摘要:

The azomethane-sensitized pyrolysis of ethane was studied at low temperatures from 280 to 350 °C. Measurements were made of initial rates of formation of methane, nitrogen, and butane. From the rate of nitrogen production the rate constant for the azomethane decomposition into 2CH3 + N2wasA similar study of the propane decomposition, at temperatures from 260 to 300 °C, led to the valuein satisfactory agreement. The rate of decomposition of then-propyl radical into CH3and C2H4was obtained by comparing the rates of formation of C2H4andn-C6H14; the rate constant wasThe activation energy of 31.4 kcal/mole, together with that of 8.9 kcal/mole for the reverse reaction obtained by Brinton, leads to a value of 20.3 kcal/mole for the dissociation energy ofn-CH3—CH CH2at 0 °K, and to a value of 22.8 at 25 °C. The corresponding values for the heats of formation 2of then-propyl radical are 28.4 kcal/mole at 0 °K, and 23.1 kcal/mole at 25 °C. The dissociation energy ofn-CH3CH2CH2—H is deduced to be 99.4 kcal/mole at 0 °K and 99.9 kcal/mole at 25 °C. An energy diagram is constructed for the various reactions ofn-C3H7andi-C3H7.

ISSN:0008-4042    

DOI:10.1139/v66-437

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The kinetics of dehydration and rehydration of lead styphnate monohydrate have been studied as a function of the number of cycles of dehydration and rehydration. The activation energy for dehydration of a repeatedly dehydrated sample is 14.6 kcal/mole compared with 21.7 kcal/mole for the virgin hydrate. Mechanisms for these sorption and desorption phenomena are discussed.

ISSN:0008-4042    

DOI:10.1139/v66-438

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Independent yields for133Xe and135Xe and cumulative yields for133I and135I in fission of233U,235U,238U, and232Th with protons of energies 20–85 MeV were measured. Values ofZp, the most probable charge, were obtained by two different methods. The behavior ofZpfor236U and233U differed considerably from that of238U and232Th. Total chain yields were obtained forA = 133 andA = 13.5.

ISSN:0008-4042    

DOI:10.1139/v66-439

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Propionaldehyde at partial pressures of from 0.0006 to 0.04 mm was photooxidized at 3 100 Å in the presence of 150 mm of oxygen. The major products were ethyl hydroperoxide and carbon monoxide. Acetaldehyde was formed at intermediate concentrations and formaldehyde, ethanol, methanol, hydrogen peroxide, and ethane were minor products. No ozone, peroxy acids, or diacyl peroxides could be detected.The results can be explained on the basis of a free-radical mechanism. Certain radical disproportionation reactions which are often postulated are unimportant because of the low partial pressures of propionaldehyde. An alternative mechanism involving direct chemical reaction of an oxygen molecule with the triplet state of the propionaldehyde may be of some significance, but cannot account for all of the products obtained. The present results indicate the importance of alkyl hydroperoxides as products in photooxidations at low partial pressures of aldehyde in the presence of large excesses of oxygen.

ISSN:0008-4042    

DOI:10.1139/v66-440

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

After a brief summary of recent advances in the structure of the positive column of a d-c. glow discharge, general expressions are derived for rates of reaction and excitation produced by electron impact. These rate equations are expressed in terms of the easily measured electrical parameters of the discharge. Such expressions will be used in future studies of chemical reactions occurring in the positive column; a qualitative comparison to experiment is given, where possible.A general expression for the axial electric field in the positive column is obtained by equating the energy gained by the electrons in this field to that lost by collisions. The main assumption made is that axial electron concentration be constant along the column.In the second part of the paper, calculations are done which indicate that ion and electron concentration gradients exist in the positive column adjacent to the anode. It is pointed out that such a phenomenon will be pronounced only under special conditions of low transverse and high axial field, and will be enhanced with fast-flowing gases.A sample calculation is presented using the expression for the rate of electronic excitation of a species by electron impact, assuming a Maxwell–Boltzmann energy distribution for the electrons and constant elastic and inelastic collision cross sections.

ISSN:0008-4042    

DOI:10.1139/v66-441

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Discharges through fast-flowing oxygen have been investigated. It has been shown that the electrical field remains constant in the positive column of a particular mode, even in the presence of a large pressure gradient. It was found that five types of discharges could be distinguished and they can be characterized by fluctuations of the voltage at the electrodes. These oscillations are linked with the absence or presence of travelling waves in the column. The conditions of existence of the various discharges are outlined. It has also been shown that the structure of the positive column is not as homogeneous as previously thought. In particular, even at constant field, changes in the electron temperature and the number density of charged species are shown to occur. The change in electron temperature and the presence or absence of oscillations have been shown to affect the rate of production of atomic oxygen and the emission intensity of the spectrum of these discharges.

