The pH values are taken experimentally before and after adding NaoH and the surfactant. The values of pH are needed to be studied over a period of time, to keep a check on stability. Hence, the pH values are taken experimentally after a gap of fifteen days in three sets (Day1, Day 15 and Day 30). The values were plotted against time over a time of thirty days and values were observed to be close enough to declare that the nanofluid is stable. The pH values are plotted with time and temperature and is shown in Figure 4 .