ог Key words: Abstraction; dextran; dextrin; free radicals; hydroxyl; polyacrylic; polyethylene imine; polyethylene oxide: polymer degradation; polymethacrylic acid; polypropylene oxide; polyvinyl alcohol; starch. Mixing of aqueous polymer solutions containing Ti3+ and H2O2 in a rapid flow mixer produced radicals by abstraction, OH + RH R+ H2O, which were observed by electron spin resonance. Oscillation of segments was sufficient to narrow the lines to 0.5 2.0 g. Polymers and radicals identified with more less certainty were polyacrylic acid, ·CH(CO2H)CHCH(CO2H)'~~, polymethacrylic acid, 'C(CH3)(CO2H)CHC(CH3)(CO2H), polyvinyl alcohol, CHOHCHCHOH, and one indefinite, polyethylene imine, ~CH2NCH2 or ~~CH2NOCH2~, polyethylene oxide, CH2OCHCH2O. Radicals from polypropylene oxide, dextran, dextrin, soluble starch, and the disaccharide maltose were unidentified; the last three were strikingly similar. Products of secondary C-C scission were not observed with certainty. It is presumed that such reactions are slow compared to the time-scale of the experiment, 10 msec. However, some evidence exists for a very rapid ß–OH loss in carbohydrate radicals and a slow C-O scission in polyethylene oxide radicals. A large number of related small molecule radicals were investigated, and hyperfine splittings and g-values are reported. A mass spectrometric study of the BeO-BeF2 system of high temperatures, J. Efimenko, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 1, 75-80 (Jan.-Feb. 1968). Key words: Beryllium difluoride; beryllium oxide; high temperatures; mass spectrometry; reaction enthalpy; sublimation enthalpy. Mass spectrometric studies were made at high temperatures of the vapors over BeF2(s) and BeO(s) individually and of their mixture. The sublimation enthalpy, AH = 55.56 ± 0.43 kcal/mol, where 1 kcal equals 4184 J, was obtained for BeF2 by the use of a log IT versus 1/T plot. A complex molecule appeared in the BeF2-BeO system at high temperatures which, on the basis of its m/e position, corresponded to Be2OF2. For the reaction, BeO(s)+BeF2(g)=Be2OF2(g), a second law treatment of the data gave an enthalpy value, AH=41.56±1.8 kcal/mol. The data, combined with free energy functions, resulted in a mean reaction enthalpy, AH%=42.6 kcal/mol. The heat of formation for Be2OF2(g), AH;=-288.3 kcal/mol, was computed using the reaction enthalpy based on the second law. Laser induced Raman spectra of some tungstates and molybdates, R. K. Khanna, W. S. Brower, B. R. Guscott, and E. R. Lippincott, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 1, 81-84 (Jan.-Feb. 1968). Key words: Molybdates; Raman spectra; tungstates. The Raman spectra of single crystals of CaWO4, CaMoO4, PbWO., and PbMoO, have been recorded using a He-Ne laser (λ = 6328 Å) and an Argon ion laser (λ = 4880 Å) as the exciting radiation sources. The polarization data have enabled us to classify unambiguously the observed fundamentals into the Raman active species of the point group Can to which these crystals belong. The comparison of the spectra of these crystals in the low frequency region has also enabled us to make a rough classification of the bands into the rotational and the translational lattice vibrations. Valence-only correlation in LiH and BeH+, W. A. Sanders and M. Key words: BeH+; correlation energy; dissociation energy; The pseudonatural orbital procedure has been applied to the calculation of the potential energy curve of LiH and the dissociation energy of BeH+. Only the two-electron bonding pair is correlated and estimates of σ and # type correlation are obtained. The results for LiH are in good agreement with the most accurate previously published calculations. Comparison with experimental results for LiH indicates that the calculated dissociation energies are accurate to about 0.15 to 0.2 eV. Thermalization by elastic collisions: positronium in a rare gas moderator, W: C. Sauder, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 1, 91-93 (Jan.-Feb. 1968). Key words: Elastic collisions; positronium; thermalization. The energy decay of particles moving through a moderating medium is discussed for the case in which only elastic collisions occur between these incoming particles and the moderator atoms; the random thermal motion of the moderator atoms is taken into account. It is shown that if the cross section is independent of particle velocity the equation for the energy decay emerges in a rather simple form involving the hyperbolic cotangent. Finally, the theoretical development is applied to estimating the thermalization time of positronium in rare gas moderators, and is shown to agree with the limited experimental results presently available. Density fluctuations in fluids having an internal degree of freedom, R. D. Mountain, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 1, 95-100 (Jan.