Ross reference electrode

The Ross reference electrode differs from the others and consists of a platinum wire immersed in a solution containing tri-iode and iodide ions. The Pt electrode responds to the redox potential established by the iodine(tri-iodide)-iodide couple. This solution is separated from the sample by a bridge electrolyte, which is 3 M KCl. 

At each well and depth, concentrations of dissolved oxygen, Fe(II), NO " and NO2 were measured. ORP s at Pt and WIG electrodes were measured against a Ross reference electrode. A Ross combination electrode was used to determine pH. Temperature and conductivity were also recorded. The detection limits for Fe(II) and N were 0.05 mg Fe or N per liter, and accuracies for each were +/- 10%. Sulfide was not measured, but no H2S odor was discernable in any sample. More detailed descriptions of the sampling and analytical methods will be published elsewhere. 

The reference electrode in the Ross combination electrode is Pt 112,1. This electrode is claimed to give improved precision and accuracy over conventional pH electrodes [R. C. Metcalf, Analyst 1987,112, 1573]. 

A Ross reference cell is used for ORP measurements, with its potential calibrated after each reading using Light s solution ( ). Platinum electrodes were carefully pretreated (0 and kept in an oxygen-free solution for at least ten hours before each run, since initially adsorbed oxygen at the Pt electrode surface can give erroneous potential measurements for up to two hours, even in anaerobic systems (0. 

A system somewhat similar to that of Hubbard was built by Yeager et al. [17, 18] and is shown schematically in Fig. 5. This uses a flat electrode and a thin layer cell as in Hubbard s first design, Fig. 2, but has two separate chambers for electrochemistry and UHV analysis, the sample holder being transferred between two transfer rods and a manipulator. This allows the use of a carousel on which several electrodes may be mounted. Ross and Wagner also adopted a thin layer configuration for the electrochemical cell [12, 19] with a palladium/hydrogen counter/reference electrode. 

This chapter will describe the iodine-iodide electrode with respect to properties that are relevant for practical applications, i.e., as a reference electrode for potentiometry as typically used in measuring chains with pH glass electrodes, which was introduced by Ross [164]. 

FIGURE 5-7 The alkaline and acid errors of several glass pH electrodes. A, Corning 015/H2SO4 B, Corning 015/HC1 C, Coming 015/1 M Na+ D, Beckman-GP/1 M Na+ E, L N BlackDot/lM Na+ F, Beckman E/1M Na+ G, Ross electrode. (Reproduced with permission from reference 16.)... 

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