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Dans le but d’expliquer les resultats assez contradictoires obtenus anterieurement, nous avons effectue un ensemble d’experiences sur l’effet thermique des compteurs de Geiger-Muller entre 20 ‡C et 250 ‡C, en utilisant divers remplissages autocoupeurs et des detecteurs a cathode interne ou a parois de verre et graphitage externe. Le coefficient de temperature, proportionnel a la pression partielle du constituant polyatomique, est du a sa desorption reguliere depuis les parois. La caracteristique de palier s’ameliore lorsque la temperature augmente, et l’effet nefaste d’ions negatifs possibles, produits par la vapeur de mercure existant en tres faibles proportions dans le remplissage, est nul, contrairement a certaines hypotheses anterieures. La deterioration progressive de la caracteristique au dessus d’une certaine temperature est due a un phenomene etranger a la decharge, reversible (degagement de vapeur d’eau depuis les parois, augmentation du mouvement propre) ou irreversible (decomposition de la vapeur polyatomique ou reaction chimique sur les parois). Les compteurs a parois de verre non etuves manifestent une stabilite remarquable: jusqu’a 250 ‡C ne se produit aucune augmentation sensible du fond, et, jusqu’a une temperature t0 voisine de 100 ‡C, leur coefficient thermique est tres inferieur a celui des compteurs a cathode interne du type classique. Au dessus de t0, la variation est plus rapide.

The nitrogen isotopic discrimination of some salts and metals, studied in liquid ammonia solution at -50oC, decreases in magnitude in the order Pb{sup++}, Ca{sup++}, Li{sup+}, Ag{sup+}, Na{sup+}, Li, K{sup+}, Na, K. The isotopic discrimination appears to provide qualitative information about the strength of the cation-solvent interaction in liquid amonia.

To establish whether tektites are extraterrestrial in origin, five composites including a total of 79 tektites from the Far East and Australia were examined for cosmic-ray-induced Al26 by γ-γ coincidence spectrometry. No activity was found in any of these samples, corresponding to 2σ upper limits for the Al26 content of ≤1.6 to ≤8 dpm/kg, or about ≤3 to ≤13 per cent of Al26 content of meteorites. A grand composite of all the above samples showed a marginal positron activity corresponding to an Al26 content of 0.48±0.26 dpm/kg, but this activity can apparently be accounted for by reactions of cosmic-ray secondaries at the surface of the earth with silicon and aluminum in the tektites. No evidence was found for a preterrestrial exposure to cosmic rays. These results do not completely rule out an extraterrestrial origin but do place the following restrictions on it: if the tektites arrive as small, unshielded bodies, their ‘flight’ or cosmic-ray exposure time was less than 90,000 years; if they arrived in a large, well-shielded body, this ‘prototektite’ body must have had a radius of ≤54 meters.

Average Energy of Configuration. Valence Orbital Ionization Potentials (VOIPs) are reported for the elements H through Kr in various configurations and for many states of ionization. For the lighter elements the isoelectronic series are fitted to a quadratic equation, VOIP (q)=Aq 2 + Bq+C. The significance of the A, B, and C parameters is discussed.

Self-consistent charge and configuration (SCCC) molecular orbital calculations are reported for 32 selected octahedral and tetrahedral first-row transition-metal complexes containing halide and chalcogenide ligands. It is found that for the range of metal oxidation states II through IV, Fsigma, chosen to fit the experimental Delta, is a function of only the metal atomic number for constant Fpi. In the range of formal metal oxidation numbers V through VII, Fsigma is also a function of oxidation number.Calculated and observed trends in covalency, Delta values, and first L-->M charge-transfer energies are compared. The conclusion is drawn that the molecular orbital method, in its present formulation, gives a reasonable account of the ground states and low excited states in simple metal complexes.

N -(1,1-Dimethylpropynyl)-3,5-dichlorobenzamide is representative of a group of benzamides that are herbicidally active on annnual and perennial grasses with potential agricultural uitility in forage legumes, certain turf grasses, and clultivated crops.

A new synthetic group of pyridones represented by 3-carboxy-1-(p-chlorophenyl)-4,6-dimethyl- 2-pyridone are growth regulators in various agronomic and ornamental plants.