-Feb. 1968). Key words: Brillouin scattering; density fluctuations in liquids; Rayleigh scattering; spectral distribution of scattered light; structural relaxation; thermal relaxation; volume viscosity. The frequency spectrum of density fluctuations is calculated for a fluid whose molecules possess an internal degree of freedom which is weakly coupled to the translational degree of freedom of the fluid. Irreversible thermodynamics is used to obtain an equation of motion for the internal degree of freedom. This equation plus the linearized hydrodynamic equations are solved for the frequency spectrum of density fluctuations. The results are compared with a similar calculation involving a frequency dependent volume viscosity. The results are identical for structural relaxation but there is a difference for thermal relaxation. The origin of the difference is discussed and the magnitude of the difference is examined for CCL, and for CS2. March-April 1968 Constant pressure flame calorimetry with fluorine. II. The heat of formation of oxygen difluoride, R. C. King and G. T. Armstrong, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 2, 113-131 (Mar.-Apr. 1968). Key words: Bond energy (O-F); flame calorimetry; flow calorimetry; fluorine; heat of formation; heat of reaction; hydrogen fluoride (aqueous); oxygen; oxygen difluoride; reaction calorimetry; water. The heats of the following reactions were measured directly in an electrically calibrated flame calorimeter operated at one atm pressure and 303 °K. OF2(g) + 2H2(g) + 99H2O(1)→ 2[HF · 50H2O](1) 2O2(g) + H2(g) → H2O(1) The reactants and products were analyzed for each of the reactions. From these heats we calculated the corresponding heats of formation, as follows: The heat of formation of boron carbide, E. S. Domalski and G. T. Armstrong, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 2, 133-139 (Mar.-Apr. 1968). Key words: Bomb calorimeter; boron carbide; boron trifluoride; carbon tetrafluoride; heat of combustion; heat of formation; polytetrafluoroethylene. The standard heat of combustion in fluorine of a boron carbide sample having the composition B4.222C was determined from the heats of combustion of polytetrafluoroethylene and of boron carbide-polytetrafluoroethylene mixtures. The energy of the combustion reaction was measured in an isothermal-jacket bomb calorimeter. From the experimental data, we calculate - 17.1 kcal mol-1 for the heat of formation of boron carbide. By combining all probable errors, we estimate our overall experimental uncertainty to be 2.7 kcal mol-1. The value for the heat of formation of boron carbide is for the phase represented by the formula B4.222 C. Solubility of tris(hydroxymethyl)aminomethane in water-methanol solvent mixtures and medium effects in the dissociation of the protonated base, P. Schindler, R. A. Robinson, and R. G. Bates, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 2, 141-148 (Mar.-Apr. 1968). Key words: Dissociation constant; medium effect; methanol-water solvents; solubility; tris(hydroxymethyl)aminomethane. The dissociation constant of the protonated form of tris(hydroxymethyl)aminomethane has been measured at 25 °C in water-methanol solvents containing 30, 50, 70, and 90 wt percent methanol by means of potentiometric titrations. The solubility of tris(hydroxymethyl)aminomethane at 15, 25, and 35 °C in water-methanol solvents containing from 0 to 100 percent methanol has been determined. The results are discussed in terms of free energies of transfer and "medium effects" for hydrochloric acid, tris(hydroxymethyl)aminomethane, and tris(hydroxymethyl)aminomethane hydrochloride. Calibration of the nickel dimethylglyoxime spectral shift at pressures to 20 kilobars for use in spectroscopic pressure measurement, H. W. Davies, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 2, 149-153 (Mar.-Apr. 1968). Key words: Absorption spectra; diamond-anvil cell; high pressure measurement; nickel dimethylglyoxime. A method for incorporating solid nickel dimethylglyoxime in a liquid enclosed by a gasket in the diamond-anvil high pressure cell is described. A calibration curve relating the spectral shift of the nickel dimethylglyoxime visible absorption band to the known freezing pressures of 14 liquids has been obtained. The equation for the calibration line is Av -158.9 P+1.82 p2 where P is expressed in kilobars. The 90 percent confidence band about the calibration curve has been computed, and the curve has been used to determine the room-temperature freezing pressures of acetone and methylcyclohexane. Second virial coefficient of He' in the temperature range from 2 to 20 °K, M. E. Boyd, S. Y. Larsen, and H. Plumb, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 2, 155-156 (Mar.