Tables 525-527. 



COLLOIDS. 



407 



TABLE 525. — Adsorption of Gas by Finely Divided Particles. See also p. 439. 



Fine division means great surface per unit weight. AH substances tend to adsorb gas at surface, the more the higher 

 the pressure and the lower the temperature. Since different gases vary in this adsorption, fractional separation is 

 possible. Pt black can absorb 100 vols. H2, 800 vols. O2, Pd 3000 vols. H2. In gas analysis Pd, heated to 100°, is used 

 to remove H2 (higher temperature used for faster adsorption, will take more at lower temperature). Pt can dissolve 

 several vols, of H2, Pd, nearly 100 at ordinary temperatures; but it seems probable that the bulk of the 100 vols, of 

 H2 taken by Pt and the 3000 by Pd must be adsorbed. In 1848 Rose found the density 21 to 22 for Pt foil, but 26 for 

 precipitated Pt. 



The film of adsorbed air entirely changes the behavior of very small particles. They flow like a liquid (cf. fog). 

 With substances like carbon black as little as s per cent of the bulk is C; a liter of C black may contain 2.5 liters of 

 air. Mitscherlich calculated that when CO2 at atmospheric pressure, 12° C, is adsorbed by boxwood charcoal, it occu- 

 pies i/s6 original vol. Apparent densities of gases adsorbed at low temperatures by cocoanut charcoal are of the same 

 order (sometimes greater) as liquids. 



See Langmuir, J. Am. Ch. Soc. 40, 1361, 1918; Richardson, sg, 1829, igi6. 

 TABLE 526. — Heats of Adsorption. 



* Small calories liberated when i g of the adsorbent is added to a relatively large quantity of the liquid- 

 t Volume adsorped from saturated vapor by i g of fuller's earth. 

 Gurvich, J. Russ. Phys. Ch. Soc. 47, 80s, 191S- 



TABLE 527. — Molecular Heats of Adsorption and Liquefaction (Favre). 



Smjthsonian Tables- 



