Ionic equilibrium is the chemistry associated with salts, acids, and bases. The main application lies in environment science, especially the field of water chemistry. An example of ionic equilibrium studies in would be the examination of environmental damages caused to the Alaskan waters by the Exxon Valdez oil spill (a project to which Dr. Butler has close ties). In 1964, Dr. Butler developed a simple yet powerful method of performing equilibrium calculations in the classic Addison-Wesley book, Solubility and pH Calculations. At that time, chemists utilized slide rules and graph paper to figure and plot these equations. This updated version is expanded to include new advances in the field and to incorporate the use of the personal computer into this branch of chemistry.