-Apr. 1968). Key words: He1; low temperature; second virial. We present preliminary values for the second virial coefficient of He in the temperature range from 2 to 20 °K. They were derived from recent sound velocity measurements in the gas made by Plumb and Cataland using an ultrasonic interferometer. Diffusion rates in inorganic nuclear materials, A. L. Dragoo, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 2, 157-173 (Mar.-Apr. 1968). Key words: Chemical interdiffusion; grain-boundary diffusion; intrinsic diffusion; lattice diffusion; self-diffusion; tracer diffusion. The tracer diffusion coefficient, the self-diffusion coefficient, the intrinsic diffusion coefficient and the interdiffusion coefficient are briefly described. Grain boundary and lattice (volume) diffusion are contrasted. The frequency factors (D。) and activation energies (Q) are tabulated for diffusion in the borides, carbides, and oxides of Be, Hf, Mo, Nb, Ta, Th, Ti, and Zr and for diffusion of C, N, and O in these metals. The purity of the solvent media, the preparation and properties of the samples, the method, the type of diffusion coefficient measured and the temperature range are also specified. Effect of oxide additions on the polymorphism of tantalum pentoxide (system Ta2O3-TiO2), J. L. Waring and R. S. Roth, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 2, 175186 (Mar.-Apr. 1968). Key words: Phase equilibria; polymorphism; tantalum pentoxide; titanium dioxide. The phase equilibrium relationships of the TiO2-Ta2O3 system were determined in air. An equimolar compound, TiTa2O7, was found to melt congruently at about 1662 °C and have a monoclinic unit cell a = 20.297 Å, b = 3.804 Å, c = 11.831 Å, ß = 120°14', apparently isostructural with TiNb2O7. In addition, two other compounds are postulated to occur at about TiO2:49Ta2Os and TiO2:7Ta2O, and to dissociate at about 1230 and 1190 °C, respectively. TiO2 apparently accepts a maximum of 9 mole percent Ta2Os in solid solution at 1630 °C. Two eutectics occur in the system at 54 mole percent Ta2O, and 1650 °C and 31 mole percent Ta2Os and 1630 °C. The high temperature form of Ta2O, is apparently triclinic at room temperature with a=3.801 Å, b=3.785 Å, c = 35.74 Å, x=90°54.4', B=90°11.5', and y=89°59,9'. A metastable transition occurs at 320 °C to a monoclinic form which inverts to tetragonal at 920 °C with a = 3.81 Å, c = 36.09 Å. Several intermediate morphotropic phases are found with up to 9 mole percent TiO2 in solid solution. Effect of statistical counting errors on wavelength criteria for x-ray spectra, J. S. Thomsen and F. Y. Yap, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 2, 187-205 (Mar.-Apr. 1968). Key words: Lattice constants; peak intensity; physical constants; spectral line profiles; statistical error analysis; x-ray line shapes; x-ray spectra; x-ray wavelength criteria. Various features of the spectral profile of an x-ray line can be measured with an uncertainty which is only a small fraction of the observed line width. With recent improvements in measurement techniques, statistical errors due to the random fluctuations of the intensities in counter recordings may become significant. The present study considers the effect of such errors on several features of the line profile which could be used for definition of its wavelength. These may be broadly classified into three groups, viz, the peak, the centroid, and the median. In the present analysis the statistical errors associated with these features are compared theoretically, with the assumption of negligible error in angular measurement. Certain systematic errors are also briefly examined. The effects of truncation range, asymmetry, and background intensity are considered, as well as possible optimization of the data-taking procedure. In general, σ, the standard deviation of the wavelength, is given by σ/W=F|(I,T)12, where W is the full width at half-maximum intensity, I, the peak intensity, T the total counting time, and F a dimensionless factor of the order of unity. Thus F may be regarded as a factor of merit for comparing the various cases, a low value of F being desirable. When the form of the line profile is known a priori, it is usually best to make use of this knowledge; e.g., a Lorentzian can be thus fitted with F≈ 0.8 for any of the three wavelength features. Using optimized truncation ranges and including the error in locating end points, one obtains approximately this same F for the centroid or median even without prior knowledge of the profile. In the latter case the value of F for the peak usually ranges from about 1.6 to 2.1. However, the peak is less subject to certain systematic errors and is preferable from the viewpoint of simplicity and historical precedent. It is recommended that use of the peak be continued at present; further study of the problem from the viewpoint of atomic energy level interpretation would be desirable. Thermodynamic properties of ammonia as an ideal gas, L. Haar, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 2,207-216 (Mar.