Either of two aliphatic alcohols with the formula C₄H₉OH. Butan-1-ol, CH₃(CH₂)₃OH, is a primary alcohol; r.d. 0.81; m.p. –89.5°C; b.p. 117.3°C. Butan-2-ol, CH₃CH(OH)C₂H₅, is a secondary alcohol; r.d. 0.81; m.p. –114.7°C; b.p. 100°C. Both are colourless volatile liquids obtained from butane and are used as solvents.