Abstract: The process for the production of butynediol by reacting acetylene and formaldehyde in the presence of a particulate copper acetylide catalyst at temperatures from 60.degree. to 120.degree. C is buffered to a pH of 5.0 to 8.0 by a mixture of sodium carbonate and sodium bicarbonate. The buffer mixture is obtained by scrubbing the recycle gas stream from the reaction with an aqueous solution of sodium carbonate and optionally sodium bicarbonate in a countercurrent absorption tower. The liquid effluent from the tower is split, with a portion going to the reaction as the buffer and the balance being regenerated with sodium hydroxide and recycled to the tower.