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Uncoated quartz or glass vessels

At 540 °C with a silica bulb of about 250 cm capacity, the dependence of the rate of reaction on the pressures of hydrogen, oxygen, and [Pg.16]

The autocatalytic nature of the reaction, described by Hinshelwood and Williamson [1], is in sharp contrast with the effect of water on the surface reaction at lower temperatures, which is poisoned by steam, and also with the inhibiting effect of water vapour on the second limit explosions. The autocatalysis has been studied in some detail by Chirkov [36], who used a reaction vessel of Durobax glass with diameter 5 cm and volume 200- 250 cm. For hydrogen oxygen ratios of about 2 1 at 550 torr initial pressure and 524 °C, he found the reaction rate w (torr sec ) to be given in terms of the initial pressure p and the amount of gases reacted x by [Pg.17]

When the concentration of hydrogen was low, the same expression was found, but with p and x now representing partial pressures of hydrogen, i.e. [Pg.17]

A further pair of experiments by Chirkov elegantly illustrates the part played by the water vapour. In one of these he measured the reaction rate for a 2H2 + O2 mixture at 493 °C and 597 torr initial pressure while, in [Pg.17]

Diameter (cm) Rate, 600 torr Rate, 300 torr (V(00 30o)/d (t 600 V3oo)/d [Pg.18]


The reaction is autocatalytic, resembling in this respect the situation already encountered with uncoated quartz or glass vessels. However, in contrast with the results of Lewis and von Elbe [23] for a quartz vessel, Baldwin and Mayor [45] found little or no effect of addition of up to 22 torr added water on either the induction period or the maximum rate, irrespective of whether the water was added a short time before, or together with, the reactants themselves. They concluded that the autocatalytic effect cannot be due to poisoning (by absorption of water vapour produced in the reaction) of the ability of the surface to destroy chain centres, as had previously been suggested. [Pg.46]


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