base
/ BAYSS /
Rub a drop of soap or baking-soda paste between your fingers and notice the slippery, slightly soapy feel — and that faintly bitter taste if a little reaches your tongue. That slick, bitter character is the everyday signature of a base, the chemical opposite of an acid.
A base is a substance that accepts hydrogen ions (protons) — or, in the most familiar case, releases hydroxide ions (OH-) when it dissolves in water. Either way, a base removes the excess H+ that an acid would supply, pulling a solution toward the basic (alkaline) side. Common bases include lye, ammonia, lime, and the bicarbonate that neutralizes stomach acid in antacids.
Bases matter because they are the counterweight that lets us control acidity: they make soap, soften water, raise soil pH, and cancel acids in a reaction called neutralization. Note that base and alkali overlap but are not identical — alkali usually means a base that dissolves well in water, like sodium hydroxide, while base is the wider family.
Antacid tablets contain a base such as magnesium hydroxide; swallowed, it accepts protons from excess stomach acid and soothes heartburn.
A base accepts protons (or supplies hydroxide), opposing an acid.
Never taste an unknown base to test for bitterness or slipperiness — strong bases like lye burn skin and eyes as severely as strong acids, and the slippery feel is partly your own skin being dissolved.