DURING May 24-26, a conference was held in Paris under the auspices of the five chemical societies which share the amenities of the Maison de la Chimie there. The selected subject was the various aspects of hydrogenation. This is the second occasion on which the same five societies have co-operated. An average attendance of more than three hundred was attracted. The meetings commenced at 4.30 in the afternoon, so enabling the participants to go about their ordinary affairs during the working day. The chief figure at the meeting was Prof. Sabatier of Toulouse, still hale and hearty at eighty-four years of age: his original researches are recognized as having given the first impetus to the study of all subsequent hydrogenation reactions, some of which are technically in the forefront of world interest to-day. The presidents of four of the societies presided in turn over the sittings.