History of chemistry 1808, certain of his central ideas were soon adopted by most chemists. However, uncertainty persisted for half a century about how atomic theory was to be configured and applied to concrete situations; chemists in different countries developed several different incompatible atomistic systems. A paper that suggested a way out of this difficult situation was published as early as 1811 by the Italian physicist Amedeo Avogadro (1776-1856), who hypothesized that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules, from which it followed that relative molecular weights of any two gases are the same as
Zeroth law of thermodynamics that provides a continuous ordering of states. The dimensionality of a surface of constant temperature is one less than the number of thermodynamic parameters, thus, for an ideal gas described with three thermodynamic parameters "P", "V" and "N", it is a two-dimensional surface. For example, if two systems of ideal gases are in equilibrium, then = where "P" is the pressure in the "i"th system, "V" is the volume, and "N" is the amount (in moles, or simply the number of atoms) of gas. The surface = constant defines surfaces of equal thermodynamic temperature, and one may label defining "T"