Showing papers in "Journal of Research of the National Bureau of Standards Section A: Physics and Chemistry in 1960"

Theory of Formation of Polymer Crystals with Folded Chains in Dilute Solution.

Abstract: A detailed interpretation of the kinetics of homogeneous nucleation and growth of crystals of a linear homopolymer from dilute solution is given. The probability of forming both nuclei with folded chains, and conventional bundlelike nuclei, from dilute solution is analyzed. It is predicted that at sufficiently high dilution, critical nuclei of length lp* will be formed from single polymer molecules by sharp folding of the chain backbone. The step height of the nucleus is given approximately by lp*=4σe/Δf . Here σe is the free energy required to form a unit area of the loop-containing end surfaces, and Δf is the free energy difference per unit volume of crystal between the crystalline and solution states. The quantity Δf is approximately proportional to the degree of supercooling ΔT. The growth of these nuclei is then analyzed. After growth, the resulting crystal is flat and platelike, the loops formed by the chain folds being on the upper and lower surfaces. Kinetic factors determine that the distance between the flat surfaces in the grown crystal will vary over only a narrow range about a value that is in the vicinity of 1*=4σe /Δf. (Neglecting effects due to edge free energies, the theoretical upper and lower limits are 1*=4σe /Δf and 1*=2σe /Δf, respectively.) In some cases the predicted temperature dependence of the step height of the grown crystal, 1* = const./ΔT, may be modified by the existence of a constant term resulting from the presence of an edge free energy ϵp . A grown loop-type crystal is predicted to be stable in comparison with a bundlelike crystal of the same shape and volume in a sufficiently dilute solution. The logarithm of the nucleation rate is approximately proportional to 1/(ΔT)2 near the melting point. The exponent n in the free growth rate law is predicted under various assumptions. To the extent that comparison is possible, the predictions given agree with the experimental results obtained by Keller and O'Connor and others on single crystals of unbranched polyethylene grown from dilute solution. A survey is given of homogeneous nucleation in bulk polymers, where the conventional bundlelike nucleus containing segments from many different molecules is valid, and the essential results compared with those calculated for the dilute solution case. The theory given for loop nuclei is both general and precise enough at the critical points to suggest that, on crystallization from sufficiently dilute solution, crystals of a definite step height are commonly to be expected for other crystallizable linear polymers than polyethylene, provided loop formation is sterically possible.

Elastic Constants of Synthetic Single Crystal Corundum at Room Temperature.

Abstract: The six elastic constants (and six elastic compliances) of corundum were determined in the kilocycle per second frequency range by an accurate resonance method. The results were checked in the megacycle per second range with a less accurate, pulse velocity method. The elastic moduli for polycrystalline alumina calculated from the single crystal compliances determined by the resonance method are in good agreement with experimental values obtained on high density polycrystalline alumina. The variation of Young's modulus and of the shear modulus with orientation was calculated from the compliances and the results are shown graphically. The results of the present work do not agree well with previous work on single crystal sapphire. The specification of orientation and the theory used to calculate the elastic constants are given in detail to support the contention that the results of the present work are correct.

Phase Equilibria in Systems Involving the Rare-Earth Oxides. Part I. Polymorphism of the Oxides of the Trivalent Rare-Earth Ions.

Abstract: The polymorphic relationships of the pure rare-earth oxides were reinvestigated usirg x-ray diffraction methods for identification of phases. The oxides of the trivalent rare earth ions crystallize in three different types: A, B, and C. Each oxide has only one truly stable polymorph: La/sub 2/O/sub 3/, Ce/ sub 2/C/sub 3/, Pr,O/sub 3/, and Nd/sub 2/C/sub 3/ belong to the A type; Sm/sub 2/ )/sub 3/ Eu/sub 2.O/sub 3/, and Gd/sub 2/0/sub 3/ to the B type; Tb/sub 2/,0/sub 3/, Dy/sub 2/O/sub 3/ Ho/sub 2/Cl, Er/sub 2/C/sub 3/, Tm/sub 2/O/sub 3/, Yb/sub 2/ O/sub 3/, and Lu/sub 2/O/sub 3/ to the C type. In addition Nd/sub 2/O/sub 3/, Sm/ sub 2/, C/sub 2/, Eu/sub 2/O/sub 0/, and Gd/su b 2/O/sub 3/ have lowtemperature, apparently metastable, C-type polymorphs. The low-temperature form inverts irreversibly to the stable form at increasingly higher temperatures for decreasing cation radius. (auth)

The "1958 He4 Scale of Temperatures": Part 1. Introduction.

