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Single crystals of oxalic acid dihydrate are difficult to grow from pure water solution, but good single crystals of the material may be obtained by growth from mixtures of acetone and water. The solvent markedly affects the crystal habit. Crystals grown in mixtures of acetone and water develop the prismatic habit, while those grown in water alone develop the tabular or equant habit. The forms {001}, {110}, and {101} predominate in all cases. Single crystals of anhydrous oxalic acid may also be grown from solution in glacial acetic acid, although specimens more than 2 centimeters in length are difficult to produce. down their lengths, the density and calcium carbonate content determined on 55 Abstract. Three South Atlantic deep sea cores have been dated by the carbon-14 technique, and rates of accumulation of clay and calcium carbonate have been determined. The highest eupelagic clay rates for the Atlantic found to date are in the Argentine Basin, and the lowest are on the Mid-Atlantic Ridge. Abstract. Three South Atlantic deep sea cores have been dated by the carbon-14 technique, and rates of accumulation of clay and calcium carbonate have been determined. The highest eupelagic clay rates for the Atlantic found to date are in the Argentine Basin, and the lowest are on the Mid-Atlantic Ridge.

SynopsisThe diffusion, sedimentation, and viscosity behavior of native DNA has been studied as a function of molecular weight absolutely determined by diffusion and sedimentation measurements between 106 and 20 X lo6 Daltons. Only data for monodisperse subfractions of the polydisperse DNA samples investigated have been compared. They were derived by means of calculations based on individual sedimentation constant distribution and polymer parameters. The inconstancy of these parameters for the semirigid DNA molecules over the range of different subfractions of the polydisperse samples has been taken into account. A detailed description of the corresponding mathematical background as well as of the diffusion measurements has been given in the two preceding papers. For the homologous series of monodisperse native DNA molecules, three-parameter equations have been determined representing the so-[q], so-M, and [q]-M relations as well as the DO-@ and DO-M interdependence over the entire molecular weight range of interest. Furthermore a simple equation is given describing the molecular weight dependence of the Maridelkern-Flory-Scheraga parameter B in terms of so and [?I. The asymptotic value 8" has been determined, primarily by measurements a t finite molecular weights, to be 2.39 X 106, resulting in values near 2.50 X 106 a t M = 108 Daltons. The hydrodynamic properties of our two calf thymus DNA samples of highest molecular weight proved to be influenced by residual protein interactions resulting in a more compact conformation. Further data are given demonstrating the influence of the individual polydispersity of the investigated samples on diffusion constant and molecular weight averages.

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