All isomers, except 3-and 5-cyclohexyleicosane, have the strongest maximum in the 9.0-9.5 µ bands at approximately 9.29 µ. The maximum is at 9.245 µ for 3-cyclohexyleicosane and at 9.23 µ for 5-cyclohexyleicosane. The latter isomer is the only one to have a band at 11.60 µ. 7-Cyclohexyleicosane is the only member of the series which has an absorption maximum at 12.73 µ, although a few of the isomers have broad shoulders near this wave length. 9-Cyclohexyleicosane has a sharp maximum at 8.96 µ which is equal in intensity to the 8.88 µ band. Moreover, this isomer has a broad shoulder at about 11.42 µ, which is also conspicuous in 9-cyclohexylheptadecane. CONCLUDING REMARKSIt has not been an object of the present work to determine the purity of the compounds investigated. To do so would have required a detailed consideration of the method by which each compound was synthesized and of the impurities likely to occur in it, as well as observation of the absorption spectrum of each compound at different stages of purification. Although the results obtained in comparing the various spectra with one another and with the spectra of related compounds indicate that the purity is high, it would not be surprising if one or more of the weaker absorption maxima observed should be found to have been caused by impurities. Nevertheless, the spectra presented here should be adequate for estimating the possibilities and limita-tions of the application of infrared spectroscopy to the identification of phenyl-and cyclohexyleicosanes and to the analysis of mixtures containing these compounds. ACKNOWLEDGMENTSThe writers wish to acknowledge their indebtedness to the American Petroleum Institute, and to the late F. C. Whitmore and R. W. Schiessler of Pennsylvania State College, for the loan of the hydrocarbons. One of the authors (K. S.) wishes to express her gratitude to the Ethyl Corporation for the grant of a fellowship. LITERATURE CITED

Qualitative infrared spectra in the solid phase of crystalline sodium penicillins G, F, X, K, and amyl are presented as a basis for quantitative analysis. Suitable analytical infrared absorption frequencies are listed. The details of an analysis in the solid phase, with an accuracy of ± 2.0 %, for crystalline sodium penicillin G are given. Spectroscopic SHORTLY after Fleming's discovery of penicillin it was evident that because of its instability and other chemical properties the purification, isolation, characterization, and analysis of the antibiotic would not be an easy task. As purification of the material progressed it was soon found that a multiplicity of types of penicillin was produced by the mold, each type possessing its own specific antibiotic activity and properties. Because of these

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