Abstract: The generally used practical scale of temperatures between 1° and 5.2° K is the He4 vapor pressure scale based on an accepted vapor pressure equation or table. In Sevres (near Paris), October 1958, the International Committee on Weights and Measures recommended for international use the "1958 He4 Scale" based on a vapor pressure table arrived at through international cooperation and agreement. This table resulted from a consideration of all reliable He4 vapor pressure data obtained using gas thermometers, and paramagnetic susceptibility and carbon resistor thermometers. The theoretical vapor pressure equation from statistical thermodynamics was used with thermodynamic data on liquid He4 and the vapor equation of state to insure satisfactory agreement of the vapor pressure table with reliable thermodynamic data.

A Comparison of Experimental and Theoretical Relations Between Young's Modulus and the Flexural and Longitudinal Resonance Frequencies of Uniform Bars.

Abstract: The relations from which Young's modulus may be computed from mechanical flexural and longitudinal resonance frequencies have been established by an empirical method using two sets of steel bars. Both sets contained rectangular and cylindrical specimens. For longitudinal vibration of cylindrical specimens, the agreement between the empirical curves and Bancroft's corresponding theoretical relation was within experimental error if Poisson's ratio for both sets is taken to be 0.292. For flexural vibrations, the agreement between the empirical curve and the corresponding theoretical relation developed by Pickett is also within experimental error for about the same value of Poisson's ratio for the rectangular specimens of both sets; but for cylindrical specimens, the empirical values are somewhat lower than those predicted by the theory.

Energy levels and spectrum of neutral helium (4He I)

Abstract: A table of energy levels based on the most accurate observations now available is given for the neutral 4He atom. The wavelengths contained in a revised list of 4He I lines from 320 A to 21132 A are also based on the best measurements, over half of them having been calculated from the wavenumber separations of appropriate levels. Several previously disturbing features of the 4He term scheme are obviated by the revised level values. In a discussion of the experimental results for this spectrum some comparisons with theory are made.

Standard of Spectral Radiance for the Region of 0.25 to 2.6 Microns.

Abstract: This paper contains information relating to the setting up of standard blackbodies for use through the temperature range of about 1,400° to 2,400° K and their use in the calibration of tungsten strip lamps as laboratory standards of spectral radiance for the wavelength region of 0.25 to 2.6 microns. A graphite blackbody is described and representative data are given on the spectral characteristics of the new lamp standard as compared to blackbodies at several selected temperatures.

Some Observations on the Calcium Aluminate Carbonate Hydrates.

Abstract: Two calcium aluminate carbonate hydrates, previously reported in the literature, were prepared and various properties determined. The compound 3CaO·Al2O3·CaCO3·11H2O, was prepared by precipitation from mixtures of solutions of calcium aluminate, calcium hydroxide and sodium carbonate; and, in less pure form, by several other means. It forms thin hexagonal plates having refractive indices 1.532 and 1.554. From X-ray diffraction, cell parameters, calculated on the assumption of hexagonal symmetry, are a=8.716, c=7.565. On continued exposure to atmospheric carbon dioxide it is decomposed to calcium carbonate and hydrated alumina. The compound 3CaO·Al2O3·3CaCO3·32H2O, was prepared by precipitation from mixtures of ammonium bicarbonate, calcium aluminate, and calcium hydroxide in aqueous sucrose solution. It crystallized as spherulites of minute needles. Other methods produced individual crystals, some tubular, but only in minute quantities or mixed with other phases. X-ray diffraction indicates isomorphism with 3CaO·Al2O3·3CaSO4·32H2O. 3CaO·Al2O3·3CaCO3·32H2O is, in general, less stable than the monocarbonate complex. The needle-form "silicoaluminate" reported by Flint and Wells was re-examined. It was concluded that the phase probably contains CO2 as well as SiO2, but the exact composition is in doubt.

