Steam digester Torricelli and further developed by German scientist Otto von Guericke with his Magdeburg hemispheres. Guerike's demonstration was documented by Gaspar Schott, in a book that was read by Robert Boyle. Boyle and his assistant Robert Hooke improved Guericke's air pump design and built their own. From this, through various experiments, they formulated what is called Boyle's law, which states that the volume of a body of an ideal gas is inversely proportional to its pressure. Soon the ideal gas law was formulated. Based on these concepts in 1679 a Boyle's associate, named Denis Papin, built a "bone digester", which is
Graham's law involve the movement of more than one gas. In the same conditions of temperature and pressure, the molar mass is proportional to the mass density. Therefore the rate of diffusion of different gases is inversely proportional to the square root of their mass densities. Let gas 1 be H and gas 2 be O. (This example is solving for the ratio between the rates of the two gases) Therefore, hydrogen molecules effuse four times faster than those of oxygen. Using the formula of gaseous diffusion, the ratio of rate of diffusion of NH and HCl gas was obtained practically as