Ultrasonic humidifiers are the quietest humidifiers available, and the ideal choice when noise level is a concern (if you are a light sleeper). In general, a warm moisture humidifier will be much quieter than a cool moisture evaporative humidifier.
Iodine is a chemical element with symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a lustrous, purple-black metallic solid at a standard conditions that sublimes readily to form a violet gas. The elemental form was discovered by the French chemist Bernard Courtois in 1811.
Iodine is a solid. On warming[ or even w/o heating] it will sublime to give violet vapors.In both solid & gas states, it remains as I2 molecule. Why it is a solid is a big Q ! we cannot explain all the whys in Chemistry ! It is a fact seen in lab that : iron is a solid, so also iodine, sugar, wood, ....