Henry’s Law and Raoult’s Law

Abstract

On the 23rd of December 1802, Henry’s paper⁽¹⁵⁶⁾ entitled “Experiments on the quantity of gases absorbed by water, at different temperatures, and under different pressures,” was communicated to the Royal Society. Henry determined the number of cubic inches of gas (H₂, O₂, N₂, H₂S, CO, CO₂, PH₃, N₂O, and carbureted hydrogen gas) absorbed by 100 in.³ of water at 60°F and a pressure p _gas of 1 atm. Later in the 19th century, the volume of gas absorbed by one volume of solvent S at a given temperature t°C and p _gas was called the absorption coefficient, and Henry’s values become for water 0.0161 (H₂), 0.037 (O₂), 0.0153 (N₂), 0.020 (CO), 0.0214 (PH₃), 0.0140 (carbureted hydrogen gas), 0.47 (N₂O), 0.80 (H₂S), and 0.94 (CO₂). Since chemical equations are expressed as mole ratios, I deem it desirable to convert these volume ratios into mole ratios, x _A = number of moles of gas absorbed by one mole of solvent S at t°C and 1 atm. The corresponding form of mole ratio is M _s = number of moles of the liquid S required to absorb one mole of the gas at t°C and 1 atm.