are Mg/24Mg=0.12663 ± 0.00013 and Mg/24Mg=0.13932 0.00026, yielding an atomic weight (12C = 12) of 24.30497 ± 0.00044. The indicated uncertainties are overall limits of error based on 95 percent confidence limits for the mean and allowances for effects of known sources of possible systematic

error.

Mass spectrometric study of photoionization, V. Water and ammonia, V. H. Dibeler, J. A. Walker, and H. M. Rosenstock, J. Res. NBS 70A6-417, pp. 459-463 (Nov.-Dec. 1966).

Key words: Autoionization; electronic; excited states; H2O*; NH ̧*; NH2+: OH+ ions; heats of formation; ionization thresholds; mass spectrometer; photoionization; radicals; Rydberg levels; vacuum monochromators. Photoionization efficiency curves are obtained for the molecule and fragment ions of H2O and NH, in the wavelength region extending from onset of ionization to 600 A. Threshold values of 12.593eV and 10.162eV are observed for the H2O+ and NH+ ions, respectively. Vibrationally excited states of the molecule ions and autoionization of Rydberg levels are observed. A determination of the bond angle of the H2O+ ion from the Franck-Condon factors of the bending overtones results in a value of 112 degrees. Threshold values of the fragment ions permit calculations of heats of formation of the OH and NH+ ions and result in the ionization energies, I(OH)=12.94eV and I(NH2)=11.22eV.

Interpretation of the third spectrum of gold (Au 111), L. Iglesias, J. Res. NBS 70A6-418, pp. 465-466 (Nov.-Dec. 1966).

Key words: Corrections to analysis of Au III; gold; spectrum of Au III; third spectrum.

A revision of the analysis of the Au III spectrum is presented. Of 9 energy levels considered doubtful on the basis of a recent theoretical treatment, 6 are found to be real and 3 have been rejected as incorrect. Three new energy levels have also been found in agreement with theoretical predictions.

A formal solution for slit corrections in small-angle x-ray scattering, J. Mazur and A. M. Wims, J. Res. NBS 70A6-419, pp. 467-471 (Nov.-Dec. 1966).

Key words: Distribution of intensity; integral equation; scattering cross section; slit correction; small-angle x-ray scattering.

Slit shaped apertures are usually used in small-angle x-ray scattering measurements in order to obtain easily measured intensities of scattered radiation. As a result, the scattering intensity at a given angle determined by the camera, the center of the sample, and the central incident x-ray beam is not simply related to the scattering from the sample only at that angle. The experimentally determined intensities I(x) are related to the true scattering intensities by the following integral equation:

in

The direct replacement of aromatic fluorine hexafluorobenzene has hitherto been possible only by the use of nucleophilic reagents. In this investigation, the replacement of nuclear fluorine by nonnucleophilic, or weakly nucleophilic, reagents was achieved by reaction at relatively high temperatures, 300 to 850 °C. For example, the reaction of hexafluorobenzene with such reagents as bromine, chlorine, and tetrafluoroethylene gave as major products bromopentafluorobenezene, chloropentafluorobenzene, and octafluorotoluene. In addition, pentafluorohalobenzenes can also be produced by passage of hexafluorobenzene over the appropriate alkali or alkaline earth-metal halides at elevated temperatures.

The mechanism of the pyrolytic reactions of hexafluorobenzene and the nonionic coreactants are considered to involve free-radical intermediates. The reaction of hexafluorobenzene with the ionic coreactants may proceed by an ionic mechanism similar to that advanced for the usual, relatively low temperature, nucleophilic substitution reactions of aromatic systems. However, a more complicated free radical-ionic process cannot be ruled out for these reactions.

The melting temperatures of the n-paraffins and the convergence temperature for polyethylene, M. G. Broadhurst, J. Res. NBS 70A6-421, pp. 481-486 (Nov.-Dec. 1966).

Key words: Convergence temperature; melting temperatures; methyl surfaces; n-paraffins; polyethylene; thermodynamic properties.

