Dr. Miller said softly, "Of course! Rick, that's brilliant. It fits perfectly!"
Jan Miller wailed, "What does?"
"Dry ice," Rick said.
CHAPTER IX
The Splitting Atoms
The storm had given way to a fine drizzle of rain by morning. Rick stared out the window at the drenched land and considered the angles he had been turning over in his mind.
The dry-ice theory wasn't conclusive, he knew, but it was a strong indication. It didn't explain the Blue Ghost himself, but it could explain the mist.
Dry ice is simply solid carbon dioxide, which is a gas at normal temperatures. It becomes a solid at low temperatures, and because it is harmless, inexpensive, and clean, it is widely used to keep things cold, as in the case of ice-cream route men who have no means of refrigeration.
When the temperature is raised, dry ice passes directly from the solid to the gaseous state. When dropped into water it seems to boil, as the comparative warmth of the water turns it to gas, and it creates a fine white mist.