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, Ca3(PO4)2, is discussed. A solid-solution series between Cay P6O24 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

tures.

Extensive viscosity measurements by the fiber elongation method were made from 101 to 6 x 1014 poises. From this data a lower and more precise value of the activation energy (En = 72.3 kcal/mol) was obtained in the annealing range.

Resumé of values of the Faraday, W. J. Hamer, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 4, 435-439 (JulyAug. 1968).

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.

1

The heat of combustion of NBS Standard Sample 39i of benzoic acid under standard bomb conditions has been determined in terms of electrical units. A value of -26,434.0 J g1 was obtained. The total uncertainty in our determination is estimated to be ±3.3 J g1. The uncertainty due to random errors was 1.7 J g' and is based on the appropriate factors for the Student 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

+26.91 +0.68) × 105 and the IV-I (30 °C) transition according to the equation P = ( − 91 - 57.81 + 1.9912) × 105 suggesting a possible triple point near 2.6 × 108 Nm-2 and 54 °C. However, the IV-I transition probably cannot be resolved by volume measurements at pressures above 2 × 108 Nm-2 because its volume of transition is small and the two transitions overlap. The enthalpies of the transitions are calculated for different pressures and some thermodynamic properties of phase IV are determined indirectly. It is shown that, if the effect of volume change is subtracted, random reversals of the hand of the helical conformation of the molecule can account for appreciable fractions of the enthalpy and corresponding entropy change for the combined transitions at atmospheric pressure.

Electrostatic potentials and their spatial derivatives about point defects in ionic crystals, H. S. Bennett, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 5, 471-475 (Sept.-Oct. 1968).

Key words: CaF2; classical ionic lattice theory; electrostatic potential; lattice distortion; NaCl; point defect.

The electrostatic potential which arises from a lattice array of point ions is computed in terms of a Taylor's series expansion for small distances from a lattice site. This expansion gives the change in electrostatic energy when an ion moves in the background of a perfect point ion lattice potential. The Taylor's series coefficients for terms up to fourth order in the ion displacement are evaluated for the NaCl and CaF, lattice struc

tures.

Electric fields produced by a charge density in ionic crystals, H. S.
Bennett, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and
Chem.), No. 5, 475-478 (Sept.-Oct. 1968).

Key words: CaF; dipole shell coefficient; electric fields;
NaCl; polarization; spatially extended defects.

Spatially extended defects such as the F center give rise to an effective defect charge density which may produce important polarizations in the crystal. The electric field in the crystal depends upon these induced dipoles. Lattice summations for the contribution to the electric field which arises from ionic shells centered about the defect are evaluated for the NaCl and CaF lattice structures.

Mass spectrometric study of the photoionization of some fluorocarbons and trifluoromethyl halides, C. J. Noutary, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 5, 479-485 (Sept.-Oct. 1968).

Key words: CF4; C2F6; C3F8; C4F10; CFH; CF1Cl; CF3Br; CFI; heats of formation; ionization energies; mass spectrometric; photoionization; vacuum ultraviolet.

The photoionization curves and the threshold energies for the molecule and several abundant fragment ions of CF, C2F6, CaFs, CF10, CFH, CFCI, CF, Br, and CFI have been measured. The threshold energies are correlated and the ionic heats of formation and some bond dissociation energies are calculated. It is apparent that the values obtained for the CF3* ions are not the adiabatic ones, but include large amounts of excess energy. This excess is the lowest for the CF from CFI for which an explanation is suggested. Assuming that the excess is not zero for the last compound we obtain the following upper limits: AHƒ%°(CF3)* ≤+ 365.3 kJ mol−1=+87.3 kcal mol-1; I(CF3)* ≤ 8.62 eV; I(C2Fs)* ≤ 8.72 eV; I(C3F7)* ≤ 8.70 eV ; I(C4F9)* ≤8.68 eV. From the mean value D(C,p − Cp) = 402 ± 2 kJ mol1= 96.0 ±0.5 kcal mol-1 the bond dissociation energies D(C,Cs) = 363 ± 3 kJ mol-1 = 86.8 ± 0.8 kcal mol-1 and D(C, — C,) = 337 ± 4 kJ mol 1 = 80.6 ± 1.0 kcal mol-1 and D(C, − F) = 525 kJ mol-1125.7 kcal mol-1 are calculated.

1

Infrared matrix spectra of lithium fluoride, S. Abramowitz and N. Acquista, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 5, 487-493 (Sept.-Oct. 1968).

