2. (Chem.) One of a class of caustic bases, such as soda,
potash, ammonia, and lithia, whose distinguishing
peculiarities are solubility in alcohol and water, uniting
with oils and fats to form soap, neutralizing and forming
salts with acids, turning to brown several vegetable
yellows, and changing reddened litmus to blue.
{Fixed alkalies}, potash and soda.
{Vegetable alkalies}. Same as {Alkaloids}.
{Volatile alkali}, ammonia, so called in distinction from the
fixed alkalies.