The extrapolation of the melting points, Tm, of the n-paraffins to large chain lengths (n→ ∞) is reexamined in order to resolve the differences in the proposed values of the convergence temperature To= lim T. Experimental liquid entropies can be made consistent with a term, R In n, proposed by Flory and Vrij. This term effectively replaces the well-known expression Tm=To(n+a)/(n+b) with an expression Tm= To(n+a)/(n+ In n+b); thus, slowing the convergence rate and increasing To from 141.1 °C to 144.7 °C. Independent estimates of the parameters in the melting relationship were obtained from thermodynamic data and the least squares estimate of T=144.7 °C (calculated from 33 melting points with a standard deviation of T=0.3 °C) could not be altered by more than ±0.5 °C by any reasonable variation of the parameters. A simplified melting expression is obtained for polyethylene which includes both the chain end and fold surface energies, and it is shown that chain end effects partly account for the discrepancy between the 144.7 °C convergence temperature and experimental melting temperatures (~139 °C) of extended chain polyethylene crystals.

General treatment of the thermogravimetry of polymers, J. H. Flynn and L. A. Wall, J. Res. NBS 70A6-422, pp. 487-523 (Nov.-Dec. 1966).

Key words: Degradation; nonisothermal kinetics; polymers; pyrolysis: thermal decomposition; thermogravimetry; thermolysis; stability of polymers.

Theoretical equations are developed for typical decompositions of polymers including those in which the volatilization does not follow a simple "reaction order" and those made up of a composite of several reactions of differing energies of activation. The effects of order, activation energy, heating rate and temperature dependence upon the calculated thermograms is illustrated. The literature on thermogravimetric kinetics is critically reviewed and coalesced into a logical and coherent development stressing the interrelation of methods and employing a consistent system of notation. As a result, a number of improved methods and new methods for the analysis of kinetic data applicable to the complex systems mentioned above are developed. It is concluded that methods involving a variable rate of heating or involving several thermogravimetric traces at

different rates of heating are capable of establishing the uniqueness of kinetic parameters. A new method of determining initial parameters from rate-conversion data is developed. A novel concept is employed of programming reaction variables (in this case, the heating rate) in a manner which greatly simplifies the mathematics of the kinetic system and which shows promise of a wide range of applicability in the area of rate processes. Viscoelastic behavior under large deformations, L. J. Zapas, J. Res. NBS 70A6-423, pp. 525-532 (Nov.-Dec. 1966).

Key words: BKZ theory; constant rate of strain; creep; elastic fluid; nonlinear behavior; polyisobutylene; recovery; stress; relaxation.

The BKZ elastic fluid theory is used to correlate experimental results obtained in biaxial strain and steady simple shear. With a heuristic potential function involving three material properties, excellent agreement is obtained between theory and experiment. In the special case where one of the material properties is dominant, the behavior in steady simple shear is calculated from dynamic measurements in the infinitesimal range and is compared with actual data.

Statistical aspects of second and third law heats, W. S. Horton, J. Res. NBS 70A6-424, pp. 533-539, (Nov.-Dec. 1966).

Key words: Bias of least squares estimators; coefficient of variation; correlated estimators; enthalpy adjustments; heat of vaporization; high temperature chemistry; overestimation of standard deviation; second law heat; slope estimators; third law heat; vapor pressure.

The effects of random errors and of nonconstant heat of vaporization upon the estimation of the second and third law heats of vaporization are examined. The most important conclusion is that the often noticed marked improvement in precision of the third law heat over that for the second law heat is real and is a natural consequence of the difference between the two estimators. The effects of systematic errors upon the two heats are not investigated here. Other results of interest, but of less importance because of the small magnitude of the effects, include: (1) the two heats are negatively correlated, (2) the second law heat is generally biased, (3) the third law heat is not the minimum variance unbiased estimator of the heat of vaporization, and (4) the standard deviation obtained from least squares fitting consistently overestimates the true standard deviation, but by a negligible amount. Any reversible process for which the equilibrium constant is treated by a similar procedure is governed by the same considerations. The results apply approximately at any temperature although the stimulus for these considerations comes from high temperature chemistry. Density-temperature formulae for coexisting liquid and vapor and for freezing liquid parahydrogen, R. D. Goodwin, J. Res. NBS 70A6-425, pp. 541-544 (Nov.-Dec. 1966).

Key words: Coexistence densities; freezing liquid densities; hydrogen; melting-line liquid densities; orthobaric densities; parahydrogen; vapor-liquid equilibrium.

A single formula is given for coexistence temperature as a continuous function of the vapor-liquid densities. With six coefficients and seven adjusted exponents, it may conveniently replace the several formulae formerly used in separate regions of the data. Freezing liquid densities are described by a simple power law in temperature, replacing more complicated formulae. Computed results are tabulated and compared with the derived data.

