Historical sense

The term aromatic will be used in a strict non-historical sense to mean possessing a cyclic 7r-electron system (6 and 10 electrons for the mono- and bi-cyclic rings discussed in this review). Heteroaromatic compounds, like carboaromatics, have widely different degrees and types of electronic dissymmetry and polarizabihty. Consequently, their reactivity varies tremendously with any one reagent and their relative reactivity changes drastically with the type of reagent. In this sense, aromatic compounds show differences in reactivity but not in aromaticity. The virtues of this qiuilitative concept of aromaticity and the pitfalls of trying to use it as a quantitative concept in modern context have been ably presented by Peters and by Balaban and Simon. ... 

In terms of layout, it might be preferable from a historic sense to start with quantum theories and then develop classical theories as an approximation to the more rigorous formulation. However, I think it is more pedagogically straightforward (and far easier on the student) to begin with classical models, which are in the widest use by experimentalists and tend to feel very intuitive to the modern chemist, and move from there to increasingly more complex theories. In that same vein, early emphasis will be on single-molecule (gas-phase) calculations followed by a discussion of extensions to include condensed-phase effects. While the book focuses primarily on the calculation of equilibrium properties, excited states and reaction dynamics arc dealt with as advanced subjects in later chapters. 

For the following limited discussion of ions in water it is advisable to define class (a) and class (b) in the earliest historical sense. Class (a) metal ions form halides whose stability in water is of the order MFn > MCln > MBrn > MI . Class (b) metal ions form halides whose stability is in the reverse order. Table I classifies metal ions in this way. This definition clearly leaves out of consideration (on experimental grounds) acceptor properties, especially of neutral species, which could not be studied in this way and to which we return later. We now need some quantitative experimental assessment of the degree of class (a) or (b) character. For simplicity we shall use —AG°aq/per ligand for the first group of more or... 

In a classical sense, vitamin D3. the form produced in animals, is not a true vitamin" because it is produced in the skin from 7-dehydrochole.sterol by UV radiation in the range of 290 to 3(X) nm. 7-Dehydrocholesterol is produced from cholesterol metabolism. Only when exposure to sunlight is inadequate does vitamin Di become a vitamin in the historical. sense. Further, vitamin D3 is now termed a provitamin because it requires hydroxylation by the liver and the kidney to be fully active. 

Finally, there is a historical sense of the notion of a law of nature. A dictum is a law of nature in this sense if, for whatever reason, it has been widely described and considered as such. It is even possible that such a law has never been widely accepted as a generalized statement of the best knowledge and belief in a certain area. In some ways this sense is trivial. The reason it must be separately introduced and considered is that some writers, both philosophers and scientists, have felt free to introduce a particular dictum as an example into a discussion of laws of nature, simply because it is widely known as "X s Law," without explicitly considering whether it qualifies in either of the other senses (Christie, 1994). 

The first issue, universal quantification, is a requirement that there be no exceptions to a law. It must be "in all cases" or "in no case." Even "in the vast majority of cases" will not do. The problem with this clause is an implicit ceteris paribus requirement for most laws (Cartwright, 1983). Newton s law of gravitation, for example, is a perfectly respectable law of nature in the epistemological and historical senses. It purports to quantify the force of interaction between a pair of massive objects. It has been empirically verified by measurement of the force between a pair of suspended metal spheres in a laboratory. But the law does not quantify the force, even as an approximation, if we take the trouble to provide the spheres with an electrostatic charge. 

Literature concerning the food industries has its origins in biblical times and much of it, in a historical sense, is really part of the general literature of the particular period or era (with the exception of relatively more recent times) considered. Thus Roman history as such and the private lives of the Romans, in particular, have to be studied to gain some idea of the food industry of that period. Much of food literature of early times is inextricably woven into the pharmaceutical and medical history of those periods. 

These readers will need to keep in mind the special (now archaic) senses in which such terms as "atomicity," "diatomic," "equivalent," "rational formula," and "graphic formula" were used in the middle of the nineteenth century. These historical senses are explained in the text. 

In Saved (1965), revived with such energy and vision by Sean Holmes and with Bond s active engagement in the critically acclaimed 2011 Lyric Theatre production, we have one of the most iconic and defining British plays of the post-war period. The circumstances surrounding the play s first production have been well documented by previous writers and scholars (notably Browne, 1975, and Hay and Roberts, 1980). My intention is not therefore to re-enter that critical area in a narrowly socio-historical sense. As Lacey succinctly observes ... 

In a historical sense, the problem of which isomer of 2-butene was which was resolved, long before the spectroscopic techniques described here were widely avail-... 

Additional characteristics, related to reactivity differences between aromatic and nonaromatic compounds, which, in an historical sense, long preceded these observations, will be discussed subsequently. Although we will deal somewhat more extensively with the notation shortly, it is very important that you recall the use of the double-headed resonance arrow from Chapter 1. Note in particular now that all of the forms shown here are considered identical, and drawing any one of them is the same as drawing all of them or any other of them. 

In a historical sense, but one which continues, the expansion of the concept of an acid to nonprotonaceous materials has had important effects. These include the idea that the interactions between electron-rich species and those with empty orbitals might be described in terms of acids and bases and that equilibrium constants... 

I have read this work in manuscript and can assure the reader that the treatment of the subject is thorough, fully documented, and always sensitive to questions of human values. The subject itself is clearly defined and its scope delimited in the Preface. I do not mean to suggest that this is a narrow, highly specialized study, aimed at an audience of professionals only. On the contrary, I find that the author gives abundant proof that she has developed what T.S. Eliot called the historical sense in his essay Tradition and the Individual Talent ... 

The historical sense involves a perception, not only of the pastness of the past, but of its presence the historical sense compels a man to write not merely with his own generation in his bones, but with a feeling that the whole of the literature of Europe from Homer and within it the whole of the literature of his own country has a simultaneous existence and composes a simultaneous order... . 

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