摘要:

Calorimetric heats of adsorption have been determined for sulfur dioxide adsorbed at 298, 323, 373, and 423 K on both Californian and Quebec chrysotiles. Adsorption isotherms have been measured and some differential molar entropies calculated. Thermal desorption of surface species resulting from the adsorption of sulfur dioxide on Californian chrysotile at 298 K have been studied from 25 to 450 °C. Sulfurous and carbonic acids, in addition to sulfites and other trace species, have been shown to result from the adsorbent–adsorbate interactions. A mechanism for sulfur dioxide adsorption on chrysotile has been prepared which accounts for the observed high heats of adsorption measured at low surface coverages.

ISSN:0008-4042    

DOI:10.1139/v78-300

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Vapour pressures of concentrated solutions (up toI = 14) of the Systems CaCl2 + NaCl + H2O and MgCl2 + NaCl + H2O have been measured at 25 °C by the static method. By means of reverse application of the Reilly–Wood–Robinson and Zdanovskii–Stokes–Robinson equations to these data, water activities of supersaturated NaCl solutions up to ∼15 mhave been deduced, and are represented in polynomial form.

ISSN:0008-4042    

DOI:10.1139/v78-301

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The optical spectra of the charged ions obtained from γ-irradiation of dilute alkyl mercaptans, sulfides, and disulfides in a variety of dilute rigid glasses are measured at 77 K. The photochemical stability of these ions is determined. A new photochromic species has been found. It is derived from a mercaptan dimer cation and is analogous to the photochromic anion produced from alkyl disulfides. The results of γ-radiation are compared to the uv photolysis of similar matrices, and it is found that the thiyl (RS•) and perthiyl radicals (RS2•) are not generally in evidence in γ-irradiated matrices although they may be obtained by appropriate annealing or photobleaching of the irradiated matrix. The ions which have been characterized optically are RSH+, RSH−, RSSR+or their dimers, and RSS(H)R. The relative stabilities of these species in the low temperature glasses are determined.

ISSN:0008-4042    

DOI:10.1139/v78-302

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

We studied the photolysis of isoprene at wavelengths between the absorption threshold (ca. 255 nm) and 147.0 nm. The pressure effect was studied between 30 and 2660 N m−2. At the lower energy, light products are formed and their yields decrease with an increase in the pressure. From Stern–Volmer plots, we have concluded that the photoexcited molecule is collision stabilized at high pressure. Less pressure dependence was observed at 174 and at 163.3 nm. At these energies, and at 147 nm, all of the photoexcited molecules decompose. At 147 nm, no pressure effect was observed, and the main product is vinylacetylene (Ф = 0.66). The formation of this product was explained on the basis of the CH3—C4H5split followed by the fragmentation of the excited C4H5* radicals. At 174 nm, this last radical is collisionally stabilized. Finally we have measured the ratiok(CH3 + H2S)/k(CH3 + isoprene) = k1/k12andk1/k12 = 41 + 

ISSN:0008-4042    

DOI:10.1139/v78-303

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

We have made beat capacity and density measurements leading to apparent molar beat capacities and volumes for dilute aqueous solutions of Na2SO4, K2SO4, Na2S2O3, Na2S2O8, K2S2O8, K2CrO4, Na2MoO4, and Na2WO4. We have used these apparent molar quantifies to extrapolate to infinite dilution to obtain the corresponding standard state apparent and partial molar quantities. These latter values have been used in calculation of conventional ionic beat capacities and volumes.

ISSN:0008-4042    

DOI:10.1139/v78-304

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The oxypentafluorouranates(VI) MUOF5, where M = NH4, K, Rb, Cs, have been synthetized from reaction of UOF4with the ammonium or corresponding alkali metal fluoride in liquid SO2. According to X-ray diffraction, Raman and infrared spectroscopy, and from an isomorphism with the corresponding hexafluorouranates(V) MUF6, two different environments around the uranium atom are observed. In CsUOF5the five fluorine atoms and the oxygen around the uranium result in a pseudo-octahedral surrounding whereas for the other complexes (M = NH4, K, Rb) each uranium is surrounded by eight light atoms forming a dodecahedron. In this structure the dodecahedra are linked together by fluorine atoms to form infinite chains. The UOF5−ion has been characterized by vibrational spectroscopy in the solid state. The proposed assignment, which was made with the assumption of a C4vsymmetry of the UOF5−ion, was confirmed by a force constant calculation. From these data and contrary to the values reported for comparable oxypentafluoroanions, the axial fluorine is found to be less ionic than the equatorial ones.