-Apr. 1968). Key words: Ammonia; ideal gas; thermodynamic functions. Thermodynamic functions for ammonia as an ideal gas at one atmosphere pressure have been evaluated. The contribution of the highly anharmonic out-of-plane vibrational mode, including its large coupling with rotation and its coupling with the other vibrational modes, is considered in detail. Tables of Cp/R, (H° - Eo)/RT, (E。° - G°)/RT, and S/R have been calculated at closely spaced intervals from 50 to 5000 °K within an overall uncertainty of less than 0.1 percent at 1000 °K. May-June 1968 Jump rates for point defects in special positions held by a trapping center of noncubic symmetry, H. S. Peiser and J. B. Wachtman, Jr., J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 3, 231-237 (May-June 1968). Key words: Crystal symmetry; equivalent sites; jump rates; point defects; relaxation; trapping center. In a previous paper [J. Phys. Chem. Solids 27, 975 (1966)] the authors have discussed symmetry conditions for equivalence of jump rates operative in point-defect motion between crystallographically equivalent general sites neighboring a trapping center. The treatment is here extended to equivalent special sites to show that the total number of inequivalent jump rates can be expressed as (Ni/Na)-qe-1 where N, and Na are the orders of the symmetry groups of the trap and defect respectively and where qe is the number of independently effective pairs of nonself-inverse symmetry operators (paired with their inverses) all in the symmetry group of the trap. The number qe can be obtained by counting any nonself-inverse operator pair, an element of which, when multiplied by an element of the defect symmetry, equals neither its own inverse nor an element of a pair previously counted. For thermally activated relaxation processes expressions apply for maximum and minimum numbers of jump frequencies involved in complete and partial relaxation processes. For complete relaxation the maximum number is the number of prime factors in the ratio of the order of the symmetry group of the trap to that of the defect group. The minimum number is the minimum number of generators that will raise the defect position symmetry to that of the trap. The thermodynamics of the ternary system; water-potassium chloride-calcium chloride at 25 °C, R. A. Robinson and A. K. Covington, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 3, 239-245 (May-June 1968). Key words: Activity coefficient; calcium chloride; isopiestic measurements; mixed salt solutions; osmotic coefficients; potassium chloride; vapor pressure. Isopiestic vapor pressure measurements have been made on the system: water-potassium chloride-calcium chloride at 25 °C. The osmotic coefficients of the mixed salt solutions and the activity coefficients of each salt in the presence of the other have been evaluated. Force field for SiF4, I. W. Levin and S. Abramowitz, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 3, 247-249 (May-June 1968). Key words: Band contour; Coriolis constant; force field; infrared; isotopic shift; low temperature; SiF.. The force field of SiF, has been determined using both Coriolis coupling constants obtained from an investigation of the band contour of at 195 °K and isotopic shifts. The force fields are equally well determined using both methods and are in agree ment. Blemish formation in processed microfilm, C. 1. Pope, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 3, 251259 (May-June 1968). Key words: Archival record film; blemishes due to aging; colloidal silver; microfilm; microfilm storage cartons; permanent record film; peroxides. Oxidizing and reducing agents generated by paper cartons during storage may react with the image silver to form blemishes. The type of fixing bath, concentration of chlorine in the wash water, washing time and composition of the storage cartons can be factors that accelerate or retard the attack of the peroxide on the image silver. Microfilm washed after fixation in distilled water or chlorine-free tap water formed blemishes when exposed to peroxide paper. A trace of silver chloride in the image silver of processed microfilm augmented the formation of the natural type blemishes when exposed to peroxide paper, but high concentrations of residual silver chloride inhibited blemish