Heat storage composition, latent heat storage capsules containing said heat-storage composition and temperature control apparatus using said capsules

A heat storage composition excellent in heat storing effect contains calcium chloride hexahydrate as the main component and an appropriate amount of a nucleating agent combination for inhibiting supercooling which is composed of barium sulfide, barium chloride dihydrate and strontium chloride hexahydrate or of barium chloride dihydrate and strontium chloride hexahydrate and optionally contains an appropriate amount of a thickening agent combination composed of an ultrafine silica powder and glycerin. Latent heat storage capsules contain the above heat storage composition and are improved particularly in their structure such that improved heat storage and release effects can be produced. A temperature control apparatus can make most of the heat storage capsules in the temperature control of a hothouse or the like.