Theoretical principles

Aqueous solutions of alkali hypochlorites can be prepared under suitable operating conditions by the electrolysis of alkali chlorides in an electrolyzer without a diaphragm. 

When electrolyzing an aqueous solution of alkali chloride, hydrogen ions formed bv the dissociation of water are discharged at the cathode  

Apart from this main reaction, there may occur a reduction of hypochlorite ions at the cathode  

In this reaction, which is responsible for the losses of active chlorine and a lowering of current efficiency, the hypochlorite acts as a depolarizer of the hydrogen evolution. 

An access of CIO ions to the cathode is substantially hindered by the addition of a small amount of alkali chromate in the electrolyte. The presence of this compound lowers the loss of hypochlorite (due to the reduction of the latter) from some 30 per cent to 0.5—1 per cent. This favourable effect of the chromate is ascribed to its reduction at the cathode and formation of insoluble lower oxides CrO(OH), or Cr(0H)Cr04 which envelop the entire cathode in form of a film  

Because the resistance depends on the type of conductor, the resistivity p is defined as a material-specific quantity as follows  

The electric conductivity x with unit S cm represents the reciprocal of the resistivity. 

The electric conductivity of electrolytes strongly depends on concentration. To compare the conducting power of different electrolyte solutions, the electric conductivity is divided by the equivalent concentration, Cev. yielding the equivalent conductance, A (S cm val )  

When two electrodes immersed in an electrolyte solution are connected to a power supply, an electric field of strength E is created between them. In this field, a directed mass transport occurs. Anions drift to the positive pole while cations drift to the negative pole. Because the ion velocity, v, is strictly proportional to the electric field strength, the mobility of ions, u (cm V s ), is an independent characteristic  

In a strong electrolyte, cations and anions are present in the solution in the con-centration c+ and c, respectively. The following applies  

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In this article, we are contented to quote only the theoretical principle, the development and the implantation will make the object of future works. 

This section describes tire application of tire theoretical principles described above to specific stmctures and processes of current interest in electron transfer research. 

The book opens with a chapter on the theory underlying the technique of the chief operations of practical organic chemistry it is considered that a proper understanding of these operations cannot be achieved without a knowledge of the appropriate theoretical principles. Chapter II is devoted to a detailed discussion of experimental technique the inclusion of this subject in one chapter leads to economy of space, par ticularly in the description of advanced preparations. It is not expected that the student will employ even the major proportion of the operations described, but a knowledge of their existence is thought desirable for the advanced student so that he may apply them when occasion demands. 

This chapter is in no way meant to impart a thorough understanding of the theoretical principles on which computational techniques are based. There are many texts available on these subjects, a selection of which are listed in the bibliography. This book assumes that the reader is a chemist and has already taken introductory courses outlining these fundamental principles. This chapter presents the notation and terminology that will be used in the rest of the book. It will also serve as a reminder of a few key points of the theory upon which computation chemistry is based. 

The term ah initio is Latin for from the beginning. This name is given to computations that are derived directly from theoretical principles with no inclusion of experimental data. This is an approximate quantum mechanical calculation. The approximations made are usually mathematical approximations, such as using a simpler functional form for a function or finding an approximate solution to a dilferential equation. 

Structure-property relationships are qualitative or quantitative empirically defined relationships between molecular structure and observed properties. In some cases, this may seem to duplicate statistical mechanical or quantum mechanical results. However, structure-property relationships need not be based on any rigorous theoretical principles. 

A vast amount of research has been undertaken on adsorption phenomena and the nature of solid surfaces over the fifteen years since the first edition was published, but for the most part this work has resulted in the refinement of existing theoretical principles and experimental procedures rather than in the formulation of entirely new concepts. In spite of the acknowledged weakness of its theoretical foundations, the Brunauer-Emmett-Teller (BET) method still remains the most widely used procedure for the determination of surface area similarly, methods based on the Kelvin equation are still generally applied for the computation of mesopore size distribution from gas adsorption data. However, the more recent studies, especially those carried out on well defined surfaces, have led to a clearer understanding of the scope and limitations of these methods furthermore, the growing awareness of the importance of molecular sieve carbons and zeolites has generated considerable interest in the properties of microporous solids and the mechanism of micropore filling. 

A model describing a system s response that has a theoretical basis and can be derived from theoretical principles. 

A parallel but more historically comprehensive discussion of glass stmcture and composition has been given (36). Prediction of stmctural parameters and consequent properties from theoretical principles has increased with the advent of supercomputers. Of particular interest to glass scientists... 

Other types of inertial collectors which might be used for particulate separation from a carrying gas stream depend on the same theoretical principles developed for cyclones. Table 29-2 summarizes the effect of the common variables on inertial collector performance. 

In some cases, the ventilation process in the room can be simplified and mechanisms of air and contaminant movement under the influence of each of the above factors can be described using simplified theoretical principles of fluid mechanics, empirical data, and observations from numerous research studies. In general, the ventilation process in a room is complex and different factors have a joint effect on airflow patterns and characteristics, in continued spaces and in industrial buildings particularly. 

The user must have experience in thermal analysis and HVAC dimensioning and be familiar with the theoretical principles and details upon which such analysis is based in the program used. Engineering judgment will have to be used for tbe definition of the input parameters. 

The theoretical principles of attenuation have been considered in Section 10.1, but some illustrations are appropriate here. Figure 10.27 shows typical... 

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