Graham's law has come to denote an important class of finely divided materials. Around the time Graham did his work, the concept of molecular weight was being established largely through the measurements of gases. Daniel Bernoulli suggested in 1738 in his book Hydrodynamica that heat increases in proportion to the velocity, and thus kinetic energy, of gas particles. Italian physicist Amedeo Avogadro also suggested in 1811 that equal volumes of different gases contain equal numbers of molecules. Thus, the relative molecular weights of two gases are equal to the ratio of weights of equal volumes of the gases. Avogadro's insight together with
Gay-Lussac's law which he was the first to formulate (c. 1808). He is also sometimes credited, rightfully according to many modern scholars, with being the first to publish convincing evidence that shows the relationship between the pressure and temperature of a fixed mass of gas kept at a constant volume."" These laws are also known variously as the Pressure Law or Amontons's law and Dalton's law respectively. The law of combining volumes states that, when gases react together to form other gases, and when all volumes are measured at the same temperature and pressure The ratio between the volumes of the reactant