Experimental results of antisolvent crystallization of ammonium dihydrogen phosphate from their aqueous solutions saturated at 30 degrees C by addition of methanol at preselected feeding rate R-A, studied by in situ measurements of laser beam intensity I transmitted through solutions and their temperature T as functions of feeding time t for methanol at rate R-A, are described and discussed. It was found that (1) measurement of temperature of solutions during antisolvent feeding is more informative and is more reliable than transmitted laser beam intensity measurements, (2) there are two regions of methanol feeding durations involving endothermic reactions and one region involving exothermic reactions, (3) the data of metastable zone width determined from the values of maximum antisolvent content Delta x(max) calculated from methanol feeding duration are reliable when the temperature difference Delta T=T-s-T-w, where T-s and T-w are temperatures of solution and water, respectively, for theoretical analysis, (4) rates Delta T/Delta t of linear changes in temperatures of solution and water with methanol feeding time t increases with feeding rate R-A, and (5) the maximum changes Delta T-max in the temperature of solution and water are related to antisolvent content Delta x associated with their appearance. It is argued that feeding of antisolvent methanol to saturated solutions or water leads to chemical reactions with evolution of heat. (C) 2016 Elsevier B.V. All rights reserved.