Foundations of Chemistry最新文献

Are acids natural kinds? Or are they merely relevant kinds? Although acidity has been one of the oldest and most important concepts in chemistry, surprisingly little ink has been spilled on the natural kind question. I approach the question from the perspective of microstructural essentialism. After explaining why both Brønsted acids and Lewis acids are considered functional kinds, I address the challenges of multiple realization and multiple determination. Contra Manafu and Hendry, I argue that the stereotypical properties of acids are not multiply realized. Instead, given the equivalence between the proton-donating and electron-accepting mechanisms of Brønsted and Lewis, respectively, I show that acidity as a property type can be identified with a unique microstructural property, namely the presence of a LUMO or other low energy empty orbital. In doing so, I defend the view that the Lewis theory encompasses Brønsted–Lowry, and that all Brønsted acids are also Lewis acids. Contra Hacking and Chang, I thus maintain that the different concepts of acidity do not crosscut, and that the hierarchy requirement is met. Finally, by characterizing natural kinds as powerful objects and by adopting a dispositional view of functions, I illustrate how the microessentialist can make sense of the latent and relational character of most acids. In sum, I contend that acids are genuine natural kinds, even for the microstructural essentialist.

In this short essay I address the central topic of the Centenary Workshop on Acidity, that is the relations of the classical protonist acid–base theory by Brønsted and the electronist approach by Lewis. Emphasis is laid on the empirical background of both approaches and the over-theoretization of chemical phenomena (essentialism) is criticized.

Among the many acid-base concepts, the theory of Usanovich is one of the least known despite the most general scope including almost all chemical reaction types and even redox chemistry. Published 1939 in a Soviet journal in Russian language, it gained little immediate attention, and was later criticized mainly as being too broad in scope. Although several articles recently remembered Usanovich and his acid–base theory, one major inconsistency again was overseen: the electron is put in a row along with anions. Chemical history probably correctly puts this concept aside, also because it added little explanation capabilities beyond the elaborated considerations of the simultaneously published acid–base theory of Gilbert N. Lewis which was later refined by Pearson (hard and soft acids and bases, “HSAB”). A modified version of the core of Usanovich' concept is finally discussed. It combines the classic protic and aprotic acid–base concepts on the foundations of Lewis’ and Pearsons ideas.

Acidic substances were known for thousands of years, and their macroscopic-sensory characteristics were reflected by words in most ancient languages. In the Western canon, the history of the concept of acidity goes back to Ancient Greece. In Greek, the word associated with acidity from its early literary references was ὀξύς (“sharp”), and still in contemporary Greek the words “sour” and “acidic” have the same root. This paper makes a short presentation of the appearance of the abstract concept in the works of Plato and Aristotle and relates it, on one side to the already existing theological-philosophical tradition, starting with Hesiod´s Theogony and on the other, to the then available to the Greeks organoleptic experiences of sourness-vinegar and sour milk.

This work describes the concept of bond order. It shows that covalent bond energy is correlated to bond order. Simple expressions which included bond order are introduced to calculate bond energies of homo-nuclear and hetero-nuclear bonds. Calculated values of bond energies are compared with literature values and show there is very good agreement between and calculated and experimental values in the vast majority of cases. Bond order reveals the strength of a bond and shows the number of bonds in both homo-nuclear and hetero-nuclear covalent bonds.

We argue for an account of chemical reactivities as chancy propensities, in accordance with the ‘complex nexus of chance’ defended by one of us in the past. Reactivities are typically quantified as proportions, and an expression such as “A + B → C” does not entail that under the right conditions some given amounts of A and B react to give the mass of C that theoretically corresponds to the stoichiometry of the reaction. Instead, what is produced is a fraction α < 1 of this theoretical amount, and the corresponding percentage is usually known as the yield, which expresses the relative preponderance of its reaction. This is then routinely tested in a laboratory against the observed actual yields for the different reactions. Thus, on our account, reactivities ambiguously refer to three quantities at once. They first refer to the underlying propensities effectively acting in the reaction mechanisms, which in ‘chemical chemistry’ (Schummer in Hyle 4:129–162, 1998) are commonly represented by means of Lewis structures. Besides, reactivities represent the probabilities that these propensities give rise to, for any amount of the reactants to combine as prescribed. This last notion is hence best understood as a single case chance and corresponds to a theoretical stoichiometric yield. Finally, reactivities represent the actual yields observed in experimental runs, which account for and provide the requisite evidence for/against both the mechanisms and single case chances ascribed.

I put forward an inferentialist account of Lewis structures (LSs). In this view, the role of LSs is not to realistically depict molecules, but instead to allow surrogate reasoning and inference in chemistry. I also show that the usage of LSs is a central part of a person’s identity as a chemist, as it is defined within educational identity theory. Taking these conclusions together, I argue that the inferentialist approach to LSs and chemistry identity theory can be studied in parallel, as two complementary sides of the same research programme.

Kripke-Putnam argument for natural kind essentialism can be said to depend on placeholder essentialist intuitions. But some argue that such philosophical intuitions are merely preschooler cognitive biases which are not supported by scientific knowledge of natural kinds. Chemical substances, for instance, whether elements or compounds do not have such privileged set of underlying properties (‘same substance’ relation) which are present in all members of the kind and which provide necessary and sufficient condition for kind membership. In this paper, I argue that placeholder essentialism works for at least some of the scientific natural kinds especially for the basic chemical natural kind, i.e., element. I argue that the dual sense of the element (the basic substance and the simple substance) along with microstructuralism helps explain the essence of an element not only at the abstract level but also at the more concrete level. Based on this essentialist account of element, I conclude that placeholder essentialism is not completely without merit, and it fits nicely with at least some of our scientific natural kinds.