formation. During storage, some storage cartons evolved formaldehyde, formic acid, and ammonia which created a chemical environment favorable for blemish formation in microfilm in the presence of peroxide. A correlation was found between the incidence of blemishes and the brand of paper storage cartons. A procedure was developed for testing processed microfilm to determine its susceptibility to blemish formation. According to the present theory, peroxide reacts with the silver in the image, forming colloidal silver which imparts a yellowish or reddish color to the blemishes. Absolute isotopic abundance ratios of common, equal-atom and radiogenic lead isotopic standards, E. J. Catanzaro, T. J. Murphy, W. R. Shields, and E. L. Garner, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 3, 261-267 (MayJune 1968). Key words: Absolute ratios; abundance; isotopic standards; lead. Absolute values have been obtained for the isotopic abundance ratios of common, equal-atom, and radiogenic lead isotopic standards using solid-sample mass spectrometry. Samples of known 208Pb/206 Pb ratio, prepared from nearly pure separated 206 Pb and 208Pb solutions, were used to calibrate the mass spectrometers. Rate of nickel in Al-10 percent Si composites containing nickelcoated sapphire whiskers, H. Yakowitz, W. D. Jenkins, and H. Hahn, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 3, 269-272 (May-June 1968). Key words: Al-10 percent Si alloy; electron probe microanalyzer; fiber composites; matrix-whisker bonding; Ni coated sapphire whiskers; optical metallography; sapphire whiskers. The role of nickel in regard to whisker-matrix bonding in a composite of nickel-coated sapphire whiskers inserted into a matrix of aluminum-10 percent silicon alloy by means of liquid phase hot-pressing was investigated. The study was carried out with the aid of optical and electron microscopy, electron probe microanalysis, and microhardness measurements. Results show that most of the nickel is distributed within the matrix alloy. Some of the nickel apparently interacts with the matrix and forms NiAl,. The presence of NiAl, in this form increases the average hardness of the composite but apparently does not contribute significantly to strengthening of the alloy. Occasionally, clusters or clumps of nickel-rich material which also contains aluminum are found at or very near whisker-matrix interfaces. It is concluded that if any bonding of the nickel to the sapphire occurred, it was in these regions. Finally, a heat treatment to improve nickel to sapphire bonding and hence bonding of the entire composite is suggested. July-August 1968 Mass spectrometric study of photoionization. X. Hydrogen chloride and methyl halides, M. Krauss, J. A. Walker, and V. H. Dibeler, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 4, 281-293 (July-Aug. 1968). Key words: Dissociation energies; HCl; ionization; mass spectrometry; methyl halides; vacuum ultraviolet spectroscopy. Photoionization efficiency curves are obtained for hydrogen chloride and several methyl halides, both ordinary and deuterated, from ionization threshold to 600 Å. Discussion is given on electronic structure of ions, autoionizing Rydberg states, and line-shape behavior. Ionization energies, heats of formation of ions, and bond dissociation energies are tabulated without regard to distribution of energy in internal modes, in relative kinetic energy, or other possible modes. The fourth and fifth spectra of vanadium (V 1V and V v), L. Iglesias, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 4, 295-308 (July-Aug. 1968). Key words: Atomic spectra, V IV and V v; classified lines, V IV and V V spectra; spectra V IV and V v; terms, V IV and V v spectra; vanadium, the fourth and fifth spectra of. The V IV spectrum has been extended by using as light sources a condensed spark and a hollow cathode discharge. With the new data, the experimental interpretation of levels of the 3d2, 3d 4d, 3d 5s, 3d 5p, 3d 4f, 3d 5d and 3d 6s configurations has been completed with the exception of three levels of the 3d 4f and 3d 5d configurations. Four levels of the 3d 5g electron configuration have also been found. These levels account for 340 of the 360 lines assigned to V IV in the region 675 Å - 5940 Å. Three members of the 3d ns series give an ionization potential of 376730±40 cm-1=46.70 volts. The 4d 2D term of V v has also been located in the course of this work. With the aid of the new observations between 675 Å and 2200 Å the value of some levels already known has been improved. Variation of absorptance-curve shape with changes in pigment concentration, G. L. Howett, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 4, 309-340 (July-Aug. 1968). Key words: