Conditions which maximise silver( \)-olefin interactions are not suitable for obtaining comparative equilibrium data. Measurements of ethylene absorption efficiencies a t 20 "C (C,H,:Ag' ratios) in aqueous silver(1) nitrate, trifluoroacetate, and perchlorate solutions are reported over a pressure and concentration range and with added acid and sodium salts ; some results are also given for glycol solutions. The trends in absorption efficiencies are correlated with silver( I)-anion interactions in competition with silver(i)-solvent interactions and with the structuremaking influence of ions on the solvent. Single effects cannot explain the experimental observations. Some previous results are reinterpreted, making allowances for anion and solvent effects.THE interaction of silver(1) cations with olefins has been studied e~tensively,l-~ Practical and theoretical objectives, respectively, have been to attain an optimum efficiency in the separation and purification of olefins, and to correlate the extent of silver(1)-olefin interaction with the olefin structure. These objectives are conflicting in that the former requires concentrated solutions of silver(1) salts to niaximise the olefin absorption in a given volume, whereas the latter requires dilute solutions to calculate true equilibrium constants. Any review of the literature soon reveals that measurements of the latter kind have been made at comparatively high concentrations of silver(1) salts and that extrapolations to zero concentration have neglected, or incorrectly allowed for, the effect of the counter-ion. Structural differences between silver(1)-olefin complexes deduced from non-comparable formation constants can lead to dubious theory. Theoretical calculations *y5 have also tended to oversiniplify the situation by neglecting interactions other than the silver(1)-olefin interaction. In this paper a more detailed study of the factors influencing the complexing of silver(1) by the

43, 979. 470.Methyl cyanide, MeCN, was finally dried with CaH, before fractionation. Sulphuric acid was adjusted to a minimum conductivity with oleum. Materials were manipulated under dry nitrogen in a glove-box or in special glass vessels. Silver was determined by Volhard's titration, acidic hydrogen by alkalimetry, sulphate as Ba[SO,], and metals gravimetrically or by ethylenediaminetetra-acetic acid titrimetry.

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