Is the glass half empty or half full? Is the glass half empty or half full? "Is the glass half empty or half full?" is a common expression, a proverbial phrase, generally used rhetorically to indicate that a particular situation could be a cause for optimism (half full) or pessimism (half empty), or as a general litmus test to simply determine an individual's worldview. The purpose of the question is to demonstrate that the situation may be seen in different ways depending on one's point of view and that there may be opportunity in the situation as well as trouble. Another perspective comes from psychology, where research has
Hammett acidity function HSO (18.4 M) has a "H" value of −12, and pyrosulfuric acid has "H" ~ −15. Take note that the Hammett acidity function clearly avoids water in its equation. It is a generalization of the pH scale—in a dilute aqueous solution (where B is HO), pH is very nearly equal to "H". By using a solvent-independent quantitative measure of acidity, the implications of the leveling effect are eliminated, and it becomes possible to directly compare the acidities of different substances (e.g. using p"K", HF is weaker than HCl or HSO in water but stronger than HCl in glacial acetic acid.)