## Chemistry: The Molecular Science (5th Edition)

Less than 120 degrees C and less than $10^{-4} atm$
Sublimation occurs when going straight from vapor to solid state. Thus, we look for where the vapor region is directly bordering the solid regions. When we do this, we see that the temperature must be less than 120 degrees C, and the pressure must be less than $10^{-4}$ atm for sublimation to be possible.