Foundations of and challenges to electrolyte chemistryFoundations of Chemistry

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Authors
Kevin Charles de Berg
Year
2015
DOI
10.1007/s10698-015-9219-y
Subject
Chemistry (all) / History / Biochemistry

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Foundations of and challenges to electrolyte chemistry

Kevin Charles de Berg1  Springer Science+Business Media Dordrecht 2015

Abstract Mathematics is so common-place in modern physics and chemistry that one may not realise how controversial its admittance was to these fields in the eightieth and ninetieth centuries respectively. This paper deals with the controversy during the formation of physical chemistry as a discipline in the late ninetieth and early twentieth centuries and sketches more recent criticisms of the way mathematics has been used in solution chemistry. The controversy initially related particularly to electrolyte chemistry and its emerging use of mathematics to support Arrhenius’ theory of ionic dissociation. The impact of mathematics on the field is divided into three phases: that from 1880 to 1920 which was a period of heightened controversy; that from 1920 to 1990 which was a period of relative calm and mathematical development; and finally, that from 1990 to the present which has been a time of reflective criticism of the extensive use of empirical parameters in the emergent mathematics of the twentieth century. It is argued that the current solution to the criticism, as proposed by Heyrovska, is best viewed in the light of the historical development of the controversy.

Keywords Ionic dissociation  Ionists  Hydrationists  Thermodynamics  Mathematics 

Controversy  Physical chemistry

Introduction

Electrolytes, solutions that conduct electricity, are vital for a functioning human body, are an important component of many fertilisers, and have an important role in much of analytical chemistry. An understanding of the nature of aqueous solutions of salts, like the common salt sodium chloride, an example of an electrolyte, began in earnest from about & Kevin Charles de Berg kdeberg@avondale.edu.au 1 Avondale College of Higher Education, Cooranbong, NSW, Australia 123

Found Chem

DOI 10.1007/s10698-015-9219-y 1880 amidst considerable controversy. The controversy can be classified as one that existed between the ionists, who believed that a salt dissociated into its ions when dissolved in water, and the hydrationists, who believed that the dissolution of a salt in water involved the association of salt molecules with water (de Berg 2006a). Among the chief ionists were the Swedish chemist Svante Arrhenius (1859–1927), the Dutch chemist Jacobus van’t Hoff (1852–1911), and the German chemist Wilhelm Ostwald (1853–1932). The dominant hydrationists were the English chemists Henry Armstrong (1848–1937) and Spencer

Pickering (1858–1920), and the Irish physicist/chemist George Fitzgerald (1851–1901).

The initial controversy lasted from about 1880–1920 by which time it could be said that the ionists had gained the upper hand even though a full and satisfying description of electrolytes had not been reached. A partial reason for the emerging dominance of the ionists related to the fact that dilute solutions of weak electrolytes, those that were poor conductors of electricity, had been well-characterised by the Ostwald dilution law which was obtained by applying Guldberg and Waag’s equilibrium law to the partial dissociation equation associated with Arrhenius’ principle of ionic dissociation. This was followed by about 70 years of relative calm during which time the problem of describing strong electrolytes, those that were good conductors of electricity, and more concentrated solutions of electrolytes was addressed by Gilbert Lewis (1875–1946), Merle Randall (1888–1950), Peter Debye (1884–1966), Erich Huckel (1895–1980), Lars Onsager (1903–1976), and more recently by Kenneth Pitzer (1914–1997). The chemists of this era assumed strong electrolytes were totally dissociated into their ions and that the problem of concentrated solutions could be addressed through the introduction of concepts like activity, activity coefficient, and ionic strength to account for the impact of ionic interactions.

By 1990 increasingly elaborate mathematical equations containing increasing numbers of empirical correction factors were being used for describing concentrated solutions of strong electrolytes.

Around 1990 criticisms of the use of such elaborate equations began to appear in the chemistry literature (Darvell and Leung 1991; Franks 1991) partly because of the fact that these equations lacked physical significance. The correction factors designed to bring theory into line with experiment were regarded as simply fudge factors. Heyrovska (1991) responded to the criticism by claiming that a full physical description of concentrated solutions of strong electrolytes was now available and was best achieved by returning to

Arrhenius’ original use of partial dissociation and the hydrationists’ emphasis on hydration in aqueous solutions, albeit hydration which included that of ions rather than hydration of undissociated molecules exclusively. This paper describes the growth of chemical knowledge over these three periods; 1880–1920, 1920–1990, 1990-current; of electrolyte chemistry amidst controversy and challenge. It is argued that Heyrovska’s current modelling of electrolyte solutions is best understood from the point of view of the historical and philosophical issues that arose from 1880 to the beginning of the twenty-first century. A sketch of these three important periods now follows.

The controversy from 1880 to 1920

While details of the controversy have been described elsewhere (de Berg 2003; Dolby 1976), the focus in this paper will be on the issues surrounding the increasing dependence on mathematics within the emerging chemistry discipline of the twentieth century. It was in the period 1880–1920 that physical chemistry emerged as a discipline within chemistry

K. C. de Berg 123 with the first dedicated European journal, Zeitschrift fur Physikalische Chemie, being published from 1887, and the first dedicated American journal, Journal of Physical

Chemistry, being published from 1896. While Inorganic Chemistry and Organic Chemistry were largely descriptive chemistries over the period, Physical Chemistry paralleled Physics as a discipline in many ways and characteristically relied on a mathematical approach to chemical theory and exegesis. It was this reliance on mathematics within a discipline that was historically heavily descriptive and experimental that proved objectionable to chemists such as Henry Armstrong. Gingras (2001) observed a similar reaction of mainstream physicists to Newton’s mathematical approach to gravity over a century earlier.