A new distillation apparatus is described in which the acetaldehyde formed by action of KMnO4 on the lactic acid is carried over into the receiver in a water-free condition by a continuous current of air. The end of the distilling tube is removable and is used as a stirrer during subsequent titration. The receiver is deep, so that there is a very thick layer of liquid and a very faint trace of color is readily discernible. The KMnO4 drops into the reaction vessel without coming into contact with the acetaldehyde produced.