Practice of Kinetics (Comprehensive Chemical Kinetics, Volume 1)

2 THE SOLID-GAS INTERFACE 219glyptal to seal pin holes round the windows, although the design permits bake-outof the sample to 600" C. ONeill and Yatesi7' have described a similar design,with magnesium oxide windows directly sealed to soda glass, permitting the completecell to be heated to 400" C and eliminating the use of ground joints.A cell for combined infrared-ultraviolet spectra devised by Leftin17 is shownin Fig. 23. The sample is mounted with platinum wire in a rectangular quartz cagewhich is a close fit in the quartz adsorption cell used to observe the ultravioletspectrum. The uv cell is sealed directly to a pyrex tube which connects with the IRcell at the other end. Sodium chloride windows are used for measurement of theinfrared spectrum. Provision is made for gas admission and evacuation and forheating of the sample by an external furnace.1 crn square PyrexNaCl Whdows0.9crnSample holder forspectral measurementsGr%ed seal -Sample frameIcrn square silica cellFig. 23. Cell for catalyst spectral studies in the infrared, visible and ultraviolet regions. From ref.173.Potassium bromide windows have been used by Boreskova et ~ 1 . l and ~ ~ byLiengme and Hall'75. The latter cell is a modification of the design by Littleet ~ 1 . ' Sample ~ ~ . discs can be moved between the IR windows and a furnace, withthe cell connected by a flexible metal tube to a vacuum and gas handling system.An identical IR cell is also placed in the reference beam. Because the gaseousatmosphere is present in both cells, it is automatically subtracted by the instrumentand only the spectrum of adsorbed species is recorded.References pp. 270-278