base (redirected from ointment base)

base: see acids and bases.

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base

In chemistry, any substance that in water solution is slippery to the touch, tastes bitter, changes the colour of acid-base indicators (e.g., litmus paper), reacts with acids to form salts, and promotes certain chemical reactions (e.g., base catalysis). Examples of bases are the hydroxides of the alkali metals and alkaline earth metals (sodium, calcium, etc.; see caustic soda) and the water solutions of ammonia or its derivatives (amines). Such substances produce hydroxide ions (OH⁻) in water solutions. Broader definitions of bases cover situations in which water is not present. See also acid-base theory; alkali; nucleophile.

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(1) A starting or reference point.

(2) In a bipolar transistor, the elements that act as a switch. In NMOS and PMOS transistors, which make up CMOS circuits, the base is called the "gate." See transistor.

(3) A multiplier in a numbering system. In a decimal system, each digit position is worth 10x the position to its right. In binary, each digit position is worth 2x the position to its right.

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(mathematics)

base - radix.