Gases dissolved in solvents are usually low in amount but introduce many impurities to certain systems, thus creating disadvantages or advantages which have so far been seldom reported. Evidence of the effects of dissolved gases as impurities on crystallization is provided here. Four types of gases were used. By bubbling these gases into a solvent, gas-saturated solutions were prepared, whereas the degassed solvent was used as a comparison. The results show that different types of gases (including the degassed solvent) do change the thermodynamic and kinetic aspects to a different degree. The pH values of the epsomite solutions that were saturated with different types of gases turned out to be different compared to the untreated solutions, indicating that the gas-liquid-solid equilibrium varied.