GI 1x1, UKIridium oxide electrodes formed by potential cycling in dilute acids were investigated for their use as pH sensors. It was shown that both the short-and long-term stabilities of such sensors were adequate for applications where an accuracy of k0.2 pH is acceptable. It was also found that thicker oxide films which give responses of up to about 80 mV pH-' are to be preferred in order to ensure reproducible behaviour. As potentiometric probes either for direct monitoring of pH or for following typical acidbase titrations, these electrodes give comparable results to those obtained with glass electrodes. Several basic concepts relating to the practical management of potential-cycled iridium oxide electrodes are discussed.

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This study demonstrates the rationality of the use of isotonic PMS in children with respiratory infections, a condition regularly encountered by most pediatricians.

The electrochemical behavior and the analytical utility of hydrous oxide films, formed on iridium by voltammetric cycling, have been studied by evaluating the dependence of the apparent Standard Electrode Potential (E"' ) and the ratio of protons to electrons (p/e> participating in the potential determining equilibria on the charge storage capacity. A model based on electron exchange involving protons in solution and conductive sites on the hydrous oxide surface is proposed and it is shown that an increase in population of the conductive sites can be correlated with an enhancement in proton exchange capacity. The influence of the pretreatment is shown to be an important factor in determining both EO'and p/e. The implications of these results for the use of hydrous iridium oxide electrodes as potentiometric pH sensors are considered.