Abstract:

Through the analysis of the methylene blue agent in differential thermal balance,the author in this paper observes that below 121℃ the dehydration process of both absorbed water and crystal water in the agent are carried out in two steps,and above 121℃ there occurs the degradation of the thermal oxidation.After a comparative study of four temperatures in dehydration,the author further suggests that the constant weight of the sample in 120±3℃ is an ideal condition to produce waterless methylene blue,and the thermo-analysis curve is the basis to direetly determine the moisture content of the sample.The method is simple and convenient，with a good reapearance and a relatively quiek and accurate elimination of the disturbance of the thermaloxidation. The author also diseusses the calibration of the formula for API balance sample.

Key words: Dehydration, Methylene blue, Thermal analysis, Moiusture content, oxidation, Degradation