1991 年 7 巻 5 号 p. 683-685
The melting of the eutectic compound of sodium chloride and water has been investigated in detail by differential scanning calorimetry and nuclear magnetic resonance. It has been found that the melting point of the eutectic compound of sodium chloride and water is -21.7°C, and not -22.3°C as it has been reported in the literature. The latter value is assigned to the melting of the oxygen adduct of the eutectic compound. The oxygen adduct is formed in salt solutions with concentrations below 0.2mol/l NaCl; the formation is maximal at around 0.1mol/l NaCl. The latter salt concentration is almost equal to that of the human blood and of the physiological saline water for mammals. It is referred to as the physiological salinity. These findings should have a fundamental connection with physicochemical and physiological problems in nature, and suggest that the physiological salinity plays a role of basic importance in biological systems. An interpretation for the findings is also presented.
