Thermochromatography / Gas-solid chromatography I Chromatographie Zone Profites /Monte Carlo simulations fEnthalpy of adsorptionSummaiy A simplifled microscopic model is proposed for the gas-solid thermochromatography in open columns with the laminar flow of the carrier gas. This model describes the downstream migration of a sample molecule as a rather small number of some effective random displacements, and sequences of adsorptiondesorption events that occur without changing the coordinates. The relevant probability density distributions are thereby derived, Based on this model, a versatile Computer program has been developed for simulating the profiles of thermochromatographic zones by employing the Monte Carlo technique. Some results of these simulations are given to demonstrate the influence of several parameters on the zone profile.

By the experimental measurement of deposition temperatures as a function of time and/or the gas flow rate in a column with constant negative longitudinal temperature gradient one can evaluate the differential molar standard enthalpies and entropies of adsorption by the second law method. On the basis of model conceptions with respect to the adsorbed state the differential molar standard adsorption entropy can be estimated. This allows the enthalpy of adsorption to be evaluated only from the deposition temperature by a quasi-third law method. Pertinent formulae are deduced.

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Element 105 / Transition metal group V / Chemical properties / Bromides / Volatility / Gas chromatography AbstractThe retention behavior of volatile bromide molecules of shortlived isotopes of tantalum and element 105 in KCl coated quartz columns was studied using continuous isothermal gas chromatography. HBr and HBr saturated with BBrs vapor were used as reactive gases. The isotopes were produced in the fusion reactions ^°Ne+"" Eu and ^^O + ^^^Bk, respectively. The reaction producta were transported from the accelerator to the chromatography set-up with a gas-jet system using an aerosol with He as carrier gas and KCl as transporting particles. The measured retention times are compared to those of "'Nb bromides from a previous study. The retention times of niobium and tantalum bromides are very similar, in agreement with expectations based on the nearly identical Sublimation enthalpies of NbBrj and TaBr;. For the bromides of element 105, higher retention times are found, indicating a lower volatility of lOSBrs than of NbBrs and TaBrs. On the basis of empirical systematics, a Sublimation enthalpy of 138± 15 kJ/mol can be estimated for 105Br5 from the experimental data.

SummaryWe present results of the second experiment on the chemical identification of element 112. Similar to the first test in 2000, we aimed at the production of the spontaneously fissioning

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