Affinity, dualistic theory

For his doctoral dissertation Berzelius built a voltaic pile and studied the effects of galvanic current on patients. He found no effects (and gained no new patients), but this started a chain of thought that culminated 11 years later in a dualistic theory of chemical affinity. Berzelius followed up the experiments of Nicholson and Carlisle to find that not only did electricity split water, but it also split salts. Simultaneously with Davy, who we encounter shortly, he used electrolysis to isolate such alkaline earth metals as calcium and barium. He then proposed a dualistic theory of chemical affinity based on electrical attraction ... 

Acids and bases (our acidic and basic oxides) enter as such (purement et simplement) into the composition of neutral salts without any intermediary which serves to unite them, whilst metals, on the contrary, cannot combine with acids unless they have first been more or less oxidised. It can be said rigorously that metals are not soluble in acids, but only metallic oxides , the oxygen being taken from water or from the acid, and then this oxygen must have a greater affinity for the metal than for hydrogen or the acid radical, respectively. This was the basis of the later Dualistic Theory of Berzelius (seeVol. iSo. 

The dawn of the nineteenth century saw a drastic shift from the dominance of French chemistry to first English-, and, later, German-influenced chemistry. Lavoisier s dualistic views of chemical composition and his explanation of combustion and acidity were landmarks but hardly made chemistry an exact science. Chemistry remained in the nineteenth century basically qualitative in its nature. Despite the Newtonian dream of quantifying the forces of attraction between chemical substances and compiling a table of chemical affinity, no quantitative generalization emerged. It was Dalton s chemical atomic theory and the laws of chemical combination explained by it that made chemistry an exact science. 

It was then natural to assume further that the usual operation of elective affinity is itself electrostatic, the attraction of oppositely charged atoms of different species. Davy in England, and Jons Berzelius in Sweden, both soon came to this view, and the latter formulated an electrochemical theory of the formation of compounds, published in 1814, which put forward this dualistic hypothesis in explanation of all chemical action. Berzelius even extended these ideas into organic chemistry, proposing that groups of atoms can form compound radicals , positive and negative, which then join together as elements would. 

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