The present volume, Thorium C5, deals with the compounds of thorium and sulfur, selenium, tellurium, and boron, as well as with oxoacid compounds of the three chalcogen elements. Thorium borates have already been treated in Thorium C2. In contrast to the corresponding compounds of uranium the thorium sulfides, etc. , do not show any nuclear or other technological application; they are only of academic interest, despite some very interest ing electronic properties, especially of the 1 : 1 compounds. The thorium-sulfur and the thorium boron systems in particular were studied in detail, so that we have a clear picture of them, whereas there are still a lot of open questions in the systems Th-Se and Th-Te - not very different from other metal chalcogenide systems. Thorium sulfates are of some technological importance because they are formed in solution during recovery of thorium from monazite by sulfuric acid leaching. The very detailed and critical treatment of the chemical and physical properties of the compounds discussed also enables us to find gaps still remaining in our knowledge and thus to initiate new research in this field. I want to thank the two authors, Dr. Horst Wedemeyer (Karlsruhe) and Dr. David Brown (Harwell), for their excellent contributions, the "Literaturabteilung" of the Karlsruhe Nuclear Research Center for its help in providing reports and other documents difficult to procure, as well as the staff of the Gmelin-Institute, especially to Dr. K. -C.

Alloys of Uranium with Alkali Metals, Alkaline Earths, and Elements of Main Groups III and IV. The description of uranium and its compounds, for which the Gmelin Institute has started a series of volumes supplementing the main volume of 1936, follows in its arrangement closely the order chosen for the transuranium volumes. Part A treats "The Element," Part B "The Metal and its Alloys," Part C "The Compounds," Part D "The Chemistry in Solution," and finally Part E "The Coordination Compounds." Part E, "The Coordination Compounds" comprises two volumes which already have been finished and are available - completely written in English. Series A comprises 7 volumes which are all available. Series C will comprise 14 volumes of which only volume 6 is missing. Series D consists of 4 volumes dealing with the chemistry in solution, which already have been finished and are available. The present volume describes the alloys and the intermetallic compounds with the metals of main groups I to IV - those systems with semimetals such as boron and germanium are to be found in corresponding volumes in Uranium C series. In the volume B 2 main emphasis is given to the binary systems. The most frequently investigated systems are uranium-beryllium and uranium-aluminium because of their special scientific (U-Be) and technological (U-Al) importance.