Vibration-Rotation Structure in Absorption Bands for the Calibration of Spectrometers From 2 to 16 Microns.

Abstract: Reports discussing bands of common gases that have been tabulated and remeasured wherever necessary from 2 to 16 microns to obtain an accuracy of about 0.03 cm-1 throughout the region and to provide good calibrating points at frequent intervals. Some 600 rotation-vibration lines are illustrated in 20 spectrograms and wavenumbers are listed in companion tables with considerable intercomparison with worthy data obtained in other laboratories. The absorption bands were remeasured or calibrated by using either a precisely graduated grating circle or standard atomic lines with the fringe system formed by a Fabry-Perot interferometer. Characteristic features of the individual bands are discussed briefly and references to other publications are given. The substances used for calibration include H2O, CO2, CO, HCl, HBr, NH3, C2H2, CH4, N2O, and polystyrene film.

Phase equilibria in systems involving the rare-earth oxides. Part II. Solid state reactions in trivalent rare-earth oxide systems

Abstract: Selected mixtures in 21 binary and 9 ternary rare-earth oxide systems were studied by x-ray diffraction after heat treatment at 1650 deg C and above. Two graphs were drawn to show specific regions of stability for the various structure types. Each gives the average ionic radius of constituent cations versus the mole percent of the smaller cation. One diagram is essentially divided into areas of solid solution of the A, B, and C rare-earth oxide structure types. The other indicates a field of perovskite-type compcunds bordered by regions of A, B, or C solid solutions. These diagrams were used to predict the subsolidus phase diagrams of a number of systems. A total of forty- one subsolidus binary and one ternary rare-earth oxide systems were given. A tolerance factor equal to 0.77 was assigned as the minimum value for the formation of a perovskitetype compound. (auth)

The Spectrum of Singly Ionized Atomic Iodine (I ii).

Abstract: The I ii spectrum has been excited in electrodeless lamps and photographed from 655 A to 11084 A. Wavelengths and estimated intensities are given for almost 2,400 lines. A revision and extension of the earlier analyses of this spectrum has increased the number of known even levels from 43 to 124, and the number of odd levels from 55 to 190. New gJ -factors are given for 46 levels, and the previous designations of 40 levels are changed. Improved measurements in the vacuum ultraviolet region give a correction of 7.4 cm-1 to be subtracted from the values listed in Atomic Energy Levels, Vol. 3 (1958), for all levels above the ground configuration. The approximately 1,800 classified lines now include all of the strongest lines. The 1S0 of the ground configuration 5s 25p 4 has been found, and this configuration has been fitted to intermediate coupling theory. Magnetic dipole transitions between levels of the ground configuration, 3P2-1D2 (7282 A) and 3P1-1S0 (4460 A), have been observed and their nature confirmed by the Zeeman effect. The line 5p 4 3P2-1D2 shows hyperfine structure which is in approximate agreement with a theoretical calculation of the expected structure. New levels have been found for almost all higher configurations. All previously known series have been extended and new ones found. From one of the new series, 5 p 3 ( 4 S ° ) 5 - 12 g 5 G 6 ° , the principal ionization energy for I ii (154304 ±1 cm-1) has been derived. The results of the analysis are compared with theoretical expectations in a number of cases.

Infrared Absorption Spectrum of Methane From 2470 to 3200 cm-1.

Abstract: The absorption spectrum of methane has been measured from 2470 to 3200 cm-1 with a high-resolution infrared spectrometer. Pressures from 0.01 to 4.5 cm of the gas were used in order to observe both intense and weak lines. A total of 2,460 lines were measured in the entire region. The v 3 band at 3018 cm-1 was measured at very slow scanning rates and the lines of the P and R branches were resolved into several components. The observed spectrum is shown in five figures.

