in Chemistry, usually signifies the diffusion or separation of the constituent parts of bodies.—It differs from mere mechanical division; for when a body is chemically decomposed, the parts into which it is resolved are essentially different from the body itself; and though a mechanical force be applied to it ever so long, or with ever so much violence, the minutest 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 mass; but if sulphuric acid be applied, a decomposition takes place, and one of the component parts of the nitre, namely the nitric acid, rises in the form of fumes, which never could have been suspected to lie hid in the mild neutral salt.