Acid-base concepts history

W. B. Jensen, The Lewis Acid-Base Concepts An Overview, Wiley-Interscience, New York, 1980, and H. L Finston and Allen C. Rychtman, A New View of Current Acid-Base Theories, John Wiley Sons, New York, 1982, provide good overviews of the history of acid-base theories and critical discussions of the different theories. R. G. Pearson s Hard and Soft Acids and Bases, Dowden, Hutchinson, Ross, Stroudsburg, PA, 1973, is a review by one of the leading exponents of HSAB. For other viewpoints, the references provided in this chapter should be consulted. 

A history of acid-base theories was given by Jensen, W. B. The Lewis Acid-Base Concepts An Overview Wiley-Interscience New York, 1980. 

The history of the measurement of hydrogen-ion concentration parallels not only progress in understanding of the acid-base concept but also the development of suitable instrumentation for indication. This brief survey explores the early beginnings, the development of the potentiometer, standard cells, and null point devices. These led to the vacuum tube voltmeter and the design of the first commercial pH meter. 

Ideas about adds and bases (or alkalis) date back to ancient times. The word acid is derived from the Latin acidus (sour). Alkali (base) comes from the Arabic al-qali, referring to the ashes of certain plants from which alkaline substances can be extracted. The acid-base concept is a major theme in the history of chemistry. In this section, we emphasize the view proposed by Svante Arrhenius in 1884 but also introduce a more modern theory proposed in 1923 by Thomas Lowry and by Johannes Bronsted. 

So far, the emphasis has been on concept creation, roughly following the route of history. This brings us to around the eighteenth century. French chemist Nicolas Lemery (1645-1715) was born in Rouen and was one of the first scientists to develop theories on acid-base chemistry. By a theory, I mean a causal explanation that makes sense of all, or as much as possible, of the data that has been collected to date. The theory should be able to predict new information that can be collected and tested for compatibility. Earlier in this chapter I called this fertility . A theory of acidity should ej lain why all the members of the class of acids behave as they do and why the nonmembers do not. When chemists construct a theory, they may find that minor alterations are required. This is called accommodation and is felt to be natural in the development of a theory. If, however, there comes a point where accommodation cannot explain a large portion of the new evidence, a new explanation is created. This is called a paradigm shift and the topic of acidity offers examples of it that will be explored later. 

The exact verbal definition of qualitative concepts is more often the province of philosophy than of physical science. However, the various definitions suggested for acids and bases have been closely linked with the development of physical chemistry and have often served to stimulate experimental work and to further our understanding of chemical processes, and we shall therefore devote some time to this subject. The definitions used in the remainder of this book will be those proposed by Bronsted in 1923, namely, An acid is a species having a tendency to lose a proton, and a base is a species having a tendency to add on a proton. This can be represented schematically by A B-j-H", where A and B are termed a conjugate or corresponding) acid-base pair. Before examining the consequences of this definition and its relation to more recent concepts we shall consider briefly the previous history of the terms acid and base . 

Based on the practical history of scale-up, most fermentation processes for alcohol and organic acid production have followed the concepts of geometric similarity and constant power per unit volume. From the above concept, and as a strong basis for translation of process criteria, only physical properties of the process were considered in the scale-up calculation. For power consumption in an agitated vessel, there is a fixed relation between impeller speed, N, and impeller diameter, l)t. The constant power per unit volume, for a mechanical agitated vessel is given by ... 

Although acids and bases have been recognized since antiquity, our concepts of them are still the subject of debate and development (Walden, 1929 Hall, 1940 Bell, 1947, 1973 Luder, 1948 KolthofF, 1944 Bjerrum, 1951 Day Selbin, 1969 Jensen, 1978 Finston Rychtman, 1982). The history of these concepts is a long one and can be seen as a prolonged and continuous refinement of inexact and commonsense notions into precise scientific theories. It has been a long and difficult journey and one that is by no means ended. 

G. -M. Schwab History of Concepts in Catalysis. -J. Haber Crystallography of Catalyst Types. -G.Froment, L. Hasten Catalytic Kinetics Modelling. -A J. Lecloux Texture of Catalysts. - K Tanabe Solid Acid and Base Catalysts. 

I begin the topic with an approach based on readUy observable phenomena, as an attempt to carve out the concept of acidity from the landscape of chemical reactions. (There is a well established history of the topic that lends itself to such an approach, based on... 

Extractive separation of metals is usually based on complex formation with inorganic and organic ligands. Therefore the use of the ideas, approaches, and methods of coordination chemistry has always been a most fruitful approach to the extraction of the elements. History shows that many problems of selectivity of separation or enhanced isolation have been successively solved by the rational application of coordination chemistry, e.g., the concept of hard and soft acids and bases. The efficiency of extraction depends on, inter alia, the ratio of charge and coordination number of metal ion. Study of this effect permitted the development of ways to improve separation due to changes in hydration of the species to be extracted. 

The most common approach to surface modification with transition aluminas is through control of the thermal treatment. As shown in Figures 5 and 7, it is quite easy to alter the total surface Lewis and Bronsted acidity and basicity via control of the hydroxyl concentration. To some extent this technique has been used since the early 1950s, particularly in chromatographic aluminas. The so-called Brockmann scale for rating aluminas is based on thermal history, and commercial materials are available today in the various Brockmann grades. Only recently has the concept been applied to large scale adsorption systems. 

Describing the history of chemical bums from antiquity to today presents some difficulties. The first, and most important, rests on the recent concepts of acids and bases. 

It should be explained that at this stage in the history of chemistry the concept of atomic weight had only recently been introduced by John Dalton and nobody was quite sure about how it should be calculated. By contrast as early as the 1790s Richter had introduced the concept of equivalent weight that is the amount of one substance that reacts with a particular amount of another substance. Several chemists soon published lists of the equivalent weights of compounds, especially acids and bases which, as Richter had realized, reacted together in definite proportions in the course of neutralization reactions. 

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