Doctoral Thesis Cover Page — page 15: what you’re looking at

Machine-transcribed from the original scan — historical spelling and the odd misread are preserved.

ADSORPTION OF GASES BY METALLIZED SILICA GELS 99 is due to change in gel structure alone, then on the basis of this ratio increase, the presence of silver in the gel has resulted in the specific adsorption of oxygen, carbon monoxide and possibly ethylene and methane. The adsorption values for the palladized gel are not strictly comparable to the other adsorptions because the silica gel which was used was from a second preparation of the gel. It shows distinctly greater adsorptive capacity for carbon dioxide. This may be attributed largely to gel structure since Taylor and Burns! have shown that palladium adsorbs carbon dioxide but shghtly. If we make this assumption then by comparison with the data on the first silica gel the gel containing the palladium should adsorb 2.63 c.c. of carbon monoxide, 0.74 ¢.c. of oxygen, 2.88 ¢.c. of methane and 20.90 ¢.c. of ethylene. We find good agreement between these calculated values and the observed results in the case of carbon monoxide and methane. Oxygen seems to be specifically adsorbed by the palladium and there is not much doubt that ethylene is very strongly adsorbed, since there is an adsorption of more than 5 c.c. above the calculated value. Specific adsorption of ethylene by the palladized gel is further indicated by the shape of the adsorption curve. More ethylene is adsorbed at low pressures than carbon dioxide while the carbon dioxide is more strongly adsorbed near atmospheric pressures. This type of curve 1s a characteristic of specific adsorptions. In the case of hydrogen the first experimental work indicated zero ad- sorption. This might be due to two separate factors. Either the drying in an atmosphere of hydrogen filled the palladized gel with hydrogen and this was not subsequently removed by the heating and evacuation, or the palladium surface had become poisoned as regards hydrogen adsorption. Taylor and Burns? have shown that palladium exhibits considerable reluctance in giving up hydrogen so that the first explanation is plausible. Additional work seems to eliminate this possibility in these experiments. Pollard? has shown that traces of grease poison platinum as far as adsorption of hydrogen 1s concerned. Accordingly, additional experiments were carried out using the utmost precaution to keep grease away from the palladized gel. The palla- dized gel then showed an adsorptive capacity of 0.76 ¢.c. of hydrogen per gram of metallized gel at o° and 760 m.m. pressure. <A repetition of the adsorption measurements decreased the adsorption to 0.55 ¢.c. per gram of gel. A second set of experiments was then carried out. The palladized gel was first heated in an atmosphere of nitrogen at 120°-140° for a period of four hours. It was felt that this might partially remove any adsorbed hydrogen. ‘The regular pro- cedure for adsorption study was then carried out. The adsorption determined in this experiment gave a value of 0.87 ¢.c. per gram of the metallized gel. This is so close to the value previously obtained that no further work was done on this phase of the problem. It would appear from these results that palladium is also very easily poisoned as far as hydrogen adsorption is concerned. An 1 J..Am. Chem. Soc., 29, 421 (1925). 2 J. Am. Chem. Soc., 43, 1273 (1921). 3 J. Phys. Chem., 27, 356 (1923). CONNICMOO @) S (C(O)