APPENDIX. 



439 



The following additional adsorptio- tables (see page 407, Table 525) may be of use in the "cleaning-up 

 of vacua." See Dushman, General Electric Review, 24, 58, 1921, Methods for the Production and Meas- 

 urement of High Vacua. 



TABLE 581. — Adsorption of H and He by Cocoanut Charcoal at the temperature of liquid air. 



For the preparation of activated charcoal see Dushman, 1. c. 5 g of charcoal at the temperatiu-e of liquid 

 air will clean up the residual gases in a volume of 3000 cm^ from an initial pressure of i bar (bar = i dyne/cm^) 

 to less than 0.0005 bars at the temperature of liquid air. 5 grams cleaned up 3000 cm^ of H from an initial 

 pressure at room temperature of o.oi bar to a final pressure at liquid air temperature of less than 0.0004 bar. 

 The clean-up is rapid at first but then slower taking about an hour to reach equilibrium. The figures 

 of the following table are from Firth, Z. Phys. Ch. 74, 129, 1910; 86, 294, 1913. p is in mm of Hg; v = vol- 

 ume adsorbed per g of charcoal reduced to 0° C and 76 cm Hg. 



TABLE 582. — Adsorption by Ch rcoal at Low Pressures and temperatures. 



Extrapolated by Dushman from Claude, see 1. c, and C.R. 158, 861, 1914. Amounts occluded in terms 

 of volume measiu-ed at i bar, 0° C. e.g. at a pressure of o.oi bar, i g charcoal woxild clean up 130 cm^ hydro- 

 gen or 18,000 cm^ nitrogen from a pressure of i bar down to o.oi bar. 



TABLE 583. — Adsorption of Hydrogen by Palladium Black. 



Palladium, heated, allows hydrogen to pass through it freely; the gas is first adsorbed and then diffuses 

 through. For the preparation of palladium black, see reference at top of page for Dushman. The following 

 data are from Valentiner, Verb. Deutsch. Phys. Ges., 3, 1003, 1911. Different samples vary greatly. P gives 

 the pressure in mm of Hg, and V the volume at standard pressure and temperature per g of palladium black. 



Smithsonian Tables^ 