ISSN:0008-4042    

DOI:10.1139/v66-442

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Infrared spectra of H2O and D2O in benzene have been recorded and the solubilities of light and heavy water in benzene from 10 to 50 °C measured. Isotope fractionation factors for the distribution of HDO and H2O between the vapor and liquid benzene phases were calculated from the relative solubilities and the vapor pressure ratios of pure H2O and D2O. The isotope equilibrium data was fitted to the expression ln α = −A/T2 + B/Tand interpreted by the Bigeleisen formulism. The intramolecularBterm was determined from the solvent shifts of the near infrared frequencies and the intermolecularAterm calculated by a least squares fit to the isotope equilibrium data. Spectral and equilibrium data were combined to give.

ISSN:0008-4042    

DOI:10.1139/v66-443

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The diarsenides of the cobalt and nickel families have been synthesized for magnetic susceptibility studies. The diffraction pattern of the low-temperature modification of nickel diarsenide differs from that of the mineral pararammelsbergite, although the space group is apparently identical and the unit cell dimensions comparable (orthorhombica = 5.770 ± 0.007,b = 5.838 ± 0.006,c = 11.419 ± 0.008 Å). These binary diarsenides exhibit temperature dependent diamagnetic or weakly paramagnetic behavior. Temperature dependence of electrical resistivity indicates that PdAs2is metallic while PtAs2is a semiconductor with an energy gap of ~0.17 eV.Substitutional solid solution limits have been determined for various Group VIII transition metal atoms in the pyrite phases PdAs2and PtAs2, and in the skutterudites RhAs3and IrAs3. There is no substitution by Ru or Os in PdAs2, by Ni or Pt in PdAsa, by Ru or Ag in RhAs3, or by Os in IrAs3. Very limited substitutions were observed for Rh and Ag in PdAs2, Pd in PtAs2, Pd in RhAs3, and Pt in IrAs3. The limit of Co substitution in PdAs2is 8.2 ± 0.3 atom %, and of Ni in PdAs2, 56.7 ± 0.3 atom%.In the CoxPd1−xAs2system, a temperature-dependent paramagnetic contribution corresponding to approximately one uncompensated spin per cobalt ion has been attributed to thet52glow-spin configuration of the Co ion in the pyrite structure. In the NixPd1−xAs2system, the temperature-independent paramagnetic contribution by the nickel ions is not completely understood.

ISSN:0008-4042    

DOI:10.1139/v66-444

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

A comparison has been made of seven numerical methods of fitting infrared absorption band envelopes with analytical functions using nonlinear least squares approximations. Gauss and Cauchy (Lorentz) band shape functions are used, and also sum and product combinations of the two. The methods have been compared with respect to both the degree of convergence and to the computation time needed to achieve an acceptable fit.The most effective method has matched the overlap envelope of a steroid spectrum containing 16 bands; this necessitated the optimization of 65 variables. More complex spectra can be dealt with by a "moving subspace" modification in which only the parameters of a group of adjacent bands are adjusted at one time. Automatic computer programs have been written for five of the methods, and for the moving subspace modification. These will be published elsewhere.If the computed curve is convoluted with the spectral slit function before making the least squares calculations, the distortion of the observed spectrum caused by the finite spectral slit width can be corrected. In some cases this method of diminishing the slit distortion is better than direct methods, particularly when dealing with strongly overlapped bands.

ISSN:0008-4042    

DOI:10.1139/v66-445

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The spectral behavior ofo- andp-nitroanaline adsorbed on various alkaline earth compounds has been studied by reflectance spectroscopy. Regular bathochromic shifts in the diffuse reflectance spectra have been observed for the absorption maxima in the visible region in order of increasing size of the adsorbent cation. Progressive removal of coadsorbed moisture which competes for active adsorbent sites resulted in an enhancement of the bathochromic shifts. The intensity of the absorption maxima as measured by peak heights was found to be dependent upon the size of both cations and anions of the adsorbents. Interpretation of observed phenomena was advanced in terms of electronic polarization theory and varying surface area of the adsorbents.

ISSN:0008-4042    

DOI:10.1139/v66-446

出版商:NRC Research Press    

年代:1966

数据来源: NRC