Recent laboratory results on the hydration of CO3- and HCO3- are extrapolated to atmospheric conditions to determine the extent of hydration of these ions in the stratosphere and lower ionosphere. Comparison with rocket-borne measurements in the lower ionosphere is made. It is concluded that in the normal nighttime lower ionosphere, monohydrates or dihydrates of the atmospheric negative ions CO3-, HCO3-, and NO3- should be prevalent; however, the extent of hydration is sensitive to atmospheric temperature.