NEARLY three thousand delegates representing thirteen different German societies took part in a national congress of German chemists held at Munich on July 7-11. Prof. P. Duden of Frankfort presided at the general meeting, which was welcomed by Staatsminister Herr Adolph Wagner. Dr. 0. Nicodemus of Frankfort delivered an address on the development of the chemistry of acetylene and its national importance as a source of raw materials. From acetylene many derivatives of the vinyl group can be made, which can be developed by polymerization to a great variety of valuable synthetic products. Amongst these may be mentioned the unsaturated hydrocarbons isoprene and butadiene, from which synthetic rubber is made, and a chlorinated derivative, chloroprene, which polymerizes seven hundred times as fast as isoprene and gives rise to an oil-proof synthetic rubber. By varying the conditions of polymerization, it is possible to plan the synthesis of products possessing specified physical properties, so that the range of application of these products is increasing rapidly.