Systematic variation in the bimolecular rate constant, k(q), for the reaction of singlet oxygen and 1,4-dimethylnaphthalene has led to estimates of the Hildebrand solubility parameter, cohesive pressures and internal energies of vaporisation of some room temperature ionic liquids.

The final product from controlled-potential reduction of aqueous solutions of trans-[Rh(en),CI,]+ (where en = ethylenediamine), under an argon atmosphere, has been shown to be trans-[Rh(en),H (OH)] +. The pseudo-acidbase equilibrium (i) is shGwn to operate in solutions which are strongly alkaline (pH > 12). In the absence of bury, Kent RhITLH + OH-RhI + H, C> (0 oxygen, aqueous solutions of trans-[Rh(en),H(OH)]+ are stable toward both acid and base (0 < pH < 12) a t room temperature : in the presence of oxygen, no reaction is observed in acidic sclutions whereas rapid reactions are observed in basic solutions, giving initially the hydroperoxorliodium(rr1) complex [Rh(en),(OH) (OOH)] +, which on concentration yields the blue superoxo-bridged rhodium(ll1) dimer [(H,O) (en),Rh0,Rh(en),(H,0)]5+.Mechanisms of these reactions are discussed.THE rates of halide exchange in tmm-[Rh(py),X,]+ reduction of tvni?~-[Rh(py),~X,]~ has been shown to (X = C1 or Br) have been found to be markedly in-give unstable RhIII-H species2 which in this case hibited by traces of 0xygen.l It thus seems probable Attempts t o that these halogen exchanges involve catalysis by some reduced species (containing either RhIII-H or RhI) Vaughan, Chem* which also reacts rapidly with oxygen. Chemical 2 I<. D. Gillard atid G. Willtinson,

The study of adsorption is important for an understanding of such processes as heterogeneous catalysis, chromatographic analysis, and the dyeing of textiles. However, there are few simple and easily performed experiments available to illustrate the quantitative aspects of adsorption.1 The purpose of the present paper is to describe a simple experiment to illustrate the adsorption process from solution and its quantitative treatment using the Langmuir adsorption isotherm. Also, the constants of the Langmuir adsorption isotherm, for example, the limiting amount adsorbed by the adsorbent, may be evaluated, and this in turn allows an approximate evaluation of its specific surface area.Furthermore, the use of sand as an adsorbent in this experiment has an important potential environmental application. Effluent from plants in the dyeing industry contains highly colored species as well as appreciable quantities of materials with a biological oxygen demand (BOD) and suspended solids. Water pollution regulations now require treatment of these wastes prior to discharge. Whereas biological treatment processes are generally efficient for BOD and suspended solids removal, they are largely ineffective for removing color from the waste. The discharge of highly colored waste is not only aesthetically displeasing but also hinders light penetration and may in consequence upset biological processes in a river. In addition the dyes may be toxic to some organisms and hence cause the destruction of aquatic communities. The most commonly used adsorbent for treatment of textile effluents is activated charcoal, but this is relatively expensive. However, sand is a cheap and commercially available material that may have potential in the treatment of effluents. Experimental ProcedureThe adsorbent used in the experiment was ordinary brown "Builder's sand", which was first sieved to remove particles of diameter > 1 mm. The sand was then washed several times with copious amounts of water and finally dried in an oven at 100 °C, Recommended Volumes of Solution*

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A thin-film composite metal electrode is described for the amperometric measurement of hydrogen peroxide. By thermally evaporating a 27pm layer of gold/palladium through a copper mask onto a plastic substrate a number of chemically equivalent sensing elements can be prepared. On these electrodes, hydrogen peroxide can be oxidized at a voltage of 0.4V (SCE). A model for the oxidation of peroxide at these electrodes is described based upon revers.ible binding of hydrogen peroxide to electrochemically generated palladium oxide sites.