For gas dissolved in liquid at low concentrations: P_gas = K_H * x_gas. K_H = Henry's constant (units: same as pressure). Higher K_H = lower gas solubility (gas escapes more easily). K_H increases with temperature (gases are less soluble at higher T — unlike most solids). Applications: (1) Carbonated beverages — CO2 dissolved under pressure, escapes when opened (P decreases). (2) Deep-sea diving — N2 dissolves under high pressure (narcosis), released as bubbles during rapid ascent (decompression sickness/bends). Solution: use He/O2 mixture (He has very high K_H, low solubility). (3) Oxygen transport — blood absorbs O2 proportional to its partial pressure in lungs. Henry's law is the limiting case of Raoult's law for the solute in very dilute solutions.