| 摘要 |
PROBLEM TO BE SOLVED: To obtain a refrigeration material which freezes in a home refrigerator without fail and the freezing of which is recognizable by putting a liquid which is a constant-temperature freezing material into a container at least a half of one side of which is transparent. SOLUTION: The constant-temperature freezing material completely freezes to become a white solid and has a latent heat of melting. In order to obtain a refrigeration material capable of freezing within 24 hr in a home refrigerator, it is preferable that an aqueous ammonium chloride solution in put in a container having a thermal conductivity of 0.2 W/m.K or higher. An aqueous ammonium chloride solution with a concentration of 1-3 mol% is preferable as a refrigeration material having an m.p. of -16 deg.C; and an aqueous potassium chloride solution with a concentration of 1.8-4 mol%, as a refrigeration material having an m.p. of -10 deg.C. Thus, a refrigeration material effctive for a long time can be obtained. At least a half of one side of the container is transparent, since a half of one side must be transparent in order to recognize the complete freezing of the material. Examples of a plastic having a thermal conductivity of 0.2 W/m.K or higher are polyethylene, nylon, polypropylene and polyurethane. The container preferably has a thickness of 1.5 mm or lower and a liquid- containing volume of 1 L or lower.
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