Solubility of CaHPO, 2H2O and formation of ion pairs in the system Ca(OH)2-H3PO4-H2O at 37.5 °C, E. C. Moreno, T. M. Gregory and W. E. Brown, J. Res. NBS 70A6-426, pp. 545552 (Nov.-Dec. 1966).

Key words: Solubility of calcium monohydrogen phosphate dihydrate at 37.5 °C; calcium-phosphate ion-pairs; solubility of dicalcium phosphate dihydrate; solubility of dibasic calcium phosphate dihydrate.

The solubility isotherm for CaHPO,‍2H2O (DCPD) in the three-component system Ca(OH)2-H3PO4-H2O was determined in the pH range 3.5 to 6.8 by leaching a thermostated column of DCPD with dilute phosphoric acid solutions. In confirmatory experiments, equilibrium was approached both from super- and under-saturation by shaking DCPD with appropriate solutions. The calculated ionic activity product (Ca++)× (HPO1"), appeared to be a parabolic function of pH with a minimum near pH 5.0. The pH dependence of the ionic product could be accounted for by considering the ion pairs [CaHPO4]° and [CaH2PO4] as semi-empirical parameters. Under the condition of saturation with respect to DCPD, the activity of the pair [CaHPO.] must be a constant. The activity of the species [CaH2PO4] was shown to vary directly with hydrogen ion activity. The activities of the two ion pairs were adjusted to give a set of pH-independent ionic activity products with a mean of 2.19±0.11×10-7. The stability constants for [CaHPO.] and [CaH2PO4] are 5.88 ± 0.031 x 102 and 7.49 ± 0.039, respectively. Experiments were conducted to study the hydrolysis of DCPD to more basic calcium phosphates and the kinetics of these transformations is discussed. The significance of the ion pairs in human serum is considered.

Dissociation of some substituted phenols in 50-percent aqueous methanol as solvent, R. A. Robinson and R. G. Bates, J. Res. NBS 70A6-427, pp. 553-556 (Nov.-Dec. 1966).

Key words: Dissociation constant; methanol-water mixtures; solvent effects; substituted phenols.

The dissociation constants of the following substituted phenols in 50 wt percent methanol have been measured at 25 °C: o-nitrophenol, p-nitrophenol, 4-methyl-2-nitrophenol, 2, 6dichlorophenol, pentachlorophenol. The respective values found, expressed as pK values, are 7.917, 7.692, 8.284, 7.680, and 5.27. The dissociation constants of 4-methyl-2-nitrophenol and pentachlorophenol, again expressed as pK values, have been measured in water as solvent at 25 °C and found to be 7.59, and 4.820, respectively.

January-February 1967

Electric fields produced in cubic crystals by point defects, A. D. Franklin and D. J. Sparks, J. Res. NBS 71A1-428, pp. 1-2 (Jan.-Feb. 1967).

Key words: Electric fields; ionic crystals; lattice sums; point defects; polarization; NaCl; CsCl; CaF2; ZnS.

Charged point defects in crystals polarize the surrounding ions. These induced dipoles contribute to the electric field in the crystal. In this paper, lattice sums for the calculation of this contribution are given for the NaCl, CsCl, CaF2, and ZnS structures. Various positions for the defect are chosen, and the field evaluated near lattice sites in the vicinity of the defect, with radial (with respect to the defect) displacements of ±20 percent of the cation-anion distance allowed away from each lattice site. The lattice sums are expressed in power series, including terms up to cubic in the displacements, and the coefficients tabulated.

Heat capacity and thermodynamic properties of beryllium 1:3aluminate, BeO 3Al2O3, from 15 to 390 °K, G. T. Furukawa and W. G. Saba, J. Res. NBS 71A1-429, pp.3-8 (Jan.-Feb. 1967).

Key words: Beryllium 1:3-aluminate; enthalpy; entropy; Gibbs energy; heat capacity; low temperature calorimetry; thermodynamic properties.

The heat capacity of beryllium 1:3-aluminate, BeO 3 Al2O3, was determined from 15 to 380 °K and the thermodynamic properties calculated from 0 to 390 °K. The entropy at 298.15 °K was found to be 175.55 J deg1 mol1 (41.96 cal deg1 mol·1). Dissociation constant of m-nitrophenol in 50 wt percent methanolwater solvent from 25 to 40 °C and related medium effects, B. J. Steel, R. A. Robinson, and R. G. Bates, J. Res. NBS 71A1430, pp. 9-12 (Jan.-Feb. 1967).

