The relative fluorescence output and Eu3+ level lifetime, T , of crystalline Eu(hfaa)4ButNH3(hfaa = hexafluoroacetylacetonate anion) have been measured over the temperature range 90-300 K.

An apparatus has been designed for the measurement of very low gas solubilities (ca. 1 0-6 mol fraction), allowing fast equilibration between the solute and solvent. The solubilities of NF, (298-31 8 K) and of N2F4 (288-31 8 K) in water have been determined, and the enthalpies and entropies of solution derived.GAS solubilities are relevant to the theoretical understanding of the liquid state and solutions, and to such practical applications as understanding the mechanism of the toxicology of inhaled gases. The anomalous solubility properties of fluorine compounds have proved to be of great importance in the thermodynamic study of aqueous 293 and non-aqueous 4-6 solutions. Ashton ef aL3 have constructed an apparatus specifically designed to measure gas solubilities of the order of mol fraction and they report the solubilities of CF,, SF,, and NF, in water between 275 and 323 K.The aqueous solubilities of NF, and N2F4 are important in the understanding of their toxicity. Toxicological and other studies '-11 have shown that inhalation results in methaemoglobin formation, though it is less certain how far this is a primary lethal factor. Kinetic experiments l1 have demonstrated the considerable oxidative capacity of these gases although in pure water NF, has been shown to be inert even at 406 K. N,F,, after long induction periods (several days at 333 K), undergoes hydrolysis9with an exponential increase in reaction rate. However, exposure to a mixture of 1% (v/v) of NF, in air for 70 min, or to the same concentration of N2F4 for 25 min, was almost invariably lethal to rats.8J0 Since the first stage of intoxication presumably is the dissolution of the gas, the aqueous solubility is clearly important.An apparatus was designed for the measurement of t mmHg = (101-325/760) kPa.

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The ionization potentials of P2F4, PF3, PFIH and PFJ and the appearance potentials of the PF; ion from these species are reported. The ionization potential of the PFy radical is estimated using approximations for the PF2-X (X = F, I and H) bond dissociation energies. The P-P bond dissociation energy in diphosphorus tetrafluoride is estimated as 57-t 10 kcal mol-'.$ EXPERIMENTAL MATERIALS PFzI was prepared as previously described. PF3, formed as a by-product in the preparation of PF21, was separated from the latter by high-vacuum trap-to-trap distillation through traps held at 11 3 K. PF21 was retained at 113 K and PF3 at 77 K ; no further purification of the PF3 was required.

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