What are the characteristics of helium?
“Helium is next to hydrogen in density, being about one-seventh the weight of air. Stated another way, 1,000 cubic feet of hydrogen at 32 degrees [fahrenheit] temperature, at sea level, will lift 75.1 pounds while the same volume of helium will lift 69.6 pounds.” The Story of the Airship by Hugh Allen 6th ed.: Akron — Goodyear Tire & Rubber Company — c1931 Helium, a by-product of natural gas production, has a lifting capacity of 1.02 kg/m3 (0.0640 lb/ft3).