Determination of the Value of the Faraday With a Silver-Perchloric Acid Coulometer.

Abstract: An accurate value of the faraday has been determined by the electrolytic dissolution of metallic silver in aqueous solutions of perchloric acid. Standards of electric current, mass, and time as maintained by the National Bureau of Standards were utilized in the determinations. The electric current was measured in terms of the standards of electromotive force and electrical resistance. Silver of high purity, freed from oxygen, was used. The value of the faraday was found to be faraday = 96516.5 ± 2 . 4 coulombs gram-equivalen t - 1 ( physical scale ) , faraday = 96490.0 ± 2 . 4 coulombs gram-equivalen t - 1 ( chemical scale ) . These values were obtained using 107.9028±0.0013 and 107.8731±0.0013, for the atomic weight of silver on the physical and chemical scales, respectively. The electrochemical equivalent of silver was found to be electrochemical equivalent of silver = 1.117972 ± 0.000019 milligram coulom b - 1 . This value may be used in an alternate method of defining the ampere in absolute value, namely, that steady current which will dissolve 1.117972 milligrams of silver per second and depends only on the standards of mass and time. The indicated uncertainties are overall limits of error based on 95 percent confidence limits for the mean and allowances for the effects of known sources of possible systematic error.

Acid Dissociation Constant and Related Thermodynamic Quantities for Triethanolammonium Ion in Water From 0 to 50°C.

Abstract: Earlier studies of the dissociation constants of monoethanolammonium and diethanolammonium ions and the thermodynamic constants for the dissociation processes have been supplemented by a similar study of triethanolammonium ion from 0° to 50° C. The dissociation constant (Kbh ) is given by the formula - log K b h = 1341.16 / T + 4.6252 - 0.0045666 T where T is in degrees Kelvin. The order of acidic strengths of the ions is as follows: Triethanolammonium >diethanolammonium>monethanolammonium. Conversely, monoethanolamine is the strongest of the three bases. The thermodynamic constants for the dissociation of one mole of triethanolammonium ion in the standard state at 25° C are as follows: Heat content change (ΔH°) 33.450 joule mole-1; entropy change (ΔS°), -36.4 joule deg-1 mole-1; heat-capacity change ( Δ C p ° ) , 52 joule deg-1 mole-1.

Some Effects of Aging on the Surface Area of Portland Cement Paste.

Abstract: A hardened cement paste cured at room temperature, from which part of the evaporable water has been removed by vacuum drying, has been studied. The surface area has been shown to decrease with time depending upon the amount of evaporable water left in the paste. This change is the opposite of that usually observed during hydration and probably represents some collodial growth phenomena analogous to aging observed in other collodial gels. Both water vapor and nitrogen adsorption measurements have been used to show the effects of aging in cement paste. Wet or dry paste is shown to undergo less change than paste of intermediate evaporable water content, so that if surface area after storage is plotted as a function of evaporable water content, a curve with a minimum is obtained. With increasing storage temperature there is some indication that this minimum might shift towards lower water content. Aging is shown to occur during the initial drying of a cement paste, so that even the initial surface area of a cement paste depends upon the manner in which the paste has been dried.

Conformations of the Pyranoid Sugars. II. Infrared Absorption Spectra of Some Aldopyranosides.

