The Effect of Impurities on Thermol Properties of Hydrate Gypsum Yang Huixian;Ding YonggangWith the help of DTA and with the various gypsum resources in our country, the effects of SiO_2 (both crystals and noncrystals),CaCO_3, Al_2O_3, and Al_2O_3·2SiO_2·2H_2O on the thermol properties of hydrate gypsum are studied. At the same time, the change of dehydrated enthalpy of hydrate gypsum which contain the impurities mentioned above was also measured. the research shows that the impurities in hydrate gypsum would change the thermol properties of hydrate gypsum,reduce the dehydrated temperature and increase dehydrated rate of hydrate gypsum. The reason for this is that the detydrated enthalpy of crystal water in the hydrate gypsum is reduced.Hydrate gypsum;;Impurity;;Dehydrated enthalpy