Abstract: The heat accumulating material provided according to this invention makes use of the latent heat of fusion of sodium acetate trihydrate, and it comprises, as blended in a system consisting of sodium acetate and water, at least one nucleation catalyst selected from the group of compounds consisting of tetrasodium pyrophosphate, trisodium monohydrogenpyrophosphate, disodium dihydrogenpyrophosphate and monosodium trihydrogenpyrophosphate. In use of this heat accumulating material, the sodium acetate trihydrate would not be overcooled owing to the overcooling preventing function of the nucleation catalyst but is unfailingly crystallized at a temperature close to the fusion point thereof to radiate latent heat of fusion. The overcooling preventing performance of the nucleation catalyst is not deteriorated even if it is subjected to more than 1,000 cycles of repetition of fusion and solidification, and thus the heat accumulating material maintains a very stabilized heat absorbing and radiating capacity.

Abstract: A supercooling inhibitor comprising a supercooling inhibitor base having all or part of its surface coated with sodium acetate trihydrate. The supercooling inhibitor base comprises one or more members selected from the group consisting of sodium pyrophosphate (Na.sub.4 P.sub.2 O.sub.7), trisodium monohydrogen pyrophosphate (Na.sub.3 HP.sub.2 O.sub.7), disodium dihydrogen pyrophosphate (Na.sub.2 H.sub.2 P.sub.2 O.sub.7), monosodium trihydrogen pyrophosphate (NaH.sub.3 P.sub.2 O.sub.7), sodium pyrophosphate decahydrate (Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O), and disodium dihydrogen pyrophosphate hexahydrate (Na.sub.2 H.sub.2 P.sub.2 O.sub.7.6H.sub.2 O). The supercooling inhibitor of the present invention is useful for inhibiting the supercooling of sodium acetate trihydrate which is used as a heat regenerating material utilizing heat of fusion.