Abstract: The conformations of twenty-four aldopyranosides have been studied by analysis of their infrared absorption spectra. The most stable conformations of twelve of the glycosides had previously been assigned by Reeves from a study of their instability factors; these conformations were assumed to apply to the crystalline state, for which the spectra had been recorded. The compounds were classified into (a) configurationally and (b) structurally related groups, and the spectra were intercompared. The analysis revealed groups of absorption bands which showed a concerted shift on change of anomeric disposition. With these groups of absorption bands thus identified, intercomparison with nine of the remaining spectra afforded evidence that the anomeric group (1) is axial in methyl d-glycero-α-l-gluco-heptopyranoside, methyl d-glycero-α-l-manno-heptopyranoside, and methyl d-glycero-α-d-gulo-heptopyranoside; (2) is equatorial in methyl 6-deoxy-β-l-mannopyranoside, methyl d-glycero-β-d-gulo-heptopyranoside, and cyclohexyl d-glycero-β-d-gulo-heptopyrnoside; and (3) either is quasi or occurs as different (or mixed) axial and equatorial forms in methyl α-d-lyxopranoside, methyl β-d-lyxopranoside, and (possibly) α-d-methylgulopyranoside. Three of the glycosides were available as their crystalline complexes with calcium chloride. The spectra of these complexes were also examined, and the effect of co-crystallization with calcium chloride is pointed out.

Photovoltaic Effect Produced in Silicon Solar Cells by X- and Gamma Rays.

Abstract: The open-circuit voltage and photocurrent produced in a silicon solar cell by x and gamma rays were measured as a function of exposure dose rate, cell temperature, angle of incidence of radiation, and photon energy. This photoresponse was stable and proportional to the exposure dose rate, which was applied up to a maximum of 1.8 x 10/sup 6/ r/hr for x rays and 4 x 10/sup 2/ r/hr for Co/sup 60/ gamma rays. At an exposure dose rate of 1 roentgen per minute the response was of the order of 10/sup -5/ volt for the open-circuit voltage and 10/ sup -8/ ampere for the photocurrent. At high exposure dose rates of Co/sup 60/ gamma rays, radiation damage became apparent. The temperature dependence of the photoresponse was controlled by the temperature dependence of the cell resistance. The directional dependence of the photoresponse varied with the quality of radiation and for Co/sup 60/ gamma rays wse very small for angles from 0 to 70 deg . The photoresponse decreseed with increasing photon energy but changed only little between 200 and 1,250 kilo electron volts. The ratio of the response to x rays of 38 kilo electron volts effective energy and that tomore » Co/sup 60/ gamma rays was approximately 6: 1. An approximate value of the thickness of the effective p- n junction layer is deduced from the energy dependence. (auth)« less

Nitriding Phenomena in Titanium and the 6Al-4V Titanium Alloy.

Abstract: Nitriding unalloyed titanium in purified nitrogen at 1,800° F produced a uniformly thick case that consisted of five distinct zones. The same treatment applied to a 6Al-4V titanium alloy resulted in a thinner nitride case that consisted of three zones and elongated nitride grains that penetrated into the core at approximately 45 degrees to the specimen surface. The aluminum appears to be responsible for the formation of the elongated grains. These grains, in turn, appear to be responsible for the nitriding having a more adverse effect on the toughness of the alloy than of the unalloyed titanium, as indicated by preliminary impact test results. The nitride case on the titanium appears to increase in thickness with increase in nitriding time without limit. The nitride case exhibits a hardness equivalent to about 77 Rockwell C at the surface down to almost 50 Rockwell C at the interface.

Conformations of the Pyranoid Sugars. I. Classification of Conformers.

Abstract: An improved system is presented for indicating the principal conformations of pyranoid sugars and derivatives, by attaching two symbols to the systematic name. The first symbol shows the kind of pyranoid ring; for example, B = a boat, C = the chair, and S = a skew form. (The three boat and six skew rings are distinguished by subscript numerals referring to exoplanar ring-atoms.) The second symbol differentiates between two conformations that have the same type of ring, by describing as A or E the axial or equatorial character of the reference group at a selected ring-atom. If the anomeric group is not quasi, the α anomeric group is used as the reference group. For sugars and derivatives having a quasi anomeric group, and for relatives lacking an anomeric group, the A or E classification is based on the reference group at the lowest numbered, nonquasi, asymmetric ring-atom.

Tritium-Labeled Compounds III. Aldoses-1-t.

