An adsorption isotherm log log p = C+n log v was developed and applied earlier. The isotherm has been used to determine the structural parameters of adsorbents. The application of the isotherm has been extended to determine separation factor of mixture of gases, surface area of adsorbed monolayer from energy consideration, categorisation of micropores etc. It is shown that equation of Lewis et al. for partial adsorption and equation of Langmuir can be deduced from isotherm equation of John. Advantages of John's isotherm are enumerated.