摘要:

Contact angles are reported for aqueous solutions of valeric acid on copper, stainless steel and polytetrafluoroethylene surfaces in equilibrium with their own vapors at atmospheric pressure and 25 °C. It is demonstrated that the dependency on concentration for the polytetrafluoroethylene surface is in accord with theory.

ISSN:0008-4042    

DOI:10.1139/v72-258

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The relative increase in the free ion yield with increasing field strengthE, expressed asis smaller when the following quantities are larger: (1) dielectric constant, (2) temperature, and(3) separation distance between the geminate ion–electron pairs. The field dependenceequals 9.7/ϵT2 cm/V at lowE, but at higher fields it is affected by the above three factors and byEitself. Results obtained from the liquids propane (123–233 °K), 2-methylpropane (isobutane, 148–294 °K), 2,2-dimethylpropane (neopentane, 295 °K), argon (87 °K), oxygen (87 °K) and argon–oxygen solutions (87 °K) are presented and analyzed according to a theoretical model. Several types of ion–electron separation (y) distribution functions are tested. Within the framework of the model a power function F(> y) = yminy−xwithx < 4 provides a good interpretation of the results whena Gaussian distribution function provides the best interpretation of the field effects whenEither theydistribution has a Gaussian core with a more gently sloping tail, or distributions are more Gaussian-like in liquids in which the electron ranges are greater. The electron range in pure argon (b = 1300 Å) is much smaller than had been expected and is only 2.6 times greater than that in liquid methane (b = 500 Å at 120 °K). Phonon emission by 10–0.01 eV electrons in liquid argon may be relatively efficient and might involve transient states of the type

ISSN:0008-4042    

DOI:10.1139/v72-259

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Heats of solution and heats of dilution of lithium chlorate in water and dioxane–water mixtures have been determined experimentally. From these data apparent molal heat content, ΦL, and relative partial molal heat contents of solvent,and of solutehave been calculated. The values of ΔG0, ΔH0, and ΔS0are also calculated.

ISSN:0008-4042    

DOI:10.1139/v72-260

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

This paper shows that it is possible to convert a protected peptide containing djenkolic acid to the corresponding peptide containing cystine. Thus, the tripeptide8and the pentapeptide9were converted to peptides10and11respectively by treatment with bromine in anhydrous medium followed by an hydrolysis. The pentapeptides9and11were then deprotected and purified by filtration through Sephadex G-10 to give respectively the pentapeptide bis-γ-L-glutamyl-L-djenkolyl-bis-glycine (7) and oxidized glutathione (2) with overall respective yields of 57 and 38% from djenkolic acid (1).

ISSN:0008-4042    

DOI:10.1139/v72-261

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The alkaloids ofOrmosiasemicastratahave been shown to be (−)-ormosanine, (±)-piptanthine, (−)-18-epiormosanine, and (−)-ormocastrine. The structure and relative configuration shown in1have been assigned to ormocastrine on the basis of its 220 MHz n.m.r. spectrum and its conversion to ormosanine, among other products, on hydrogenation.

ISSN:0008-4042    

DOI:10.1139/v72-262

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The adsorption of Co(II) by Fe3O4, Al2O3, and MnO2has been studied as a function of Co(II) concentration, solution-pH, and temperature. It is observed that the adsorption of cobalt increases markedly with the solution pHbetween pH5 and 7.5. Above pH8 adsorption becomes increasingly masked by precipitation of Co(OH)2and no resolution of these two contributions to the loss of Co(II) from solution is possible. A log θ/(1–θ) vs. pHplot is found to be linear between pH5 and 7.5, where θ is the fraction of occupied adsorption sites. The presence of 0.1 mBa2+and Mg2+in the solution does not seem to affect the hydrogen ion dependence of the adsorption of Co(II) on alumina.The adsorption results have been analyzed by the Langmuir adsorption isotherm over a wide range of Co(II) concentration (10−6–10−3 m). The adsorption of Co(II) is found to be an endothermic process and increases markedly with temperature between 30 and 100 °C. The heat of adsorption decreases with increasing surface coverage of the oxides. At saturation coverage, the heats of adsorption for Co(II) on Al2O3, MnO2, and Fe3O4are −14.9, −14.3, and −6.3 kcal/mol, respectively. Hydrolysis of Co(II) is suggested as a possible mechanism for the marked dependence of adsorption on pHand temperature.

ISSN:0008-4042    

DOI:10.1139/v72-263

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Improved values for two acidity constants of 2,3-dihydroxypyridine have been computed using program PITMAP. The composition of the complex with iron(III) and its conditional and overall stability constants in 1 Mhydrochloric acid have been evaluated.

ISSN:0008-4042    

DOI:10.1139/v72-264

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Wyss and Falk's infrared absorptivities between 10 and 85 °C for HDO in liquid D2O in the fundamental O—H stretch region have been analyzed numerically and show a statistically significant weak band near 3600 cm−1at each temperature. This band, the Raman analog of which was reported earlier, confirms the presence of HDO species with unbonded O—H groups in the liquid state. The percentage of HDO species with un-bonded O—H groups is found to be 4.6, 6.1, 10.1, and 11.9, respectively, at 10, 35, 60, and 85 °C.The four predominant HDO species in equilibrium at low temperatures are denned together with their equilibrium constant for thebond-rupturing process. A standard enthalpy change of ΔH° = 6800 ± 1100 cal is found for the rupture of one mole ofbonds. This is in contrast with the apparent enthalpy change of 2900 ± 500 cal, as usually derived from the temperature dependence of the equilibrium quotient. Approximate mole fractions for each of twelve differently bonded HDO species are derived from a model for random H- and D-bond statistics. Results show that the four predominant HDO species give a full interpretation of the absorptivities at 10, 35, and 60 °C but that additional minor species contribute slightly to the absorptivity at 85 °C.

ISSN:0008-4042    

DOI:10.1139/v72-265

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The adsorption of monomethylamine has been studied near its boiling point, 266 °K, on silica–alumina and on a wide range of silica gels by measurement of adsorption–desorption isotherms and isothermal calorimetric heats of adsorption. In addition, surface areas and pore-size distributions have been determined by low-temperature nitrogen adsorption. Heats of adsorption on Davison "923" silica gel varied from around 33.0 kcal/mol at θ = 0.01 to 6.2 kcal/mol at monolayer completion. Maxima were observed in this heat curve in the regions of θ = 0.15, 0.28, and 0.40. These phenomena are believed to be related to interactions among the adsorbed species in pores of diameters approaching molecular dimensions. Heats of adsorption on silica–alumina fell smoothly from 39.5 kcal/mol at θ = 0.03 to 13.0 kcal/mol at θ = 1.00. Adsorption–desorption characteristics of methylamine were also examined on a series of silica gels with widely different pore structures. The variations in the heats of adsorption with surface coverage are discussed in terms of both the nature of the adsorbed surface species and lateral interactions among the adsorbed molecules.

ISSN:0008-4042    

DOI:10.1139/v72-266

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Catechol reacts with boron sulfide to give 2,2′-o-phenylenedioxybis-(1,3,2-benzodioxaborole) (1) while only the hydroxyl function of salicylic acid reacts to give a quantitative yield of tris(o-carboxylphenoxy)borane (3). Phthalic acid is dehydrated to phthalic anhydride, but succinic acid and maleic acid have been found inert to the action of the boron sulfide.

ISSN:0008-4042    

DOI:10.1139/v72-267

出版商:NRC Research Press    

年代:1972

数据来源: NRC