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At high chloride concentrations (2 mol dm–3) the oxidation of chloride to chlorine by Ce4+ ions, i.e. 2Ce4++ 2Cl–→ 2Ce3++ Cl2 was found to be catalysed by an activated form of ruthenium dioxide hydrate (RuO2·x′H2O*). A kinetic study of this process revealed that the disappearance of Ce4+ ions was first-order with respect to the concentrations of Ce4+ and redox catalyst, and zero-order with respect to the concentrations of chloride and Ce3+ ions. On reducing the chloride concentrations below a threshold value, ca. 0.2 mol dm–3, the Cl2 and O2 yields were found to decrease (from 98 to 0%) and increase (from 0 to 95%), respectively, although the rate of disappearance of the Ce4+ ions remained almost unaffected. At [Cl–] < 0.01 mol dm–3 only O2 evolution was observed. These results were interpreted using an electrochemical model in which the catalyst particles were assumed to be acting as microelectrodes and the current density due to chlorine evolution was proportional to the square of the chloride concentration. In addition to activated ruthenium dioxide hydrate several other materials were tested successfully for catalytic activity, including non-activated ruthenium dioxide hydrate (RuO2·xH2O). However, unlike RuO2·x′H2O* these other materials did not catalyse the oxidation of water to oxygen by Ce4+ ions in the absence of brine.

SUMMARY (2) All four species home to an artificial shelter placed in their culture bins. Use of the home and closeness of aggregation in it may be described by the series L. pseudoflavus = L. flavus > L. maximus > L. marginatus, in which, L. pseudoflavus and L. flavus form closed packed huddles, L. maximus ceases movement on making contact with another slug, and L. marginatus adopts a spaced distribution, in single species groups. (3) Once within the home, L. maximus, L. pseudoflavus and L. flavus do not change their behaviour in mixed species groups. The distribution of L. marginatus, however, is disrupted by the close approach of members of other species. (4) When mixed with L. pseudoflavus or L.flavus, significantly more L. marginatus and significantly fewer L. maximus occupy the home; L. flavus and L. pseudoflavus have nearest neighbours of the same species significantly more often than chance would

A simple, inexpensive method has been devised for the analysis of chlorine-oxygen gas mixtures using a flow system, i.e., a system in which the gas sample under test is injected into a mixing chamber and swept out by an inert carrier gas (N2) to a chlorine trap and then an oxygen detector. Any chlorine gas (down to ca. 10 µl) present in the injected sample was found to be reduced quantitatively by the iodide present in the trap solution placed directly after the mixing chamber. The amount of triiodide formed as a result of this reaction was then determined spectrophotometrically. Removal of the chlorine by the iodide trap allowed any oxygen (down to ca. 20 µl) present in the sample then to be detected using an oxygen membrane polarographic detector (O2-MPD). In addition, a chemical system for the in situ generation of accurately known amounts of chlorine gas was developed and the wide range over which it can be applied (10 ml-10 µl) was demonstrated using the flow system. In the chemical system, accurately known amounts of CeIV ions were injected into a strong brine solution (2 mol l–1) to which a small amount of thermally activated RuO2.xH2O had been added. The thermally activated RuO2.xH2O acted as a redox catalyst for the quantitative reduction of the injected CeIV ions by the chloride ions via the reaction 2Ce4++ 2Cl–→ 2Ce3++ Cl2. Interestingly, in the absence of brine, this chemical system will generate oxygen via the quantitative reduction of the injected CeIV ions by water, i.e., 4Ce4++ 2H2O → 4Ce3++ 4H++ O2. As a result, it can also be used to generate accurately known amounts of oxygen and chlorine. This chemical system provided a useful method for calibrating the flow system for the accurate determination of small amounts of chlorine (