Illium-349
From superman.nu: Supermanica
A rare radioactive element "whose rays can change the size of the body!" By October 1958 the renegade Kandorian scientist Zak-Kul has successfully "isolated" the rare element and used it to create an ingenius reducing and enlarging ray which can be used to either shrink or enlarge a person to any chosen size (Act No.245: "The Shrinking Superman!"). In October 1964, while experimenting with the substance in the hope of using it to power an "enlarger ray" with which to safely enlarge Kandor and its population to normal human size, the elderly Kandorian scientist Nor-Kan is struck in the brain by "a fatal dose of radiation" and dies almost instantly (Act No.317: "Superman's Rainbow Face!"). --TGSB
[see also Illium]
