Cady-Elsey

This definition is principally concerned with ionic solvents. A few important organic species may be synthesised in the superacid solvents to which this definition has most application. 

In this definition an acid is defined as a species that raises the concentration of the cation of the solvent, while a base raises the concentration of the anion of the solvent. This definition is of use when dealing with autolytic solvents such as liquid ammonia. Write down the autolytic reaction of ammonia, and so identify the solvent anion and cation. 

The anion is an amide ion, while the cation is an ammonium ion. Suggest what would be an acid in this solvent. 

Ammonium chloride would be an acid as it would raise the concentration of the cation, namely the ammonium ion. Now suggest what would act as a base in this solvent. 

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This theory is associated in its early protonic form with Franklin (1905, 1924). Later it was extended by Germaim (1925a,b) and then by Cady Elsey (1922,1928) to a more general form to include aprotic solvents. Cady Elsey describe an acid as a solute that, either by direct dissociation or by reaction with an ionizing solvent, increases the concentration of the solvent cation. In a similar fashion, a base increases the concentration of the solvent anion. Cady Elsey, in order to emphasize the importance of the solvent, modified the above defining equation to ... 

The various acid-base definitions are summarized in the Venn diagram (Fig. 2.1). From this it can be seen that the Usanovich definition subsumes the Lewis definition, which in turn subsumes all other definitions (i.e. Arrhenius, Bronsted-Lowry, Germann-Cady-Elsey, Lux-Flood). 

Also shown is how the topic of AB cements relates to these definitions. An ideal definition for a subject should be one that exactly fits it. It should cover all aspects of the subject while excluding all extraneous topics. Thus, a theory should be neither too restrictive nor too general. The Arrhenius and Germann-Cady-Elsey definitions do not relate to the subject at all as... 

Bata obtaaned by Estreicher (Zeitsch. physihd. Chem., 1899, 31, 176) and corrected by Antropoff Cady, Elsey, and Berger (J. Amer. Ohm. Soc., 1922, 44, 1456) give the solubility of helium in water betweenJl0 and 30° C., but find no minimum value. 

Acid Usually either a proton donor (Bronsted-Lowry definition) or an electron pair acceptor (Lewis definition), but there are other definitions, such as Arrhenius and Cady-Elsey. 

Cady, H. P. Elsey, H. M. (1922). A general conception of acids, bases and salts. Science, 56, 27 (Lecture abstract). 

Cady and Elsey gave the so-called solvent-system definitions, which depend on the mode of self-ionization of the particular solvent. Each solvent is considered as a parent of acids and bases. A solvo-acid is defined as a solute which increases the concentration of cations characteristic of the pure solvent and a solvo-base as a solute which increases that of the anions characteristic of the pure solvent ... 

Germann, Cady and Elsey, Jander, Wickert, and Smith have extended the solvent system theory of acids and bases to include non-protonic systems. Germann showed that aluminum chloride in phosgene has typical acid properties. The solution dissolves metals with evolution of carbon monoxide gas and is neutralized... 

Germann s definitions of acids and bases were simplified by Cady and Elsey, who defined an acid as a solute that gives rise to a cation characteristic of the solvent, and a base as a solute that gives rise to an anion characteristic of the solvent. 

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