640 



TABLE 693.— MASSES, VELOCITIES, AND RATES OF INCIDENCE OF 



MOLECULES* 



i/j = rate of incidence of molecules per cm 2 per sec, at 0°C and 1 microbar. 

 v v = rate of incidence of molecules per cm 2 per sec, at 0°C and 1 mm. 

 d = mass of gas corresponding to vi (g cm -2 sec" 1 ). 

 Gv = mass of gas corresponding to v x , (g cm" 2 sec" 1 ). 

 m= mass of molecule in grams— 1.66035 X I0' u M ; M = molecular weight; pi° 



= density (g cm" 8 ) of gas at 0°C and 1 microbar. 

 v a = average velocity (cm sec" 1 ). 



* For reference, see footnote 219, p. 636. 



** Calculated from the value p (density) = 1.293 X 10" 3 at 0°C and 760 mmHg. 



t Since the vapor pressure of mercury at 0°C is 1.85 X 10"' mmHg (=0.247 fib), the values given in 

 parentheses have no physical significance. Actual values at 0°C, corresponding to saturation pressure, are 

 as follows: p = 21.79 X 10- 10 ; v = 2.777 X 10 18 ; G = 9.249 X 10-°. 



TABLE 694.— MOLECULAR VELOCITIES 220 



C c 



Root mean square Average 



Gas velocities, NTP velocities, NTP 



Hydrogen 18.38X10* cm/sec 16.93X10 4 cm/sec 



Helium 13.11 12.08 



Water vapor 6.15 5.65 



Neon 5.84 5.38 



Carbon monoxide 4.93 4.54 



Nitrogen 4.93 4.54 



Ethylene 4.93 4.54 



Nitric oxide 4.76 4.38 



Oxygen 4.61 4.25 



Argon 4.13 3.80 



Carbon dioxide 3.93 3.62 



Nitrous oxide 3.93 3.62 



Krypton 2.86 2.63 



Xenon 2.28 2.10 



Mercury vapor 1.84 1.70 



Air 4.85 4.47 



Ammonia 6.33 5.82 



220 Newman and Searle, The general properties of matter, Edward Arnold & Co., London. 



MITHS0NIAN PHYSICAL TABLES 



