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C 14 produced by the N u (n, p) reaction of cosmic-ray neutrons has been detected and identified. The C 14 concentration of biological methane was enriched by factors of up to 260-fold by thermal diffusion to raise the activity to convenient levels for counting. The pure methane was used as the filling gas in large Geiger-Mtiller counters.The activity in biological methane was found to be 10.5 disintegrations per minute per gram C, or 0.95 X10~1 2 gram C 14 per gram C. This is in reasonable agreement with the value predicted from the estimated values of the cosmic-ray neutron flux and the amount of carbon in exchange equilibrium with the atmosphere. No significant activity was detected in petroleum methane.A discussion of the thermal diffusion enrichment factor is given.

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36 These figures include in addition to the organoaluminum compounds, any combinations which can be made from inorganic substituents. 4 In the text, "Die Chemie der metall-organischen Verbindungen" by E. Krause and one of the authors, the term "alphyl" is used to denote the aliphatic radicals, and "alkyl" in a broader sense to include both aliphatic and aromatic groups. Conforming to common usage in this country, the term alkyl as used in the present paper refers only to aliphatic radicals. 106 SUMMARY 1. Organoaluminum compounds have been prepared by the reaction of aluminum metal with a series of alkyl halides. These halides are methyl and ethyl chlorides, bromides and iodides, and n-propyl iodide.2. By diverse methods each of the dialkylaluminum halides and alkylaluminum dihalides corresponding to the above alkyl halides has been obtained in pure form.3. The preparation of phenylaluminum dichloride, dibromide, diiodide and p-tolylaluminum diiodide is described.4. Alkylaluminum alkoxides have been prepared by the reaction of aluminum alkyls with aluminum alkoxides.5. Dialkylaluminum halides have been prepared directly by the reaction of alkyl halides with an aluminum-magnesium alloy.6. A new method for preparing aluminum alkyls involving the reaction of alkylaluminum halides with alkali metals is described. Riverside, III.