The Immortals — Ralph Milne Farley

Brilliant and youthful scientist Charles Deane has discovered a new element, Stratium, which is lighter than air. Upon presenting this new discovery to a learned society of chemists, a sample of Stratium has gone missing and Deane's leading critic, Cairns, is murdered. What is the connection between Stratium and a secret society's obsession with Ichor, the so-called fluid of the immortal gods? An Argosy science fiction classic, out of print for decades-until now.