Absorption; adaptation; Beer's law; chromatic adaptation; color vision; concentration; cones; curve shape; high luminance; metameric matches; pigment; photopigment; vision. A complete quantitative analysis is presented of changes in the shape of the spectral absorptance curve of any Beer's-law pigment solution (or other Bouguer's-law material) as concentration of the pigment, or thickness of the solution layer, is varied. The relative absorptance curve, normalized to unit maximum, is taken as defining the shape of the absolute absorptance curve, and the index of shape change is taken to be the difference between the normalized curves. All concentration changes from infinite decrease to infinite increase are covered, with some extreme cases requiring limit methods. Formulas and graphs are given for determining, as a function of concentration change and peak absolute absorptance of the original curve, where along the curve the shape change is greatest, and how large the maximum change is. Implications for color vision theory are discussed and it is shown that the assumption of low peak absorptances (<10%) for the visual photopigments accounts for the constancy of the color-matching functions for moderate luminances, but not, in itself, for the breakdown of matches at high luminances; while the assumption of high peak absorptances (≈ 80%), although it contradicts recent microspectrophotometric measurements, seems to account for both phenomena. Periodic acid, a novel oxidant of polycyclic, aromatic hydrocarbons, A. J. Fatiadi, J. Res. Nat. Bur. Stand. (U.S.)), 72A (Phys. and Chem.), No. 4, 341-350 (July-Aug. 1968). Key words: Aprotic solvents; aromatic hydrocarbons; malonic acid; periodic acid; pyrene radical; quinones; reaction mechanism; sodium metaperiodate. Certain polycyclic, aromatic hydrocarbons can be oxidized with periodic acid in aprotic solvents containing a small proportion of water. A unique, two-fold character of response to periodic acid by these hydrocarbons has been found: (1) production of a coupling reaction through a radical intermediate [conversion of pyrene into 1,1'-bipyrene, and fluorene into 1,2bis(2,2'-biphenylylene)ethylene] or (2) conversion into quinones by a two-equivalent oxidation mechanism that does not involve a radical intermediate [acenaphthene, anthracene, anthrone, benz[a]anthracene, naphthacene, naphthalene, and phenanthrene]. Little or no reaction was observed when oxidation was attempted with sodium metaperiodate instead of periodic acid. Electron-spin resonance revealed no radical intermediate in the oxidation of malonic acid with either periodic acid or sodium periodate. A galvanic cell with a low emf-temperature coefficient, G. N. Roberts and W. J. Hamer, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 4, 351-354 (July-Aug. 1968). Key words: Cell with low temperature coefficient; double salt; galvanic cells; standard cells. This paper presents data on a modified cadmium sulfate saturated standard cell of the Vosburgh type in which a tertiary amalgam containing 11.2 percent bismuth and 8.4 percent cadmium is used as anode and the double salt, CdSO4 · Na2SO4 · 2H2O is added to the usual CdSO, electrolyte in an amount more than At 25 °C the cell has an emf-temperature coefficient of +13.5 μV/°C while the conventional saturated cadmium sulfate cell has a dE/dT of -49.4 μV/°C. Data on the emf-temperature hysteresis of the cell on cooling and on heating are also given in graphical form. Data on the changes in Gibbs energy, enthalpy, entropy, and heat capacity for the cell reaction are given for the temperature range of 5 to 40 °C. Synthesis of cerite, J. Ito, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 4, 355-358 (July-Aug. 1968). Key words: Ca, Mg phosphate; hydrothermal synthesis; inorganic synthesis; mineral chemistry; rare-earth silicate; xray powder analysis. Some compounds isostructural with cerite have been synthesized hydrothermally at temperatures from 500 to 720 °C. The compositional range for cerite, and its phase relation to the silicate apatites are established in terms of ionic radii of rare-earth and divalent ions. The proposed formula for cerite on the basis of isomorphism with whitlockite, Ca,(PO4)2, is discussed. A solid-solution series between CasP6O24 Ca, Mg2P6O24 (whitlockite-Mg-whitlockite) has been established. Tables of collision integrals for the (m,6) potential function for 10 values of m, M. Klein and F. J. Smith, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 4, 359-424 (July-Aug. 1968). Key words: Collision integrals; diffusion; potential; thermal conductivity; thermal diffusion; transport properties; viscosity. Tables of collision integrals are presented for the (m,6) potential function for 87 