in chemistry, usually signifies the diffusion or separation of the constituent parts of bodies.—It differs from mere mechanical division, in that when a body is chemically decomposed, the parts into which it is resolved are essentially different from the body itself; but though a mechanical force is applied to it ever so long, or with ever so much violence, the minute particles into which the body may be reduced, still retain their original nature.—Thus, for example, though we suppose nitre, or any other salt, to be reduced to ever so fine powder, each particle retains the nature of nitre, as much as the largest unpounded nails; but if oil of vitriol is applied, a decomposition takes place, and one of the component parts of the nitre rises in the form of a smoking acid spirit, which never could have been suspected to lie hid in the mild neutral salt.