204 STUDY OF COPPER-GLI’COCOLL SULPHATES DISCUSSION. Dr. A. C. Cumming asked why the author had used 3.5 N sodium nitrate as the connecting solution in the electrometric measurements. It was his experience that it did not eliminate diffusion potential. Dr. F. G. Donnan, in reply, said that in the final experiments, on which alone conclusions were based, the diffusion potential was autoinatically eliminated because the solution on each side contained practically an equal number of current-carrying ions, The connecting solution had in this case no disturbing effect.