 Dry ice is colorless, non-flammable, with a sour zesty odor, and can lower the pH of a solution when dissolved in water, forming carbonic acid (H2CO3).At pressures below 5.13 atm and temperatures below (the triple point), CO2 changes from a solid to a gas with no intervening liquid form, through a process called sublimation.The opposite process is called deposition, where CO2 changes from the gas to solid phase (dry ice).