raise the temperature, luminescence will occur with an oxygen pressure of 583 mm. Hg. A somewhat analogous case is presented by the oxidation of pyrogallol solution in contact with ozone, except that in this reaction too high a concentration of pyrogallol will hinder the oxidation. I have not studied the effect of varying concentrations of ozone. If oxygen, passed through an ozonizer (the silent electric discharge tube), is bubbled through m/100 pyrogallol, no luminescence occurs at 0°, a fair luminescence at 20°, a good luminescence at 50°, and a bright luminescence at the boiling point. If the pyrogallol is of _m_ concentration, no luminescence occurs at 0° or 20°, a fair luminescence at 50°, and a bright luminescence at the boiling point. For a definite temperature, say 20°, no light appears if the pyrogallol is of _m_ concentration, but if we raise the temperature, luminescence can occur. The similarity to phosphorus is obvious. Thus the "maximum luminescence pressure" of pyrogallol increases with increase of temperature. We have already seen that pyrogallol can also be oxidized, if H_{2}O_{2} is present, by a great variety of substances, such as peroxidases of potato or turnip juice, hæmoglobin, KMnO_{4}, K_{4}Fe(CN)_{6}, CrO_{3}, MnO_{2}, hypochlorites and hypobromites, or colloidal Pt and Ag. For convenience we may collectively speak of these as oxidizers. They are recorded in Table 13. No light occurs if H_{2}O_{2}is absent. In the case of some of these oxidizers pyrogallol will luminesce in dilute concentrations but not in strong. Also, dilute pyrogallol will luminesce with a dilute solution of oxidizer but not with a concentrated solution of oxidizer. The effect of rise in temperature in these cases also is to increase the "maximum luminescence concentration" of pyrogallol and the "maximum luminescence concentration" of oxidizer. Table 11 shows this effect of temperature with K_{4}Fe(CN)_{6} and varying concentrations of pyrogallol, and Table 12 shows the effect of temperature with pyrogallol and varying concentrations of K_{4}Fe(CN)_{6}. Table 10 shows the relation between temperature and intensity of luminescence with pyrogallol and various oxidizers. The terms _faint_, _fair_, _good_, and _bright_ are purely relative designations of brightness as estimated by the eye, for accurate measurements of weak intensities are very difficult to make.