Key words: Force field; infrared; lithium fluoride dimer; low temperature; matrix; vibrational assignment. Evidence for a linear dimer LiF has been obtained by extending the spectral measurements for matrix isolated lithium fluoride into the far infrared region. The vapors from solid "LiF, 'LiF, and "LiF/LiF mixtures were deposited in argon matrices at liquid hydrogen temperatures. Vibrational assignments were made on the basis of the following linear species: Liz F2, "Liz F2, 6.7 Li, F2 and 7,6Li, F. Although the specific geometry of the dimer could not be determined, a normal coordinate analysis supported the spectral interpretation of a linear structure (C xv). Electronic transition moment integrals for first ionization of CO and the A-X transition in CO*. Some limitations on the use of the r-centroid approximation, P. H. Krupenie and W. Benesch, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 5,495-503 (Sept.-Oct. 1968).

2

Key words: CO; CO+; electronic transition moment integrals; Franck-Condon factors; Franck-Condon principle; transition probabilities.

Integrals necessary for the determination of transition moment matrix elements from experimental data have been evaluated numerically by use of vibrational wave functions derived from RKR potentials. A power series expansion for the electronic transition moment has been assumed. The significant quantities which can be related to an arbitrary center of expansion are vibrational overlap integrals and quantities of the form "v" dr. Experimental band intensities and relative populations for vibrational levels of the initial electronic state are needed to determine the expansion coefficients. Transition moment integrals have been calculated for first ionization from the ground electronic state of CO and for the A'II, - XE+ transition of CO. Comparison of these integrals with previous calculations based on Morse functions has shown them to be rather sensitive to the wave-functions [potentials] used. Characteristics generally attributed to the r-centroid and related integrals are examined, and some limitations on the use of the r-centroid approximation are discussed, following a review of assumptions made in the use of that approximation.

The configurations 3d4p in doubly ionized atoms of the iron group, C. Roth, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 5, 505-520 (Sept.-Oct. 1968).

Key words: BQ and T corrections; configurations 3d"4p; energy levels; interaction parameters; iron group; third spectra.

Experimental levels of the configurations 3d4p in the third spectra of the iron group were compared with corresponding calculated values. Besides the electrostatic and spin-orbit interactions the aLL + 1), BQ and T corrections were considered in the individual and general treatments. The insertion of the parameters B and T improved the results by about 25 percent. The root-mean-square (rms) error on fitting 581 experimental levels by means of 21 free interaction parameters was 138 cm-1. Altogether 912 energy levels were predicted.

Electron impact excitation of hydrogen Lyman-ɑ radiation, R. L. Long, Jr., D. M. Cox, and S. J. Smith, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 5, 521-535 (Sept.-Oct. 1968).

Key words: Atomic hydrogen; beams; electron impact excitation; experimental; high vacuum; Lyman-a.

An experimental investigation of electron impact excitation of the 2p state of atomic hydrogen is described. A beam of elec

trons was passed through a chopped beam of hydrogen atoms in a high vacuum apparatus. The modulated flux of Lyman-a photons emitted in the radiative decay of the 2p state was taken as a measurement of the excitation probability resulting from direct excitation plus indirect excitation resulting from cascading. The region surrounding the intersection of the two beams was electrically and magnetically shielded to prevent quenching of metastable 2s atoms and thereby to ensure that the observed Lyman-a flux resulted from decay of the short-lived 2p state. The experimental results are consistent with those obtained by Fite, Stebbings, and Brackmann [1959], and confirm the existence of a large discrepancy between theoretical and experimental results in the electron energy range below 50 eV.

November-December 1968

Interaction energy surfaces for Li(22S) and Li(22P) with H2, M. Krauss, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 6, 553-557 (Nov.-Dec. 1968).

Key words: Charge-transfer; energy surface; energy transfer; Hartree-Fock; H2(X1ƒ); Li(22P); Li(22S);

resonance state.

Interaction energy surfaces for the interaction of Li(22S) and Li(22P) with H2 are calculated using approximate Hartree-Fock trial functions. The crossing of energy curves is observed for C2v conformations if the H2 internuclear distance is sufficiently large. No crossing is observed for colinear collisions for any H2 distance.

The wave function of the strongly attractive state involved in the crossing is related to the metastable negative-ion states that are postulated to account for resonant electron-molecule scattering. Such a charge-transfer state can only be bound for C2v conformations for the H2 molecule. The likelihood and geometry of the crossing complexes for other molecules interacting with alkalis is discussed in terms of the formation of these resonance charge-transfer states.