Key words: Dissociation; electrolytes; methanol; mnitrophenol; nonaqueous solvents; phenols; thermodynamics.

The dissociation constant of m-nitrophenol in 50 wt percent methanol-water as solvent has been determined at 25, 30, 35, and 40 °C. A spectrophotometric method was used, together with acidity functions for buffer solutions in 50 percent methanol derived from previous emf measurements. Values of the enthalpy and entropy changes on dissociation of the phenol have been calculated. A comparison with corresponding values for the dissociation of m-nitrophenol in aqueous solution affords a measure of the medium effects. The medium effect for mnitrophenol lies intermediate between that for o-nitrophenol and that for p-nitrophenol.

On the calculation of moments of molecular weight distribution from sedimentation equilibrium data, I. H. Billick, M. Schultz, and G. H. Weiss, J. Res. NBS 71A1-431, pp. 13-17 (Jan.-Feb. 1967).

Key words: Molecular weight average; molecular weight distributions; moments: polydispersity; polynomial representation; sedimentation equilibrium.

In this paper we discuss a technique for calculating moments

of polydisperse materials in terms of concentration readings along the cell. The proposed method minimizes dependence on data from the end points where they may be unreliable. An analysis is given of the errors involved in the use of the proposed method when the underlying molecular weight distribution is the Schulz distribution or the lognormal.

The far infrared spectrum of vulcanized natural rubber, J. E. Stewart and F. J. Linnig, J. Res. NBS 71A1-432, pp. 19-23 (Jan.-Feb. 1967).

Key words: Accelerators; far infrared; natural rubber; sulfur; tetramethylthiuram disulfide; vulcanization; zinc dibutyldithiocarbamate; zinc dimethyldithiocarbamate.

Earlier studies of the infrared spectra of rubber and some vulcanizates of rubber have been extended into the 650 to 33 cm-1 far infrared region. Some of the absorption bands originating in the crystalline portion of unvulcanized rubber have been studied by using polarized radiation and samples oriented by stretching. Vulcanization of rubber with sulfur alone produces a general weakening of all absorption bands and no new absorptions. Vulcanization with sulfur and an accelerator also results in a reduction in intensity of the rubber absorptions, but is accompanied by the appearance of new bands. When the accelerator is tetramethylthiuram disulfide (TMTD) the new bands are probably indicative of a thiocarbamate structure. When zinc dibutyldithiocarbamate is used as an accelerator a band probably due to zinc sulfide occurs. Vulcanization with TMTD alone produces only slight changes in the far infrared spectrum. However, when TMTD is used in the presence of zinc oxide a reaction occurs in which zinc dimethyldithiocarbamate (ZnDMDC) is formed. After vulcanization for a short period of time strong TMTD bands remain, but after long vulcanization the TMTD bands are replaced by ZnDMDC bands.

Irradiation of dextran and its aqueous solutions with cobalt-60 gamma rays, J. H. Flynn, L. A. Wall, and W. L. Morrow, J. Res. NBS 71A1-433, pp. 25-31 (Jan.-Feb. 1967).

Key words: Aqueous solution; cross-linking; dextran; dextran triacetate; gamma irradiation; polymer degradation; postirradiative decay.

Cross-linking predominates over chain scission during the irradiation of concentrated aqueous dextran solutions by cobalt60 gamma rays in the absence of oxygen. An extensive and longlived postirradiative viscosity decay, which has not been previously reported, is attributed to the agency of hydrogen peroxide formed during the radiolysis of water. Solid dextran primarily degrades upon y-irradiation while dextran triacetate is borderline between dominant scission and cross-linking. Both exhibit a postirradiative viscosity decrease when irradiated in the presence of water vapor. Electron spin resonance spectra of dextran in the solid state and in aqueous solution are presented and compared. Spin resonance spectral and chemical evidence concerning the mechanism of cross-linking and postirradiative decay reactions is presented. There is conflicting evidence for the presence of oxyradicals. Speculations are made concerning possible mechanisms of oxyradical formation and their role in the production of ether and peroxy linkages.

Synthesis of poly-p-oxyperfluorobenzylene and related polymers. A novel synthesis of the monomer 2,3,5,6-tetrafluoro-4-trifluoromethylphenol, J. M. Antonucci and L. A. Wall, J. Res. NBS 71A1-434, pp. 33-41 (Jan.-Feb. 1967).

