi for the isothemr is... 

Eigure 3 schematically depicts the stmcture of the electrode—solution interface. The inner Helmholtz plane (IHP) refers to the distance of closest approach of specifically adsorbed ions, generally anions to the electrode surface. In aqueous systems, water molecules adsorb onto the electrode surface. 

Electrically, the electrical double layer may be viewed as a capacitor with the charges separated by a distance of the order of molecular dimensions. The measured capacitance ranges from about two to several hundred microfarads per square centimeter depending on the stmcture of the double layer, the potential, and the composition of the electrode materials. Figure 4 illustrates the behavior of the capacitance and potential for a mercury electrode where the double layer capacitance is about 16 p.F/cm when cations occupy the OHP and about 38 p.F/cm when anions occupy the IHP. The behavior of other electrode materials is judged to be similar. 

Fig. 1. Schematic representation of the electrochemical or diffuse double layer showing the inner (IHP) and outer (OHP) Helmholtz planes and the...

Fig. 1. The structure of the electrical double layer where Q represents the solvent CD, specifically adsorbed anions 0, anions and (D, cations. The inner Helmholtz plane (IHP) is the center of specifically adsorbed ions. The outer Helmholtz plane (OHP) is the closest point of approach for solvated cations or molecules. O, the corresponding electric potential across the double layer, is also shown.

Tropinin Str. 49, Nizhny Novgorod, 603950, Russia E-mail krylov ihps.nnov.ru... 

Chemical Process Products Co., Inc., Bull. DC-11 and MTP-1 (4/94). Chemical Process Products Corp., Bull. IHP-1 (12/91). 

Norton Chemical Process Products, Intalox High Performance Separation Systems, Bulletin IHP-1, Norton Chemical Process Products Corporation (1987). 

Input engine power IHP (hp) required for a given pump theoretical output Qj and pump working pressure PWP is... 

TNF was originally identified because of its cytotoxic activity against some tumor cell lines and its ability to induce hemorrhagic necrosis of solid tumors in various animal models. However, the clinical use of TNF as an anticancer drug has been so far limited by its severe cardiovascular side effects. Therefore, TNF treatment is limited to regional and local administration of high doses of TNF, often in combination with chemotherapy, as accomplished in isolated limb and isolated hepatic perfusion (ILP and IHP, respectively) [5]. In the case of ILP, typically metastases are treated, patients benefit from this procedure by salvage of limbs from a loss by amputation. 

FIGURE 1-11 Schematic representation of the electrical double layer. IHP = inner Helmholtz plane OHP = outer Helmoltz plane. 

The inner layer (closest to the electrode), known as the inner Helmholtz plane (IHP), contains solvent molecules and specifically adsorbed ions (which are not hilly solvated). It is defined by the locus of points for the specifically adsorbed ions. The next layer, the outer Helmholtz plane (OHP), reflects the imaginary plane passing through the center of solvated ions at then closest approach to the surface. The solvated ions are nonspecifically adsorbed and are attracted to the surface by long-range coulombic forces. Both Helmholtz layers represent the compact layer. Such a compact layer of charges is strongly held by the electrode and can survive even when the electrode is pulled out of the solution. The Helmholtz model does not take into account the thermal motion of ions, which loosens them from the compact layer. 

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