Dissolvedgas

Dissolved gas refers to gas molecules present in a liquid as a solution rather than as dispersed bubbles. In equilibrium, the amount of gas dissolved in a liquid is determined by the partial pressure of the gas above the liquid and by temperature, in accordance with Henry's law: C = k_H p_gas, where C is the dissolved-gas concentration and k_H is Henry's constant for the specific gas–solvent pair. The solubility increases with higher partial pressure and decreases with rising temperature. Other factors such as salinity and the presence of solutes can modify solubility.

Concentrations are commonly expressed in molarity, molality, mole fraction, or as partial pressure data. In water, dissolved oxygen is essential for aquatic life, while dissolved carbon dioxide is important for buffering and carbonate chemistry. In the beverage industry, dissolving CO2 under pressure produces carbonated drinks; rapid depressurization or heating causes degassing and bubbling. In natural waters, supersaturation with nitrogen or oxygen can occur from rapid decompression or gas production, potentially harming organisms.

Measurement methods include chemical titration for oxygen (Winkler method) and modern optical or electrochemical sensors for dissolved oxygen or carbon dioxide; gas chromatography can analyze dissolved gases in more complex matrices. Applications span environmental monitoring, aquaculture, water treatment, brewing, and oil and gas industries where dissolved-gas content affects corrosion, safety, and product quality.