A method for making a number (N) of samples react under the same reaction conditions that includes heating a number of reaction containers simultaneously and maintaining the reaction containers at a predetermined temperature; placing a sample in each heated reaction chamber and maintaining a two-phase solution at a predetermined temperature; stirring the sample that is heated to the predetermined temperature to create a uniform solution, which is maintained for a predetermined time; and cooling the uniform solution without cooling the reaction container after the predetermined period of time has passed so as to gain a two-phase solution within the reaction container, where the samples have a solution where the phase state of a reaction solvent changes in a reversible manner between a two-phase solution state and a uniform solution state when the temperature fluctuates over or under a certain constant temperature.