A MECHANISM FOR NUCLEATING SUPERCOOLED LIQUIDS

When crystals of sodium ethanoate trihydrate, sodium thiosulphate pentahydrate, or the eutectic mixture of these salts are placed under pressure between two pieces of a variety of materials, heated above the normal melting temperature of the salt, and then cooled, a reduction in the pressure between the pieces results in the nucleation of the crystallization of supercooled solutions of the salt. It is proposed that microscopic seed crystals of the salts survive the high temperature because of an increase in the normal melting temperature resulting from the extremely high pressures that exist in the small areas of actual contact between the pieces of material. The maximum survival temperature for the seed crystals is related to the hardness of the nucleating materials, and the nucleation mechanism is proposed to be more broadly applicable to the nucleation of the crystallization of a wide variety at supercooled liquids. Tables for bond distances, thermal isotropic factors, atomic coordinates, and interatomic distances are presented.