抄録
“Shigao (石膏)” is one of the Chinese mineral drugs, derived from calcium sulfate dihydrate (Gypsum, CaSO4・2H2O), which has been used as antipyretic for heat in the lung with high fever and dire thirst. In general, Japanese Kampo or Chinese medical doctors have made allowance for the amount of gypsum according to symptom complex of patients when they make decoctions of some formulations such as Byakko-ka-ninjin-to. However, the dissolution rate of gypsum with increasing amount was not clear. We extracted gypsum with hot water to measure the concentration of calcium using the atomic absorption spectrometry. The results showed that the calcium concentration was approximately 200 ppm when 10 g of block form of gypsum was used for one hour extraction and the dissolution rate was increased depending on the amount of gypsum and the length of extraction time. However, in the case of the powder form of gypsum, the calcium concentration was approximately 550 ppm for 15 min extraction and the dissolution rate was almost constant, independent of the amount of gypsum and extraction time. Thus, the block form of gypsum is better to use in order to be able to control the dissolution rate. Moreover, according to X-ray diffraction method and fluorescent X-ray analysis, the crystal structures and the contents of inorganic compounds were not changed before and after extraction, suggesting that the block form of gypsum has the possibility to be used several times.
