A polarographic study has been made of acetaldehyde, and a method is described for the polarographic determination of acetaldehyde in the complex liquid mixtures and in liquefied C4 distillation fractions obtained in the conversion of ethanol to butadiene. The method is simple, rapid, and accurate, and is superior to the titrimetric methods which are usually used.

The spectra of CC12=CC1CC1==CC12, CC1F=CC1CC1=CC1F, CC1F=CC1CCJ=CF2, CC1F=CFCF=CC1F, CF2=CC1CC1=CF2, and CF2=CFCF=CF2 from 2000 to 2700 Á. were recorded of the gas phase and of hexane solutions. The liquid phase spectra are less well defined but had the general features ascribed to the (Vi *-N) transition of butadiene, with two bands separated by approximately 4000 cm.-1. The higher energy bands were assigned to the (S)-trans configurations. The inductive and conjugative effects of substitution on the energy of the transition may be correlated utilizing Coulson's and Matsen's LCAO-MO calculations. A free electron treatment for substituted butadienes is also presented, and it is shown that the inductive effect may be represented by such a model.

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The "best values" of the parameters in the vaporpressure equations of solid and liquid nickel and the heat of vaporization of nickel are statistically deduced on the basis of all available data. Corrected estimates of the heat of vaporization of NiO(s) and heats of dissociation of NiO(g) and Ni2(g) are obtained. "Best values" of maximum ionization cross sections useful in thermodynamic mass spectrometry are also reported.There have been a number of determinations of the vapor pressures and the heats of vaporization of solid and liquid nickel (3, 9, 76,22,(28)(29)(30)(31)(32)(33)(34)(35)(36)(37). The range of values of these properties was rather large; therefore, a new determination of the heat of vaporization of solid nickel was undertaken, and these results were combined with the available data in the literature to obtain a "best value" of the heat of vaporization and vapor pressures by a statistical treatment. The critical evaluation of the available data was especially desirable since there appeared to be sufficient data in the literature to complete the following thermodynamic cycle, thus lending consistency to the values of the individual heats of reaction.In the process of examining and reducing the data in the literature, new estimates of values of the heats of dissociation of NiO(g) and Ni2(g) were obtained by correcting the available data. Furthermore, during the examination of the mass-spectrometric techniques involved in one of the vapor-pressure determinations, best values of the ionization cross sections of the species H, 0, Ni, Ag, and O2 were deduced. These were then used to correct the available mass-spectrometric data on the pressure of the gaseous species generated by NiO(s) (9). Experimental Methods and ResultsThe method used in determining the vapor pressure of nickel solid was the Langmuir (23) technique. The apparatus used is depicted in Figure 1 and consisted of an RF coil powered by a Sealometic Electronics inductance furnace Model 2000-20 kW operated at a frequency of 3 MHz. The coil, which was used to heat a cylindrical sample to a given temperature, was made of five turns of '/4-in. copper tubing and was 5.75-cm i.d. and 4.5-cm long.The furnace was contained in a bell jar 15.25-cm i.d. X 28-cm high. The specimen was suspended inside the coil by means of 0.0127 c m in diameter tungsten wire, which was looped around the sample to form a harness. The two ends of the wire were hooked to an inconel wire 7.6 cm above the specimen, and the inconel wire, in turn, was hooked to a nylon thread hanging from the end of the electro-balance beam. The enclosure containing the balance and sample was evacuated to l o p 5 torr. 'To whom COrreSDOndenCe should be addressed [Throughout this paper, torr = (101.325/760) kPa; atm = 101.325 kPa; calth = 4.184 J; eV = 96487 J mol-,'; c m -' = 11.927 J mol-'; T = K; A = cm; inch = 2.54 cm; minute = 60 sec; R(calth mol-l K -' ) . I The bell jar which formed the sample chamber was surround-, ed by a water jacket to cool it and to remove condensable gases. The same...

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