On chemical dynamics and statics under the action of light
Since the second half of the last century chemical statics and dynamics have developed into a veritable science of their own. The general law governing velocity of chemical reaction and chemical equilibrium in homogeneous systems is now known as the law of action of mass; the law governing velocity of physical or molecular transformations in heterogeneous systems proves also to be of a general and simple nature: the velocity is directly proportional to the surface of contact of the reacting parts and to the remoteness of the system from the point of equilibrium;! the velocity of chemical reaction in heterogeneous systems and chemical equilibrium in heterogeneous systems represent no phenomena sui generis , and the laws governing them are only combinations of the other two laws mentioned.