Key words:

1-1-butoxy-2,3,5,6-tetrafluoro-4-trifluoromethylbenzene; perfluoro-p-quinone methide; polymerization; poly-p-oxyperfluorobenzylene; pyrolysis; 2,3,5,6tetrafluoro-4-trifluoromethylphenol.

The synthesis and polymerization of 2,3,5,6-tetrafluoro-4trifluoromethylphenol (heptafluoro-p-cresol) is described. The polymer, poly-p-oxyperfluorobenzylene (polyperfluoro-pbenzylene oxide), is probably formed through the perfluoro-pquinonemethide intermediate obtained by the intramolecular loss of either hydrogen fluoride or a metal fluoride. The polymer has a structure analogous to that reported for the polymer derived from p-trifluoromethylphenol under similar conditions.

In the course of the synthesis of the monomer, heptafluoro-pcresol, a novel synthetic method was discovered. The synthesis consists in the prior preparation of 1-1-butoxy-2,3,5,6tetrafluoro-4-trifluoromethylbenzene and its subsequent thermal decomposition into the isobutylene and the desired cresol. Similarly, N-t-butyl-2,3,5,6-tetrafluoro-4-trifluoromethylaniline undergoes a similar liquid phase pyrolysis into isobutylene and 2,3,5,6,-tetrafluoro-4-trifluoromethylaniline. However, during

the course of this pyrolysis, practically all of the aniline undergoes polymerization with concomitant loss of hydrogen fluoride. The polymer is formed by the same mechanism operative in the thermal polymerization of p-heptafluorocresol except that additional quantities of hydrogen fluoride can be eliminated from the -NHCF2- segments of the polymer chain thereby introducing -N=CF- units into the polymer backbone.

Other t-butyl derivatives were synthesized and their thermal decomposition studied. Several possible mechanisms for the decomposition of these t-butyl compounds are considered. Preparation, purity, and homogeneity of NBS standard samples 705 and 706, polystyrene, D. McIntyre, J. Res. NBS 71A1435, pp. 43-47 (Jan.-Feb. 1967).

Key words: Ash content; elemental analysis; homogeneity; lithium content; molecular weights; polymer; preparation; purity; sampling; standard sample; volatile content.

The state-of-art in the measurement of the molecular weights of macromolecules is discussed. The preparation of polystyrene standard samples 705 and 706 is described. The results and the description of the carbon-hydrogen microanalysis, the ash determination, the lithium analysis, and the volatiles determination are given. The sampling methods for determining the homogeneity of 705 and 706 are presented. Some evidence of heterogeneity appeared to be present, particularly for lot 705, but the experiment did not provide conclusive evidence of heterogeneity of the material.

Large-scale, preparative paper chromatography, H. L. Frush, J. Res. NBS 71A1-436, pp. 49-52 (Jan.-Feb. 1967).

Key words: Chromatography on seed-test paper, large-scale paper chromatography; radioactive carbohydrates; use of heavy papers in preparative chromatography.

S. Cerezo, V. Deulofeu, and A. Cohen, J. Res. NBS 71A1437, pp. 53-79 (Jan.-Feb. 1967).

Key words: Absorption spectra; acyclic sugars; 1acylamido sugars; aldofuranoid sugars; aldopyranoid sugars; infrared spectra.

The infrared absorption spectra of two glycofuranosylacetamides and their perbenzoates, and of eleven glycopyranosylacylamides and eight esters thereof, are presented and discussed. For comparison, the spectra of thirteen 1,1-bis(acylamido)-1-deoxyalditols and eight esters thereof are also given and

discussed.

The useful correlations between structure and infrared absorption made by Barker and co-workers for certain carbohydrates, and by Nanasi and co-workers for some Narylglycosylamines, cannot be extended to the 1-acylamido compounds we have studied. Certain of Verstraeten's correlations may have some diagnostic value.

March-April 1967

Relative enthalpy of beryllium 1:1-aluminate, BeO Al2O3, from 273 to 1173 °K. Thermodynamic properties from 273 to 2150 °K, D. A. Ditmars and T. B. Douglas, J. Res. NBS 71A2-438, pp. 89-95 (Mar.-Apr. 1967).

Key words: Beryllium aluminate; chrysoberyl; drop calorimetry; enthalpy measurements; high-temperature calorimetry; mixed oxides; specific heat; thermc dynamic properties.

