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3 Effect of Temperature on the Reaction

guaiac, pyrogallol, potato-juice and acid


A very faint light is produced when pyrogallol +

at 0°C. is mixed with potato-juice at 0° C. The light is much brighter at 5° and quite bright at 10° C. Pyrogallol + mixed with blood (1 per cent) gives no light at 0° C., but a very faint light at 2° C.

High temperatures destroy the pyrogallol oxidase of potato-juice. This occurs between 80° and 85° C., as indicated in table 23. The potato-juice was rapidly heated to the temperatures 50°, 55°, 60° C., etc., then cooled rapidly in running water. The destruction of cata lase, the formation of a precipitate in the potato-juice, and the effect on its power to blue guaiac alone, guaiac + and guaiac + ionized turpentine, are also recorded. Similar results were obtained with turnip-juice. Blood does not lose its power to oxidize pyrogallol +11202 with light-production or guaiac even after 10 minutes' boiling.

Note from table 23 that the pyrogallol and guaiac oxidases in pres ence of are both destroyed between 80° and 85° C., but that with ozonized turpentine the juice heated to 100° C. still blues guaiac faintly. The natural peroxide (oxygenase) of potato-juice, which disappears on standing, is destroyed more readily than the peroxidase. Catalase is destroyed between 55° and 60° C. before a precipitate has appeared, whereas peroxidase is still active after a precipitate has appeared.



In testing the effect of these substances, equal parts of (1 c.c. m/160 pyrogallol + 1 c.c. 3 per cent and (potato-juice + KCN or NaOH or HC1) were mixed. Table 24 gives also the effect of catalase on the bluing of guaiac + and the color of indicators added to deter mine the amount of acid or alkali uncombined with protein. Neutral red is red in neutral or acid solution, yellow in alkalies. "Di-methyl" is yellow in neutral or alkaline solution, red in free acid solution.

The concentration of acid and alkali added give, of course, no idea of the H-ion concentration in the potato-juice. The oxidase acts best in the region of neutrality or slight alkalinity, and Reed (4s) finds by hydrogen electrode measurements that the oxidase of potato is inhib ited in a The effect of the acid is reversible unless it has acted too long.

Note from table 24 that KCN affects the pyrogallol peroxidase in very weak concentration (m/2,000), but is not so effective in destroying catalase or preventing the bluing of guaiac. NaOH and HC1 are not so toxic. As we might expect, the HC1 is the more toxic of the two.