The temperature variation of the fractionation of oxygen in exchange reactions between dissolved carbonate and water and between calcite and water and calculated on theoretical grounds, and checked experimentally. In the course of the experiments it was necessary to investigate several methods of decomposing calcium carbonate to carbon dioxide for mass spectrometer analysis. A method was developed for growing calcium carbonate from solution with the same isotopic composition as the carbonate shells of organisms produced at the same temperature from water of the same isotopic composition, and the results of these experiments at various temperatures are expressed in an equation relating the temperature of formation with the isotopic composition of the calcium carbonate and of the water.

On the Isotopic Chemistry of Carbonates and a Paleotemperature Scale

羟氨苄青霉素引起大疱性类天疱疮样疹

Uranium solution-mineral equilibria at low temperatures with applications to sedimentary ore deposits

A table is presented of a complete list of the radioactive and stable isotopes, with a number of their salient features, as recorded in the literature or by private communications up to February 1958. (W.D.M.)

Table of isotopes

Electronegativity values from thermochemical data

The production cross sections for the actinides from $^{136}\mathrm{Xe}$ bombardments of $^{249}\mathrm{Cf}$ at energies 1.02, 1.09, and 1.16 times the Coulomb barrier were determined. Chemical fractions of the individual actinide elements were prepared and the gamma, alpha, and spontaneous fission activities of the actinide isotopes were measured. The cross section distributions are presented and compared with those from other heavy ion bombardments of actinide targets. Conclusions are drawn as to the utility of these heavy ion bombardments for producing unknown isotopes in the actinide region. It is shown that for new neutron-rich actinide isotopes with atomic numbers smaller than that of the target these very heavy ion bombardments are perhaps the best method of production, and when using the most neutron-rich targets available new neutron-rich isotopes should be produced in quantities sufficient for their identification and study.

Actinide production in Xe 136 bombardments of Cf 249

: Some evidence as to the chemical nature of the new element californium is presented. The chemical separation and identification of the new element was accomplished through the use of ion-exchange adsorption methods employing the resin Dowex-50. Californium appears in the eka-dysprosium position on elution curves containing berkelium and curium as reference points--that is, it precedes berkelium and curium off the column as dysprosium precedes terbium and gadolinium. The experiments so far have revealed only the tripositive oxidation state of eka-dysprosium character and suggest either that higher oxidation states are not stable in aqueous solution or that the rates of oxidation are slow.

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Chemical Properties of Californium

Fast Breeder Reactors

The Synthetic Elements

The existence of zinc radioactivities with half-lives 57 minutes and 13.8 hours is confirmed, by deuteron activation of zinc. In addition, it is found that both these activities are produced by deuteron and by fast neutron irradiation of gallium, so that the two periods must be due to isomers of ${\mathrm{Zn}}^{69}$. Both emit negative electrons and the properties of their radiations are given. It is shown that ${\mathrm{Zn}}^{65}$, produced through deuteron bombardment of zinc, has a half-life of 250 days, agreeing with the period found by others after proton and deuteron bombardment of copper. This isotope appears to decay by $K$ electron capture and also, to a lesser extent, by positron emission. No evidence has been found for radioactive ${\mathrm{Zn}}^{71}$. All previously reported zinc activities are discussed and the following table contains all the known periods that are believed to be genuine.

Glenn T. Seaborg

Papers

Actinide production in Xe 136 bombardments of Cf 249

Chemical Properties of Californium

Fast Breeder Reactors

The Synthetic Elements

Radioactive Isotopes of Zinc