Abstract: In a new method for preparing aldoses labeled with tritium at carbon 1, the aldonic lactone is reduced with lithium borohydride-t in pyridine solution. The method is suitable for preparing aldoses-1-t having high specific activities. The crude product contains a substantial proportion of the corresponding alditol-1-t, but the pure aldose-1-t is readily separated by fractional recrystallization or paper chromotography. By means of an isotope-dilution technique, yields were determined for the following aldoses-1-t and the corresponding alditols-1-t: d-arabinose-1-t, d-xylose-1-t, d-ribose-1-t, d-glucose-1-t, d-galactose-1-t, d-mannose-1-t, l-rhamnose-1-t, maltose-1-t, and lactose-1-t. These labeled materials were also prepared by reducing the corresponding lactones with sodium amalgam in tritiated water. Although this latter method is not suitable for preparing labeled aldoses of high specific activity, the products are more readily purified than those obtained by reducing the lactones with lithium borohydride-t. d-Glucose-1-t, obtained by each of these reduction methods, was oxidized with bromine, and the resulting d-gluconic acid was found to be nonradioactive. Hence, in the samples oxidized, tritium was present only at C1. An apparatus used tor reclaiming tritiated water by freeze-drying is depicted; it incorporates an efficient device for trapping entrained solids or liquids.

Combustion Calorimetry with Fluorine: Constant Pressure Flame Calorimetry.

Abstract: Instruments and methods have been developed and are described for the measurement of heats of reaction between fluorine and other gaseous materials. Verification of the amount of reaction of hydrogenous materials is possible. The estimated accuracy of measurements is about 0.3 percent. Lack of certainty of the magnitude of corrections to be applied for hydrogen fluoride nonideality is an important factor. The heat of formation of hydrogen fluoride is found to be -64.4 ± 0.25 kcal/mole on the basis of the reaction of fluorine with ammonia.

Studies of Beryllium Chromite and Other Beryllia Compounds With R2O3 Oxides.

Abstract: Reactions between BeO and R2O3 oxides at high temperatures were studied. Compound formation was observed between BeO and the following oxides: B2O3, Al2O3, Ga2O3, Y2O3, La2O3, and Cr2O3. No reaction was observed with Sc2O3, ln2O3, and Fe2O3. Detailed studies were made of BeO·Cr2O3 which is isostructural with BeO·Al2O3. BeO·Cr2O3 is a semiconductor. Optical and X-ray data are given for all reaction products.

Dissociation Constant of 4-Aminopyridinium Ion in Water From 0 to 50 °C and Related Thermodynamic Quantities.

Abstract: The dissociation constant of 4-aminopyridinium ion in water at 11 temperatures from 0° to 50° C has been determined from electromotive force measurements of 19 approximately equimolal aqueous buffer solutions of 4-aminopyridine and 4-aminopyridinium chloride. Cells without liquid junction were used; the cell is represented as follows: Pt ; H 2 ( g ) , H 2 NC 5 H 4 N ⋅ HCl ( m 1 ) , H 2 NC 5 H 4 N ( m 2 ) , AgCl ; Ag where m is molality. Between 0° and 50° C, the dissociation constant (Kbh ) is given as a function of temperature (T) in degrees Kelvin by - log K b h = 2575.8 T + 0.08277 + 0.0013093 T The changes of Gibbs free energy (ΔG°), of enthalpy (ΔH°), of entropy (ΔS°), and of heat capacity (ΔCp °) for the dissociation process in the standard state were calculated from the constants of this equation. At 25° C the following values were found: - log K b h = 9.114 , Δ G ° = 52 , 013 j mole - 1 , Δ H ° = 47 , 090 j mole - 1 , Δ S ° = - 16.5 j deg - 1 mole - 1 , Δ C p ° = - 15 j deg - 1 mole - 1 . Thermodynamic constants for the basic dissociation of 4-aminopyridine at 25° C were also computed.

Uranium-Platinum System.