Energy levels and classified lines in the first spectrum of technetium (Tc 1), W. R. Bozman, C. H. Corliss, and J. L. Tech. J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 6, 559-608 (Nov.-Dec. 1968).

Key words: Atomic spectra; energy levels, Tc 1; spectrum of technetium; technetium.

Progress in the classification of Tc 1 lines is reported. About 2200 of the known Tc 1 lines between 2154 and 8918 Å are now classified as transitions between 108 even and 147 odd energy levels. Tables of levels and classified lines are given.

The first spectrum of tungsten (W 1), D. D. Laun and C. H. Corliss, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.). No. 6, 609-755 (Nov.-Dec. 1968).

Key words: Atomic spectra; energy levels; spectroscopy; spectrum of tungsten; tungsten; wavelengths.

The first spectrum of tungsten (W 1) has been observed in the region between 2000 Å and 10500 Å. Of the 6800 spectral lines reported here, about 5500 have been classified as transitions between 91 even and 365 odd levels.

Theoretical interpretation of the even levels in the first spectrum of tungsten, Y. Shadmi and E. Caspi, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 6, 757-760 (Nov.-Dec. 1968).

Key words: Atomic spectrum, W 1; energy levels, W 1; spectrum of tungsten; tungsten; W 1.

The calculated even levels of W 1 up to the height of about 40,000 cm-1, which is the height of the ground level of the de

configuration, are reported. Fifty-seven observed levels are fitted to them, with a mean error of 100 cm-1. L-S coupling and configuration assignments are usually meaningless because of a between 108 even and 147 odd energy levels. very strong spinorbit interaction and configuration interaction. For every level, the largest squared L-S coupling components of its eigenvector are reported, as well as observed and calculated g-values. Stable carbon isotope ratio measurements with a gas density meter, S. P. Wasik and W. Tsang, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 6, 761-764 (Nov.-Dec. 1968).

Key words: Carbon-13; carbon dioxide; ethyl acetate; gas chromatography; gas density meter; isotope ratios.

A method is presented for measuring C13/C12 isotope ratio of organic compounds by burning the material in a stream of normal CO2, separating the combustion products by gas chromatog raphy and sequentially measuring the density of the enriched CO2 peak with a gas density meter. Data are presented for the analysis of enriched ethyl acetate from 15 to 1 percent enrichment. The method is applicable for other stable isotope analysis.

The single crystal spectrum of hexakis(imidazole)nickel(II)nitrate, C. W. Reimann, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 6, 765-768 (Nov.-Dec. 1968).

Key words: Crystal spectrum; hexakis(imidazole) nickel(II) nitrate; octahedral nickel(II); spin-forbidden bands. The crystal spectrum of hexakis(imidazole)nickel(II)nitrate from 7000 cm-1 to 30,000 cm-1 at liquid nitrogen temperature has been measured. Three spin-allowed and three spin-forbidden bands in this spectrum were assigned on the basis of octahedral ligand field symmetry. These assignments are compared with those made in several related materials. Important differences and similarities in spectral detail and their bearing on assignments in other strong field nickel(II) complexes, are discussed. Crystalline alpha and beta forms of 3-O-a-D-glucopyranosyl-Darabinopyranose, H. S. Isbell, H. L. Frush, and J. D. Moyer, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 6, 769-771 (Nov.-Dec. 1968).

Key words: Anomeric sugars; calcium maltobionate; maltose-1-1C; mutarotation of 3-O-a-D-glucopyranosyl-Darabinopyranose; Ruff degradation of; sugars; 3-O-a-D-glucopyranosyl-D-arabinopyranose.

Crystalline 3-0-a-D-glucopyranosyl-a-D-arabinopyranose monohydrate, mp 120 to 121 °C, and 3-C-a-D-glucopyranosylB-D-arabinopyranose, mp 155 to 157 °C, were prepared from a sirup obtained by the Ruff degradation of calcium maltobionate. For the alpha monohydrate, [a]20 + 16.7 x 10-0.0241 9.6 × 10-0.098+46.6, and for the anhydrous beta form, [a]20 -25.6 × 10-0.0251 - 9.4 x 10-0.097 +49.2. The structure of the sugar was established by converting it into maltose.

