National Geographic : 1951 Dec
© National Geographic Society + Strange Things Happen to Helium Chilled to 456° F. below Zero Within four degrees of absolute zero, where molecular movement stops, helium II in the upright inner glass tube above acts as a solid, liquid, and gas all at once. Such experiments aid the study of atom behavior. Vapor comes from liquid nitrogen, a refrigerant. Ektachromes by Willard R. Culver + "Detective" Dye Reveals Impurities in Oils, Drugs, Cleaning Fluids Chemical sleuths are being developed to detect harm ful or beneficial acids and bases in various materials. Here a yellow liquid turns a colorless fluid magenta if it contains impurities. Molecular models (left) show complex structures of the dyes.