Fig. 6. Oxygen yields in a series of measurement run. Open, red, and gray rectangles denote NBS18, IAEA-601, and 602, respectively. Solid and open triangles denote quartz (NBS28) and montmorillonite (SWy-1, TKN-01, -29, -31), respectively. Dashed line represents the 92.8% yield as the average values for benzoic acids (IAEA-601 and -602).