Acid–base reaction liquid ammonia are similar to the reactions in water: Nitric acid can be a base in liquid sulfuric acid: The unique strength of this definition shows in describing the reactions in aprotic solvents; for example, in liquid : Because the solvent system definition depends on the solute as well as on the solvent itself, a particular solute can be either an acid or a base depending on the choice of the solvent: is a strong acid in water, a weak acid in acetic acid, and a weak base in fluorosulfonic acid; this characteristic of the theory has been seen as
Acid test (gold) or definitive tests to other materials, became popular during and after the California Gold Rush, but was current before then, as shown by this quote from the Wisconsin paper "The Columbia Reporter", November 1845: "Twenty-four years of service demonstrates his ability "to stand the acid test", as Gibson’s Soap Polish has done for over thirty years." Other examples of the figurative use of the phrase are the web sites Acid1, Acid2 and Acid3, which are designed to test web browsers for compliance with current web standards. Another example is the quick ratio method, nicknamed "acid test", used by financial analysts