ISSN:0008-4042    

DOI:10.1139/v78-305

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Ultrasonic absorption measurements are reported for the System HCl–dimethylsulfoxide (DMSO)–water in the frequency range 3.5 to 140 MHz. For ail solutions studied, the excess absorption due to the presence of HCl can be fitted well with a single relaxation equation. For 0.10 molℓ−1solutions of HCl in DMSO–water mixtures, no further relaxations at higher frequencies are likely. Reasonable results are obtained when the ultrasonic results are analyzed assuming the process responsible for the excess absorption to be the dissociation–association equilibrium of HCl, and using equilibrium constants determined from conductivity (C. Cookeetal. Electrochim. Acta,20, 591 (1975)). The value of |ΔVeff| is 20–25 cm3mol−1andKassis approximately 3 × 109ℓ mol−1s−1, as compared to a value of 10 × 109ℓ mol−1s−1calculated from limiting conductivities assuming diffusion-controlled rate t

ISSN:0008-4042    

DOI:10.1139/v78-306

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The yields and reactions of trapped electrons which absorb in the visible (evis−) and infrared (eir−) have been studied by pulse radiolysis in deuterated aqueous 6–15 MLiCl glasses at low temperatures. At 76 K G(evis−) increases and G(eir−) decreases as the concentration of LiCl is increased, butover the whole concentration range. Because the hydration number of Li+is 4,G(eir−)/G(evis−) was plotted against [free D2O]/[LiCl•4D2O] and found to give a straight line passing through the origin, for [D2O]/[LiCl] > 4. From this proportionality it is concluded that eir−is an electron trapped in a purely amorphous water environment and evis−is mainly associated with water bound to Li+.The reactions of eir−and evis−with Cu(II) and SeO42−have been investigated. At 138 K the rate of reaction of evis−with SeO42−increases with decreasing [LiCl] whereas its rate of reaction with Cu(Il) is slower and independent of [LiCl]. At 76 K, where the rates of reaction of eir−with the scavengers can also be measured, it is found that in each case evis−and eir−react more slowly in 12 MLiCl glass than in 6 MLiCl glass, the difference being more marked for SeO42−. In the absence of scavenger the electron in the smaller yield decays faster. These observations can be rationalized on the basis that electrons can tunnel in either direction between visible and infrared traps before being scavenged, and it seems they cannot be rationalized in terms of direct tunnelling only.G(Cl2−) is found to be proportional to the electron fraction of Cl−•3D2O in the glass and its extrapolated value for pure Cl−•3D2O is 3.4. It is inferred that Cl2−arises mainly from ionization of the D2O bound to Cl−.

ISSN:0008-4042    

DOI:10.1139/v78-307

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

13C nuclear magnetic resonance spectra of diastereomeric C-24 alkyl sterols have been assigned. Differences in the chemical shifts of side-chain carbons permitted the determination of the absolute configuration at C-24 in several sterols since these chemical shifts are insensitive to structural changes remote from the asymmetric centre. An unknown sterol fromTetraselmissuecicahas been identified as (24R)-24-methylcholest-5-en-3β-ol and the configuration assigned from1H nmr data to the sterol fromPhaeodoctylumtricornutumhas been confirmed. The utility and potential of this method in characterising new sterols and their biological precursors is discussed.

ISSN:0008-4042    

DOI:10.1139/v78-308

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Synthetic (±)-flavipucine (C12H15O4N) is monoclinic, space groupP21/c, witha = 11.506(5),b = 8.765(5),c = 11.981(7) Å, β = 91.09(2)°,Z = 4. X-ray analysis confirms its structure as1, 3′-isovaleryl-6-methyl pyridine-3-spiro-2′-oxiran-2(1H),4(3H)-dione and reveals the configuration of the oxirane to beZ.

ISSN:0008-4042    

DOI:10.1139/v78-309

出版商:NRC Research Press    

年代:1978

数据来源: NRC