Process for the manufacture of butynediol

An improved process for the continuous production of butynediol by reaction of acetylene and formaldehyde in aqueous solution in the presence of a catalyst containing copper acetylide, the catalyst being contained in a reaction vessel in the form of a suspension or a fixed bed at a pressure of from atmospheric to about 50 bars and a temperature of from about 60.degree. to about 100.degree.C, the improvement consisting in mixing gaseous acetylene and aqueous formaldehyde outside the reaction vessel or at its inlet and passing the mixture into the reaction vessel in the absence of a coherent gas phase, and withdrawing the reaction mixture from said vessel at a point where any gas phase or bubbles formed are removed from the vessel together with the reaction mixture being withdrawn.