reduced temperatures for each of 10 values of m. The exponents m used were m = 9, 12, 15, 18, 21, 24, 30, 40, 50, and 75. Comparisons are made with five other calculations for the case m = 12. The accuracy of the calculation appears to be at least several parts in 10,000. Spectrum of relaxation times in GeO2 glass, A. Napolitano and P. B. Macedo, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 4, 425-433 (July-Aug. 1968). Key words: Activation energy; annealing; germania glass; index of refraction; relaxation times; thermal expansion; two relaxation model; viscosity. Index-of-refraction versus time isotherms have been established for germania glass. Using the crossover technique with air-quenched samples and applying the two relaxation time model previously reported for borosilicate glass, it was found that the width of the spectrum of relaxation times for germania glass was temperature dependent. Upon analyzing this in terms of a distribution of activation energies, the results showed that, similarly to B2O3, activation energies smaller than the activation energy present in the Arrhenius region appear at low tempera Key words: Coulometers; Faraday; inclusions in silver coulometers; values of Faraday. A resumé is given of the determinations of the value of the Faraday. Values obtained by silver deposition, iodide oxidation, oxalate oxidation, the omegatron, and silver dissolution are reviewed. All values are converted to the unified 12C international scale of atomic weights using the international atomic weights of 1967. Values of the Faraday are given in terms of both the NBS (legal) and absolute units of electrical measure. In the latter the new value for the acceleration due to gravity is used in computing the absolute value of electric current. On this basis and using the atomic weight of silver determined by Shields, Craig, and Dibeler, and converting to the 12C scale, the value of the Faraday is 96,486.9 ± 1.6 absolute coulombs per gramequivalent which differs by only 1 part per million from the value recommended by the National Academy of Sciences - National Research Council. If the atomic weight of silver recommended in 1967 by the International Atomic Weight Commission is used, the Faraday on the new gravity value is 96,486.5± 1.6 absolute coulombs per gram-equivalent which differs by 5 parts per million from that recommended by the National Academy of Sciences - National Research Council. No change in the value of the Faraday adopted by the NAS-NRC Committee is recommended. September-October 1968 Studies in bomb calorimetry. A new determination of the energy of combustion of benzoic acid in terms of electrical units, K. L. Churney and G. Armstrong, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 5, 453-465 (Sept.-Oct. 1968). Key words: Benzoic acid, heat of combustion; bomb calorimetry, procedures and errors; bomb-calorimeter, electrical calibration; Dickinson calorimeter; heat of combustion. The heat of combustion of NBS Standard Sample 39 of benzoic acid under standard bomb conditions has been determined in terms of electrical units. A value of -26,434.0 J g-1 was obtained. The total uncertainty in our determination is estimated to be ±3.3 J g-1. The uncertainty due to random errors was 1.7 J g' and is based on the appropriate factors for the Student i distribution at the 95 percent confidence limits for eleven determinations of the energy equivalent of the calorimeter and six determinations of the heat of combustion of benzoic acid. The principal systematic error, neglect of surface temperature correction for our calorimeter, has been assigned a value of ±2.6 J g' until more reliable estimates of the correction can be made. Particular emphasis was placed on improving the precision of a calorimetric measurement over those previously obtained in this laboratory by the use of more sensitive auxiliary measuring equipment and more accurate procedures to evaluate the corrected temperature rise. Effect of low pressures on the room temperature transitions of polytetrafluoroethylene, G. M. Martin and R. K. Eby, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 5, 467470 (Sept.-Oct. 1968). Key words: Dilatometry; enthalpy; entropy; helical molecule; low pressure; phase diagram; polytetrafluoroethylene; transitions; triple point. Between approximately 20 and 30 °C at atmospheric pressure, polytetrafluoroethylene exhibits a phase (denoted as IV), which has not been observed in P-V-T measurements at pressures above 10 Nm-2 (1 Kilobar). Data are presented to resolve this phase in the temperature range 0 to 50 °C and the pressure range 0 to 0.686 × 10 Nm-2. The II-IV (20 °C) transition pressure increases with temperature according to the equation P = ( 820 |