The relative enthalpy of the beryllium aluminate BeO.Al2O, was measured by "drop" calorimetry from 273 to 1173 °K. The thermodynamic properties were calculated up to 2150 °K (approximately the melting point). For this calculation, the data were extrapolated above 1173 °K and the entropy at 273 °K, previously determined at the NBS, was used.

to

Key words: Beryllium aluminate (1:3); drop calorimetry; enthalpy measurements; high-temperature calorimetry; mixed oxides; specific heat; thermodynamic properties. The relative enthalpy of beryllium 1:3-aluminate, BeO 3 Al2O3, was measured from 273 1173 °K. Thermodynamic properties were calculated up to 2150 °K (near the melting point) by extrapolating the present measurements and making them consistent with existing low-temperature data. The heats of combustion of polytetrafluoroethylene (Teflon) and graphite in elemental fluorine, E. S. Domalski and G. T. Armstrong, J. Res. NBS 71A2-440, pp. 105-118 (Mar.-Apr. 1967).

Key words: Aluminum fluoride: carbon tetrafluoride; fluorine; fluorine bomb calorimetry; graphite, heat of combustion; heat of formation; hydrogen fluoride aqueous; Teflon.

Bomb calorimetric measurements are reported for the combustion in fluorine of polytetrafluoroethylene (Teflon) and graphite-polytetrafluoroethylene mixtures. Mass spectrometric examination of the product gases showed CF, to be the only major product with CF.(g) present in only very small amounts. The completeness of combustion of the graphite was determined by chemical analysis of combustion residues and found to range from 97 to better than 99 percent. From the combustion data, the heats of formation AH °298[CF,(g)] and AH °298[C2F4 (solid

polymer)] were determined to be -222.87±0.38 kcal mol-1 and -197.82±0.39 kcal (gfw C2F1)-', respectively. The uncertainties are estimates of the overall experimental errors.

A previously reported value for the heat of formation of AlF3(c) is adjusted to be consistent with the present work. An evaluation of other data on CF, is presented. The heat of formation of CF,(g) is combined with other work to derive the heats of formation of HF solutions at three specific concentrations.

Phase relations in the systems TiO2-IrO2 and SnO2-IrO2 in air, C. L. McDaniel and S. J. Schneider, J. Res. NBS 71A2-441, pp. 119-123 (Mar.-Apr. 1967).

Key words: Dissociation; phase relations; SnO2-IrO2 system; solid solution; TiO2-IrO2 system.

The pseudobinary systems TiO2-IrO2 and SnO2-IrO2 were studied by x-ray diffraction after treatment at various temperatures in air. Their equilibrium phase diagrams were similar, with no intermediate phases detected in either system. Maximum solid solution of TiO2 occurs with the addition of about 5 mole percent IrO2 at 1040 °C. Solid solution of TiO2 in IrO, extends to a maximum of about 12 mole percent TiO2 at 1040 °C, the dissociation temperature. Limited solid solubility of SnO2 in IrO2 exists up to 3 mole percent SnO2 at the dissociation temperature, 1025 °C. Solid solution in SnO2 was not detected at temperatures up to 1400 °C.

Sample purity and the N.Q.R. of Cμ35 in KCIO, at 0 °C, D. B. Utton, J. Res. NBS 71A2-442, pp. 125-126 (Mar.-Apr. 1967).

Key words: Measurements at 0 °C; nuclear quadrupole resonance thermometry; potassium chlorate.

It is shown that careful preparation is necessary to achieve a consistent value for the C135 nuclear quadrupole resonance frequency in KCIO, samples at 273.16 °K (the triple point of water). This is illustrated by measurements on a number of samples. It is suggested that the N. Q. R. frequency of C135 in KCIO1 at 273.16 °K and atmospheric pressure is 28,213,372±2Hz. This value is compared with measurements made by previous workers which show a considerable spread. Techniques for the growth of large single crystals of potassium of high purity, H. J. Foster and P. H. E. Meijer, J. Res. NBS 71A2-443, pp. 127-132 (Mar.-Apr. 1967).

Key words: Crystal growth; fermi surface; orientation; potassium; spark cutting; zone refining.

