The present volume Uranium C5 covers the physical properties of U0 - the production 2 and preparation of U0 were already treated in Uranium C4, whereas the chemical proper 2 ties will be the subject of the forthcoming part C6. U0 is the most important chemical compound in all aspects of nuclear technology. 2 It is and will be for the foreseeable future the fuel for all light and heavy water reactors as well as (in the mixed crystal with Pu0 ) for the fast breeder reactors. Therefore, the 2 nuclear engineer has to understand the behavior of U0 under all conditions existing during 2 operational (and possibly failure) states of a nuclear reactor, e. g. , not only in the solid state but also to some extent in the liquid and gaseous states. Besides high scientific interest in the sometimes unique or unusual properties, e. g. , at low temperatures, a lot of data and physical properties which are critical for its use as a nuclear fuel have been determined more or less accurately. Creep, swelling, irradiation densification, and fission gas behavior in the fuel are properties which have been evaluated up to the high temperatu res (near the melting point) which may exist in U0 fuel due to its low thermal conductivity. 2 Besides these more technical data there have been accumulated a lot of important physical data, e. g.

This volume C 3, as a part of the Gmelin "Thorium" Handbook, Series C, describes the thorium-nitrogen compounds. Included are compounds both of technological importance like the nitrides and the nitrates and those of merely scientific interest, such as amides and related compounds. However, due to the decreasing technical importance of the nuclear thorium fuel cycle, especially with the advanced fuels like the nitride ThN, in recent years, the thorium compounds with nitrogen have been investigated much less extensively than the correspond ing uranium compounds. In order to have the data for the Th-N-X systems accumulated in one specific volume, the decision was made to publish this volume without incorporating other Th systems. ThN is the compound with the lowest N :Th ratio. In addition to its (former) nuclear interest due to its thermal and radiation stability, it has many very interesting physicochemical properties. Thorium nitrate, the other well-investigated compound, is of importance because it is (in the form of an adduct with tri-n-butylphosphate) the extracted compound when burnt-up thorium fuels are reprocessed. Despite the wealth of accumulated data on the chemical and physicochemical properties of the compounds discussed, the knowledge of the compounds and of the systems is far from satisfactory - it must be deepened and improved in further studies. I would like to thank the competent authors for their critical contributions as well as the Gmelin-Institute for the excellent cooperation provided, especially Prof. Dr. Fluck and Dr. Keim, the editor-in-chief of this volume.

The present volume of the Gmelin thorium series describes the solid thorium-carbon compounds with the exception of the carbides and coordination compounds of the type 4 ThAn* X B, where B is a neutral ligand. The complex equilibria of the Th + ion with C-containing complexing agents are treated in the ThD1 volume. A first look into this volume demonstrates that a very large number of ThlV complexes has 4 been prepared. This may be explained by the fact that the Th + ion is the largest tetravalent ion of the periodic table. Therefore, the preparation of complexes with, e. g. , multidentate ligands can give a well-established picture of the coordination number as a function of charge and ionic radius. However, there are very few modern and updated comprehensive treatments of such data. Many compounds described in this volume are characterized by no other means than analytical composition and IR spectra (whereby IR spectra of organic ThlV salts mostly give information only on the ligand). Besides thorium carbonate and carbonato complexes, which are relevant for the environmental behaviour of this radioactive element and some organic complexes like oxalates, which are used in the field of analytical and separation chemistry nearly all other compounds described here are practically only of scientific interest. On the other hand in order to have scientifically reliable data, a very large part of these compounds needs further investigation and characterization.

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.

The present volume describes the general properties of the thorium atom and ions, the thermodynamics of its compounds and solutions, the behavior of solutions and solid com pounds under the influence of its own radiation as well as an external radiation field, and spectroscopic data in great detail. The different chapters are of special interest to scientists who work in these fields, and also in the corresponding fields of other elements. In some special fields there exists a detailed knowledge of this radioelement whereas in other fields, such as M6Bbauer spectra, lower oxidation states, or radiation stability, there are large gaps. Due to the fact that the significance 23 of thorium as a breeder fuel ( 2"fh to be converted to fissile 233U after thermal neutron capture) has decreased within the last decade, the behavior of thorium is not as yet so thoroughly investigated as the heavier radioactive element uranium. Many of these data, however, are not only of academic interest, e.g., the knowledge of atomic spectra is needed for some analytical methods, especially in the trace concentration region. Due to the noble gaS-like electronic configuration of the tetravalent ion, there are no absorption bands in the visible region so that in general spectra and data are very scarce. This volume is a very detailed and critically reviewed compilation, written by experts from the Federal Republic of Germany, Belgium, and the United States.