Abstract: The phase diagram of the uranium-platinum system was constructed from data obtained by thermal analysis, metallographic examination, and X-ray diffraction. The system is characterized by four intermetallic compounds: UPt, formed peritectoidally at 961° C; UPt2, formed peritectically at 1,370° C; UPt3, melting congruently at 1,700° C; and UPt5, formed peritectically at 1,460° C. One eutectic occurs at 1,005° C and 12 a/o platinum, and a second at 1,345° C and 87.5 a/o platinum. The maximum solubilities are 4.5 a/o uranium in platinum and 5 a/o platinum in gamma-uranium. Platinum lowers the gamma-beta uranium transformation to 705° C and the beta-alpha transformation to 589° C.

Gamma Irradiation of Hexafluorobenzene.

Abstract: Mixtures of hexafluorobenzene and benzene were irradiated in liquid phase by means of a Co/sup 60/ gamma source at 20 and 218 deg C. Perfluoroheptane and various binary mixtures involving perfluoroheptane, hexafluorobenzene, benzene, and cyclohexane were also irradiated at 20 deg C. Hexafiuorobenzene resembled benzene very closely in its behavior upon radiolysis. Generally the fluorocarbonhydrocarbon mixtures evolved much more SiF/sub 4/ (indicating the formation of HF, which reacts with the glass vessel) than the pure fluorocarbon components. The polymer from hexafluorobenzene-benzene mixtures was probably rich in cyclohexadiene and cyclohexene units, resembling that from pure benzene, and its compcsition ratio exhibited a strong "alternating" tendency. The results are discussed in terms of free-radical and excitedstate mechanisms. At 218 deg C hexafluorobenzene and its mixtures with benzene showed qualitative differences from their behavior at 20 deg C, although the G values for SiF/sub 4/ and polymer remained moderate. (auth)

Note on Particle Velocity in Collisions Between Liquid Drops and Solids.

Abstract: Equations are developed for plane-wave particle velocity produced in solid-against-liquid collisions. An explicit expression for the dimensionless coefficient α that appears in these equations is deduced.

Tritium-Labeled Compounds IV. d-Glucose-6-t, d-Xylose-5-t, and d-Mannitol-1-t.

Abstract: BS>Methods are presented for the preparation of D-glucose6-t. D-xylose- 5-t. and D-mannitol-1-t by the reduction of suitable compounds with lithium borohydride-t in anhydrous tetrahydrofuran. followed by hydrolysis of the products. The starting materials for the reductions are. respectively, 1,2-O- isopropylidene-D-glucurono-6.3-lactone. 5-aldo1.2-O-isopropylidene-D-xylo- pentofuranose. and 2.3: 5.6di-C-isopropylidene-D-mannofuranose. The apparatus and procedure for carrying out the reductions in a closed systems are described. (auth)

Preparation of Sulfur of High Purity.

Abstract: A method is described for producing sulfur that contains less than 1.3×10-5 mole fraction of liquid-soluble, solid-insoluble impurities as determined by the freezing point depression. This corresponds to a purity of 99.999 mole percent. Many of the impurities, including organic matter, are removed by oxidation with sulfuric and nitric acids. The nonvolatile impurities are removed on distilling the sulfur. The residual sulfuric acid is removed by a special extraction with distilled water. Methods are described for determining small amounts of the following impurities: Selenium, tellurium, arsenic, iron, carbon, sulfuric acid, and residue after ignition.

The Third Spectrum of Gold (Au III).

Abstract: The spark spectrum of gold has been photographed in a helium atmosphere from 500 A to 6600 A. About 500 lines have been assigned to the third spectrum, Au III, and separated from those belonging to different stages of ionization, by observation of the polarity of the lines. Sixty two levels have been found: 17 even levels, arising from the 5d9 and 5d8 6s configurations; and 45 odd levels, belonging to the 5d86p and 5d7 6s 6p configurations. All of the expected levels from the configurations 5d9, 5d8 6s and 5d8 6p have been identified except for the very high terms based on the 5d8(1S) core of Au IV. With these levels it was possible to classify 256 lines.