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.

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.

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.

A riveting look at how an alternative source of energy is revoluntionising nuclear power, promising a safe and clean future for millions, and why thorium was sidelined at the height of the Cold War In this groundbreaking account of an energy revolution in the making, award-winning science writer Richard Martin introduces us to thorium, a radioactive element and alternative nuclear fuel that is far safer, cleaner, and more abundant than uranium. At the dawn of the Atomic Age, thorium and uranium seemed to be in close competition as the fuel of the future. Uranium, with its ability to undergo fission and produce explosive material for atomic weapons, won out over its more pacific sister element, relegating thorium to the dustbin of science. Now, as we grapple with the perils of nuclear energy and rogue atomic weapons, and mankind confronts the specter of global climate change, thorium is re-emerging as the overlooked energy source as a small group of activists and outsiders is working, with the help of Silicon Valley investors, to build a thorium-power industry. In the first book mainstream book to tackle these issues, Superfuel is a story of rediscovery of a long lost technology that has the power to transform the world's future, and the story of the pacifists, who were sidelined in favour of atomic weapon hawks, but who can wean us off our fossil-fuel addiction and avert the risk of nuclear meltdown for ever.

This volume comprises the compounds of thorium with the 4th main group elements silicon and germanium and all 5th main group elements except nitrogen. On the subject of ternary and polynary compounds containing oxygen, only those compounds with phosphorus are included (e.g., phosphates, hypophosphates, or phosphinates). Similar compounds of the other ele ments like silicates, arsenates, etc. were already treated in "Thorium" Suppl. Vol. C 2, 1976. Most of the compounds in the different systems treated in this volume are of scientific interest because of their special physical and chemical properties. On the other hand, there are also many compounds wh ich are of specific technological interest, mainly in the nuclear field. Refractory compounds like ThSi or ThP have potential interest as nuclear fuel for special reactors due to their physical properties like good heat conductivity and their chemical stability, e.g., against the corrosion of cladding alloys for nuclear fuel elements. Due to the present situation in the further development of the thorium nuclear fuel cycle, their large potential has not yet been fully investigated. For most of the binary and ternary phases in these systems, we presently have good knowledge about the preparation of the compounds and their physical and chemical properties. But nevertheless, there are still a lot of open questions concerning phase equilibria, solid solutions, and homogeneity of some of the phases described in this volume.

This book describes hazards from radon progeny and other alpha-emitters that humans may inhale or ingest from their environment. In their analysis, the authors summarize in one document clinical and epidemiological evidence, the results of animal studies, research on alpha-particle damage at the cellular level, metabolic pathways for internal alpha-emitters, dosimetry and microdosimetry of radionuclides deposited in specific tissues, and the chemical toxicity of some low-specific-activity alpha-emitters. Techniques for estimating the risks to humans posed by radon and other internally deposited alpha-emitters are offered, along with a discussion of formulas, models, methods, and the level of uncertainty inherent in the risk estimates.