=

=

Treatment of the alpha form with pyridine-acetic anhydride gave a heptaacetate, mp 127 to 128 °C, [a]20+ 62.4° (c 2.5, chloroform). The beta form gave a heptaacetate, mp 194.5 195.5 °C, [a]20+ 13.4° (c 2.5, chloroform).

Preparation and solubility of hydroxyapatite, E. C. Moreno, T. M. Gregory, and W. E. Brown, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 6, 773-782 (Nov.-Dec. 1968).

Key words: Apatite; hydroxyapatite; calcium phosphates; solubility; solubility isotherms; solubility product. Two portions of a synthetic hydroxyapatite (HA), CaOH(PO4)3, fully characterized by x-ray, infrared, petrographic, and chemical analyses, were heated at 1,000 °C in air

and steam atmospheres, respectively. Solubility isotherms for these two samples in the system Ca(OH)2-H3PO4-H2O were determined in the pH range 5 to 7 by equilibrating the solids with dilute H3PO4 solutions. Both samples of HA dissolved stoichiometrically. The activity products (Ca++)5(OH−)(POF)3 and their standard errors-obtained by a least squares adjustment of the measurements (Ca and P concentrations and pH of the saturated solutions) subject to the conditions of electroneutrality, constancy of the activity product, and stoichiometric dissolution-were 3.73 ±0.5 x 10-58 for the steam-heated HA and 2.5, 0.4 x 10-55 for the air-heated HA. Allowance was made in the calculations for the presence of the ion pairs [CaHPO.] and [CaH2PO1]+. The higher solubility product for the air-heated HA is ascribed either to a change in the heat of formation brought about by partial dehydration or to a state of fine subdivision resulting from a disproportionation reaction. The solubility product constants were used to calculate the points of intersection (i.e., singular points) of the two HA solubility isotherms with the isotherms of CaHPO, 2H2O and CaHPO4; it was found that the pH's of the singular points for the

air-heated HA were a full unit higher than those of the steamheated preparation. Conditions are described for the precipitation of HA crystals suitable for solubility measurements.

High temperature dehydroxylation of apatitic phosphates, T. Negas and R. S. Roth, J. Res. Nat. Bur. Stand. (U.S.), 72A (Phys. and Chem.), No. 6, 783-787 (Nov.-Dec. 1968).

Key words: Apatite; dehydroxylation; high temperature; phosphates; x-ray diffraction.

Sг10P6O24(OH)2, (Hex. a = 9.765 Å, c = 7.280 Å), and Ba10P 6024(OH)2, (Hex. a = 10.177 Å, c = 7.731 Å), undergo cell parameter contractions at elevated temperatures in air. These can be correlated with progressive dehydroxylation, although neither can be completely dehydrated. Pb10P6O24(OH)2, (Hex. a = 9.878 Å, c = 7.432 Å), also does not completely dehydrate in

air.

A new apatite-like strontium phosphate, (Hex. a=9.872 Å, c=7.199 Å), was prepared at elevated temperatures in vacuum.

January-February 1969

Specific heats of oxygen at coexistence, R. D. Goodwin and L. A. Weber, J. Res. Nat. Bur. Stand. (U.S.), 73A (Phys. and Chem.), No. 1, 1-13 (Jan.-Feb. 1969).

Key words: Coexistence; experimental; heat capacity; liquid phase; oxygen; saturated liquid; specific heat. Specific heats of saturated liquid, along the coexistence path, are useful for computing thermodynamic properties throughout the compressed liquid phase. We report 86 experimental heat capacities of oxygen for the two-phase system, liquid plus vapor, from the triple-point to near the critical-point and corresponding derived values for the liquid phase. These results are represented by a formula which can be integrated for heat absorbed and for entropy. The changes in value of internal energy, enthalpy, and entropy of the saturated liquid are tabulated from the triple-point to the critical-point.

Specific heats C, of fluid oxygen from the triple point to 300 K at pressures to 350 atmospheres, R. D. Goodwin and L. A. Weber, J. Res. Nat. Bur. Stand. (U.S.), 73A (Phys. and Chem.), No. 1, 15-24 (Jan.-Feb. 1969).

Key words: Compressed liquid; heat capacities; liquid; oxygen; specific heats; thermodynamic properties.

Experimental specific heats at constant volume for oxygen in single phase domains are reported from the triple point to 300 K at pressures to 350 atmospheres. An empirical equation with seven constants describes these specific heats over the entire domain of p-T coordinates to within the experimental accuracy of 1 to 2 percent. Values for the terminal slopes of PVT isochores at the coexistence boundary, (a P/aT), are derived for the liquid.