Astatine is - besides radon and francium - the only natural radioelement which only has short-Lived isotopes, thereby excluding experiments with . . weighable" amounts of the element. This implies that all available data on physics and chemistry of this element are 12 16 based on experiments on the tracer scale with 10- to 10- g - and this will also not change in future because no longer-Lived isotopes as yet known are to be expected. Due to the fact that the only isotope of At occurring in the natural decay series, 219At, results from the 0. 005% a-branching of 223Fr which itself is produced by the only 1. 38% a-branching of 227 Ac - a member of the 235U series - there is no chance to recover substantial amounts of 219At from natural sources for sCientific research of At. All studies, therefore, are being done with the isotopes 209At to 211At having half-lives in the few hours region and being obtained by irradiation of bismuth with a-particles via (a,xn) reactions or by proton irradiation of heavy elements via spallation reactions. The mostly used isotope is 7. 22 h 211At. The fast separation of the obtained At isotopes is no very difficult procedure and is either being done by wet adsorption-precipitation techniques or making use of its high volatility by destilling in air.

Es ist eines der besonderen Ziele des Gmelin-lnstituts, den neuesten Kenntnisstand uber das gesamte Gebiet der Actinidenelemente zu vermitteln. Der erste Schritt in dieser Richtung war die Be arbeitung der Transurane, die jetzt komplett vorliegt. Die entsprechenden Bande uber die Elemente Protactinium und Uran sind in Bearbeitung und werden voraussichtlich 1977 bzw. 1978!1980 erscheinen. Der vorliegende Erganzungsband* "Thorium'" C 2 uber "Ternare und polynare Oxide'" ist der erste Band der Reihe, die dem Element Thorium gewidmet ist. Entsprechend der Unterteilung der Uran- und Transuranebande ist die Beschreibung des Thoriums in vier Teile gegliedert: Teil A "Das Element'" Teil C ,. Verbindungen'" Teil B "Metall und Legierungen"' Teil D "Chemie in Loesung'" Die vorgezogene Herausgabe dieses Bandes wird durch die Tatsache gefoerdert, dass Th0 und 2 ThOrUOrMischoxide speziell fur Hochtemperaturkernreaktoren als Brutstoffe fur die Erzeugung 233 von U von Bedeutung sind. Daher ist es auch von Interesse, nahere Einzelheiten uber die moeg lichen Wechselwirkungen von Spaltproduktoxiden mit Th02 zu erfahren. Der vorliegende Band gibt dazu die Moeglichkeit, als er die Literatur bis Ende 1975 umfasst. Daneben ist es sicher gut, Kenntnis zu erhalten von Lucken experimenteller Ergebnisse auf diesem Gebiet. Dies mag einen Anstoss zu neuen Arbeiten geben. Um einen vollstandigen UEberblick und eine geschlossene Darstellung uber das im Titel genannte Gebiet zu geben, wurden alle ternaren und polynaren Metalloxid-Systeme des Thoriums aufgenommen, fur die nicht ein neuer Gmelin-Band vorlag, ferner sind einige der im Thorium-Hauptband von 1954 aufgefuhrten Literaturzitate mit eingearbeitet.

Die Beschreibung des Urans und seiner Verbindungen, die das Gmelin-Institut mit dem vor- liegenden ersten Erg?nzungsband "Uran" Erg. -Bd., Teil C 3 "Tern?re und polyn?re Oxide" in Angriff genommen hat, ist in vier Teile gegliedert: Teil A "Das Element" Teil C "Verbindungen" Teil B "Metall und Legierungen" Teil D "Chemie in L?sung" Das in diesem Teilband behandelte Gebiet ist einesteils wissenschaftlich von besonderem Interesse - es sei nur erw?hnt, daB bei kaum einem anderen Element tern?re und polyn?re Oxidphasen derart ausgedehnter Nichtst?chiometrie, sowohl im Hinblick auf das jeweilige Uran: Metall-Verh?ltnis als auch hinsichtlich der Sauerstoffst?chiometrie - bekannt sind wie bei Uran. Andernteils besitzen tern?re Oxide des Urans in der Kerntechnik ei ne liberragende Bedeutung, es sei nur an die Verwendung von (U, Th)02-Mischoxiden in Hochtemperaturreaktoren bzw. von (U, Pu)02-Mischoxiden in Schnellen Brutreaktoren erinnert. Auch entstehen tern?re Oxide des Urans w?hrend des Betriebs von Kernreaktoren durch Festk?rperreaktionen von U0 mit Oxiden 2 von Spaltprodukten, es sei hier nur CS2U04 und seine sch?digende Wirkung auf die Brennelement- hlille erw?hnt. Die Herausgabe des Teilbandes "Tern?re und polyn?re Oxide des Urans" vorab scheint durch die Tatsache angemessen, daB der Kenntnisstand liber dieses Gebiet sich in einem Rahmen be- grenzt, der dieses Gebiet zwar als nicht abgeschlossen - welches Gebiet der Naturwissenschaften kann dies fUr sich in Anspruch nehmen - doch als soweit untersucht erkennen I?Bt, daB sensatio- nelle Neuentdeckungen kaum mehr zu erwarten sind. Ais mich die Direktorin des Gmelin-Instituts, Frau Prof. Dr.