Critical Points and Scaling Laws for Finite Systems

We describe a new approach to the understanding of the thermodynamic properties of a physical system near a critical point. The critical point is characterized by the peculiar dependence of various quantities on the size of the system, rather than by the mathematical singularities which appear in an infinite system. We indicate a very general method of obtaining scaling laws for the critical behavior of any thermodynamic system by considering its thermodynamic fluctuations. As an example, a new scaling law is obtained for the susceptibility at a gas-liquid critical point.