Editing Acid–base reaction (section)

===Usanovich definition===
[[Mikhail Usanovich]] developed a general theory that does not restrict acidity to hydrogen-containing compounds, but his approach, published in 1938, was even more general than Lewis theory.<ref name=review1940/> Usanovich's theory can be summarized as defining an acid as anything that accepts negative species or donates positive ones, and a base as the reverse. This defined the concept of [[redox]] (oxidation-reduction) as a special case of acid–base reactions.

Some examples of Usanovich acid–base reactions include:
<math chem display=block>\begin{array}{ccccll}
  _\text{(base)} & & _\text{(acid)} \\[4pt]
  \ce{Na2O} &+& \ce{SO3} &\longrightarrow& \ce{2Na+ {} + \ SO4^2-} & \text{(species exchanged: } \ce{O^2-} \text{anion)} \\[4pt]
  \ce{3(NH4)2S} &+& \ce{Sb2S5} &\longrightarrow& \ce{6 NH4+ {} + \ 2 SbS4^3-} & \text{(species exchanged: } \ce{3 S^2-} \text{ anions)} \\[4pt]
  \ce{2Na} &+&  \ce{Cl2} &\longrightarrow& \ce{2 Na+ {} + \ 2 Cl-} & \text{(species exchanged: 2 electrons)}
\end{array}</math>