1911 Encyclopædia Britannica/Hydrolysis

HYDROLYSIS (Gr. ὕδωρ, water, λύειν, to loosen), in chemistry, a decomposition brought about by water after the manner shown in the equation R·X + H·OH = R·H + X·OH. Modern research has proved that such reactions are not occasioned by water acting as H₂O, but really by its ions (hydrions and hydroxidions), for the velocity is proportional (in accordance with the law of chemical mass action) to the concentration of these ions. This fact explains the so-called “catalytic” action of acids and bases in decomposing such compounds as the esters. The term “saponification” (Lat. sapo, soap) has the same meaning, but it is more properly restricted to the hydrolysis of the fats, i.e. glyceryl esters of organic acids, into glycerin and a soap (see Chemical Action).