Thermodynamic properties of fluid oxygen at temperatures to 250 K and pressures to 350 atmospheres on isochores at 1.3 to 3.0 times critical density, R. D. Goodwin, J. Res. Nat. Bur. Stand. (U.S.), 73A (Phys. and Chem.), No. 1, 25-36 (Jan.-Feb. 1969).

Key words: Compressed liquid; enthalpy; entropy; internal energy; oxygen; saturated liquid; thermodynamic properties.

The starting point for these calculations is liquid oxygen at the triple point. An analytical formula is used for specific heats of saturated liquid along the coexistence path to obtain internal energies and entropies of the saturated liquid. With these initial values, the calculations next are made as a function of temperature along isochores, using an "equation of state" for the specific heats Cup, T) in the single-phase domain. Enthalpies are obtained by adding Pv to the internal energies. Results are tabulated at uniform densities and temperatures. Based on uncertainties of one percent in the specific heat data, the uncertainty of thermal properties also is taken to be 1 percent.

Two new standards for the pH scale, B. R. Staples and R. G. Bates, J. Res. Nat. Bur. Stand. (U.S.), 73A (Phys. and Chem.), No. 1, 37-41 (Jan.-Feb. 1969).

Key words: Acidity; carbonate; citrate; emf; hydrogen electrode; pH; standards for pH.

Two new primary standards for the NBS pH scale, supplementing the five already available, are proposed. The new reference solutions are the 0.05 molal solution of potassium dihydrogen citrate and a mixture of sodium bicarbonate and sodium carbonate, each 0.025 molal. The citrate solution has a pH of 3.776 at 25 °C and is more stable under certain conditions than either the tartrate or phthalate standards. The carbonate solution has a pH of 10.012 at 25 °C. It therefore extends the NBS pH scale above its present upper limit of 9.180 at this temperature. Reference values pH(S), based on emf measurements of cells with hydrogen electrodes and silver-silver chloride electrodes, have been assigned to these two standard solutions at 11 temperatures from 0 to 50 °C.

Calculation of diffusion coefficients in ternary systems from diaphragm cell experiments, P. R. Patel, E. C. Moreno, and T. M. Gregory, J. Res. Nat. Bur. Stand. (U.S.), 73A (Phys. and Chem.), No. 1, 43-49 (Jan.-Feb. 1969).

Key words: Diaphragm cell; diffusion coefficients; least squares calculation; ternary system.

Using a generalized least square procedure, a method is developed to estimate diffusion coefficients, Dij, from concentration measurements made in a set of experiments of varying duration but with the same initial conditions. The method requires neither approximations nor restrictions in the flow equations. The D1 and their errors are calculated simultaneously with the adjustment of the weighted observables-concentrations of the two solute components and time. A procedure is described to insure convergence in a given experimental set. The effect of the duration of the longest experiment, and errors in the observables on the estimated values of D1, and their errors, are investigated. Application of the method to available data yielded values for Dij in agreement with those previously calculated by more involved procedures.

Calculated line strengths for the transition array (3ď3 + 3d24s) = 3d24p in Ti 11, H. Mendlowitz, J. Res. Nat. Bur. Stand. (U.S.), 73A (Phys. and Chem.), No. 1, 51-64 (Jan.-Feb. 1969).

Key words: Calculated line strengths; configuration interaction; intermediate coupling; Ti 11; 3d3, 3d24s, 3d24p configurations; transition array.

The transition array for the transitions between the configurations (3d3+3d24s) and 3d24p in Ti 11 are presented here. The relative line strengths have been calculated in the intermediate coupling scheme, taking into account interaction between configurations. The relative phase and magnitude of the radial transition integrals (s-p) and (d-p) for the jumping electron in the LS coupling have been determined empirically.

Morphological stability of a cylinder, S. R. Coriell and S. C. Hardy, J. Res. Nat. Bur. Stand. (U.S.), 73A (Phys. and Chem.), No. 1, 65-68 (Jan.-Feb. 1969).

Key words: Cylinder; ice; interface kinetics; morphological stability; solute diffusion; surface tension.

The stability of the shape of a solid cylinder crystallizing in a supercooled liquid is treated. The effects of solute diffusion, slightly anisotropic surface tension and interface kinetics are included. The resulting stability equations are applied to the specific case of ice cylinders.