The preparation of large, high purity, single crystals of potassium is described. First, high initial purity is obtained by careful zone refining. Then, a modification of the Bridgman technique is applied which leads to crystals with resistivity ratios up to 6800 at 4.2 °K. The modification consisted of a heat shield as described in the test. We concluded from the magnetoacoustic experiments that were subsequently done with these samples, that the samples had mean free paths of the order of 10-2 cm. Typical crystals were 7/8 in diam and about 8 in long, with growth direction along [110]. A description is given of an easy method of orientation as well as the use of a spark erosion technique to cut and polish the surfaces.

Synthesis of a-L-fucose-1-14 C (6-deoxy-L-galactose-1-14C), H. S. Isbell, H. L. Frush, and N. B. Holt, J. Res. NBS 71A2-444, pp. 133-136 (Mar.-Apr. 1967).

Key words: Carbon-14-labeled L-fucose; L-fuconic acid-/14C; L-fucose-1-14C; radioactive carbohydrates; synthesis of radioactive sugars.

a-L-Fucose-1-14C was synthesized in a radiochemical yield of 30 percent. The synthesis involved degradation of

nonradioactive L-fuconic acid to 5-deoxy-L-lyxose and synthesis from this of a-L-fucose-1-14C by use of 14C-labeled cyanide in the cyanohydrin reaction. The resulting epimeric, 14C-labeled aldonic acids were separated as either the barium or the sodium salts. Both salts of L-fuconic acid crystallize more readily than corresponding salts of the epimeric 6-deoxy-L-talonic acid.

The preparation of barium L-fuconate by the electrolytic oxidation of L-fucose in the presence of barium carbonate and barium bromide is described.

Deuterium isotope effects in a-ß pyranose and in pyranosefuranose interconversions, H. S. Isbell and C. W. R. Wade, J. Res. NBS 71A2-445, pp. 137-148 (Mar.-Apr. 1967).

Key words: Acid-base catalysis in D2O; deuterium isotope effects; D-fructose; D-glucose; isotope effects; mechanism of mutarotation; mutarotation; pyranose-furanose interconversions; sugars in solution.

Rates of mutarotation, catalytic coefficients, and isotope effects are reported for the mutarotations of a-D-xylose, a-Dglucose, and B-D-fructose in H2O and in D2O at 20 °C. The isotope effects (kn/ka) for the mutarotation of B-D-fructose (a pyranose-furanose interconversion) parallel in striking manner the isotope effects for the mutarotation of a-D-glucose (an a-ß pyranose anomerization). For each sugar, the isotope effect is lowest for the acid-catalyzed reaction and highest for the watercatalyzed reaction. The parallelism of the values obtained for the isotope effects under various conditions shows that the ratedetermining steps in the two reactions are similar. Presumably, in both instances, the overall mutarotation arises from concurrent reactions operating on different species of the sugar and showing substantially different isotope effects. The gradual change in the isotope effect indicates that, under the conditions studied, three reactions take place concurrently.

The following isotope effects were found for the mutarotations at 20 °C: For a-D-glucose, kн30+/kp30+=1.39: kн20/kd20=3.87; and kB/k*B-1.83. For B-D-fructose, kн30+/kp20+=1.39; Kн20/KD20=3.87; and kg/k*B=1.92. Mechanisms are presented for the several concurrent acid- and base-catalyzed mutarotation reactions.

Calculated transition strengths between the configurations 5d86s and 5d 6p in Au III, H. Mendlowitz, J. Res. NBS, 71A2-446, pp. 149-156 (Mar.-Apr. 1967).

Key words: Au III; calculated transition strengths; configurations 5d6s and 5d6p.

The transition strengths have been calculated for transitions between configurations 5d6s and 5d6p of Au 111 based upon the wavefunctions given by Shadmi. These strengths have been compared with the estimated intensities given by Iglesias and are found to be in substantial agreement.

Hartree-Fock multiplet strengths for K 1, Ca II, and Sc III, A. W. Weiss, J. Res. NBS, 71A2-447, pp. 157-162 (Mar.-Apr. 1967).

Key words: Multiplet strength; self-consistent field; term values; wavefunctions.

Analytical approximations to Hartree-Fock wavefunctions have been computed for the 4s, 4p, and 3d states of K 1, Ca II, and Sc III. Multiplet strengths for the 4s-4p and 4p-3d transitions in these ions are also computed. Examination of the results indicate that relaxation of the core in the field of the series electron accounts for a large portion of the core polarization effect, at least for the 3d level. Serious cancellation is found to invalidate the dipole velocity results of the 4p-3d transition in Ca

II.